DESCRIP INORGANIC CHEM
DESCRIP INORGANIC CHEM CHEM 362
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Coordination Number Six Octahedral is a very important geometry It is the starting point for the shapes of most transition metal complexes 1 Regular octahedron all distances are EQUIVALENT 3 Distorted Octahedron Rhombic distortion a oat Lilli L 2 Distorted Octahedron axial distortion a qt b 4 Distorted Octahedron trigonal distortion Trigonal prism is not as stable as the regular octahedron because LL distances are not maximized in the trigonally distorted geometry This is a very rare geometry for ML5 complexes Higher Coordination numbers Seven Pentagonal Octahedron Trigonal bipyramid an prism extra an ligand extra ligand 1 L w Cube gt sguare antiprism twist of face rotate the corners of once face until it is 45 out of phase Cube gt dodecahedron pull corners away from each other Grab opposite ends amp pull up amp down 244 Nomenclature of Coodination Complexes Follow IUPAC rules veg speci c Examples 1 mer Trichlorotris triphenylphosphine Rhodium I 2 potassium tetrabromocuprate II 3 trans Dichlorotetraaquachromium II chloride key aspects of these names 1 pre x cis transmerfac 1 de ne 2 Which ligands come rst in a mixed ligand complex 3 Which type of pre x bi bis tri tris tetra tetrakis etc 245 4 oxidation state of the metal 5 Special issues such as 0 Optical isomers 0 Bridging vs nonbridging o Endings for ligands CC 939 CC 1te 1de ate 0 0 Special names for ligands 0 Charge on the compound Book gives 11 rules Distill them down No spaces in name except if it is a salt put a space between cation and anion and cation is rst 246 Name is organized according to Anionic LigandsNeutral LigandsCationicLigands Metal NameOxidation state of Metal Within these categories we must establish rules of a alphabetical order b prefixes and suffixes for ligands c suffix or not for the metal Prefixes m Suffixes m use di tri etc 11 b15 unless the ligand Tr1 tr1s name already has Tetra tetrakis one of these as part Penta pentakis of it s name Hexa hexakis then use bis tris etc Suffixes a anionic ligands Hato ide gtido ite gtito 247 end in o acet gt acet nitride gt nitrido sulf1te gt sulf1to CH3COZ39 acetato b neutral ligands same as molecule name with a few N339 nitrido SO32 sulf1to exceptions NH3 gt ammonia H20 gt water NO gt nitrogen monoxide MNH3 ammine MOHZ aqua MNO nitrosyl CO gt MCO carbon carbonyl monoxide c organic groups keep same name CH3 MCH3 Methyl methyl CsHs MQ phenyl d metal suffix i if compound is neutral or cationic RuL53 no suffix ruthenium gt ruthenium ii if compound is anionic then metal name is changed to ate ending RuL5339 ruthenium gt ruthenate Within each category of ligand alphabetize the ligands within each group if more than one type is present anions rst neutral second cationic third NOTE don t count bi tri etc in alphabetiZing 24 9 Metal oxidation state is written in parentheses in Roman numerals at the end Special Characters and abbreviations a Geometrical isomers cis trans X vsX facmer X X M vs M X X X 250 b optical isomers use symbols A and A c bridging ligands CI use prefix u M M Cmu77 if two of the same kind Cl diu di uCl M M Cl MNOZ39 nitro MONO39 nitrite a H20 hydrate Water can be in a formula like this MCI6nHZO Number of water molecules of hydration 0 H20 monohydrate o 2H20 dihydrate etc Now start practicing 251 cation anion EX 39 four two neutral anionic ligands ligands dichlorotetraaquachromiumHI chloride four ligands four ligands cation anion EX 2 PtpY4 PtC14 tetrapyridineplatiniumll tetrachloroplatinateII normal ending ate ending molecule is neutral EX 3 PtacacNH3Cl T T T Anionic neutral Anionic ligand acetylacetonatochloroammineplatinumII 252 cation anion EX 4 KFeCl4 Fe is Felll T anionic ligand potassium tetrachloroferrateIII iron is not written as ironate neutral ligand i EX 5 C0en32SO43 Cation anion Ratio of cation to anion is 23 three ethylenediamine en ligands trisethylenediaminecobaltIII sulfate 253 water i EX FCH206BT2 cation anion hexaaquaironll bromide neutral anion cation anion chloropentaamminerhodiumlll chloride Practice drawing the structure based on a formula mertrihydrotristriphenylphosphinerhodiumlll H T PPI13 m is 3 gTOUPS Ru around the perimeter P39hglj l R H PPh3 factrihydrotristriphenylphosphinerhodiumlll 254 Stabilitv of Complexes in Solution Stepwise formation of metal ligand complexes involve Equilibria K 2 ML 1ML ML 1 MllL MLz 2MLELlt gtML2 K2m j ML6 6ML5Llt gtML6 K m Six equilibria are involved in the formation of ML6 from M and 6L Each K is a stepWise formation constant Concentration of L determines the relative concentrations of products Overall rather than stepwise Equilibrium Constants are ML 81ML MLZ M2L lt gtML2 z MLz MLg M 3L H ML3 3 MirLr 1amp6 M6L lt gtML6 s ML6 Take B3 for example ML3 MLHMLz 3 3 multiply ML MLML21 num amp rearrange denom by 3 ML MLz ML3 this really ML MLllLl MAIL just 1 257 Then B3 K1 K2 K3 or the product of all three stepwise Equilibrium Constants in general BK KlKzK3 Kk 39 overall formation stepwise formation constants constants Usually Ki decreases with each subsequent step As ligand is added to the metal ion M M L forms first then when more ligand is added MLZ rises sharply amp ML drops With more added L MLZ drops and ML3 rises etc etc Since the ligand addition to form a new compleX is always reversible an ML11 progresses with greater n values there are more ligands to fall back off and fewer places to put the new ligands in the coordination sphere so it is expected that Step wise Ki s would drop 258 Cd NH3 H CdNH32 K1 10265 Cd NH332 NH3 H CdNH342 K4 10093 formation of CdNH342 illustrates the drop in equilibrium constant with added L groups Q What are formation constants useful for A Separation of ions in the presence of each other EX EDTAZ39 selectively pulls CO2 out of water in the presence of more highly charged cations such 4 as Th Mm DOC CH2 ch coo quot30f H2 E N I quot 0 J W quotDOC CH2 EDTA H2Ci COO The hexadentate ligand wraps itself around the Co2 center EDTAZ39 has less affinity for the 4 cations EDTAZ39 brings up another important stability issue namely the Chelate Effect 259 INH3 versus HZN NH2 H3N NH3 versus M HN NH 2 2 the vemembered nng formed here is much more stable than the independent Why NH groups To reverse the reaction of M en is more dif cult than for Mn2NH3 If one of the NH groups falls off there is still another bond to hold it onto the metal H N NH H2N NH2 2 2 M easy to reverse partial dissociation 2 2 NH3 H N NH NHZ H2 3 N39 3 HZN UI I N I Ni HsN I NH3 HZN I NH3 LNHZ 2 B6 2 1086 B3 2 10183 Nien32 is 1010 times more stable Q Why The bonds are very similar A AG is affected by enthalpic and entropic contributions AG 2 RTan 2 AH0 TAS l recall in the NiNH362 vs Nien32 case we can perform a reaction and determine K NiNH362 3en H Nien32 6NH3 2 chelate complex K 1097 AG Rtan 67kJmol AH TAS 67 kJmol Ifwe know that AHquot is AHquot 12 kJmol Then TAS 55 kJmol Note both enthalpy and entropy considerations favor the chelate complex but the entropy effect is much more important Bottom line The Chelate Effect is Essentially an Entropic Effect In order to understand this Ni rxn must be examined in more detail NiHZO62 6NH3 gt NiNH362 6H20 The number of particles hasn t changed from Reactant to products 7 in both cases 262 NiHZO62 36 Nien32 6H20 4 particles 7 particles to the right gt is more disordered Reactivity Patterns of Coordination Compounds Covers a very large number of issues in transition metal chemistry Main ones to be highlighted in this course 0 Substitution 0 Electron transfer 0 Isomerization The correlation of these reactions with electronic and molecular structure is the essence of much of inorganic chemistry 263 Octahedral Complexes Substitution chemistry 1 Labile ligands that are easily substituted Lability refers to the ability of a coordination complex to lose one or more of it s ligands with others in solution 2 Inert refers to the lack of ability of a coordination complex to lose one or more of its ligands with others in solution labile vs inert is not the same as unstable vs stable Stability refers to the tendency of a species to exist Thermodynamic issue 264 Labile vs Inert is a Kinetic Issue CoNH363 is not a very stable compound thermodynamically judging by CoNH363 6H3o a CoH2063 6NH4 K 1025 for left to right But the reaction takes months because inertness of the compound The reaction is veg slow Working de nition of inert and labile labile reactions ltl minute halflife over in time of mixing inert reactions gtl minute halflife can easily be studied by conventional means 265 Two Tvpes of Ligand Substitution 1 Associative A additionelimination 2 Dissociative D A 1 L5MX YSIOJ L5MXYfa Stgt L5MY X 7coord intermediate Y directly binds before X leaves D 2 L5MX 31 L5M X L5MY X 5coord intermediate In both cases the rst step which is slow is rate determining A is bimolecular process D is unimolecular process 266 A amp D are just extremes of What can really happen Associative may not involve a real 7 coordinate intermediate Some degree of bondbreaking to X and bondmaking to Y is happening in the intermediate or transition state complex Dissociative likewise may also have most of the MX bond broken but not all before the near MY bond forms Real life is rarely simple r Lsxv quot b H 1 3 n 1 Y L 3 my x Radian we39detlquot Dssodwlive LID anwdarge 13issacia 39ve amp Ist X qS9 Elf M650 dim 9 268 1 WA x W T A r l quot W fmsYJ x Nadia madam 9 AssociaJive WWW 0va t l5Hx T r 01 st I 0 s x 269 Types of Reactions in Octahedral Metal Complex Substitution Chemistry l Solvent interactions 2 ionpair formation 3 conjugatebase formation 4 anation reactions 5 aquation reactions acid base hydrolysis 6 ligand assisted reactions SquarePlanar Substitution Reactions 1 charge effects 2 steric effects 3 entering ligand effects 4 stereochemistry 103 3 VSEPR Model Xalence hell Electron Pair Repulsion Theory Electron pairs will tend to stay as far apart as possible to minimize repulsions l Bonding Pairs B 2 Lone Pairs E 3 Central Atom A For A PX Ey which is the general notation X of B pairs y of Lone Pairs 4 Occupancy factor X y Total number of electron pairs 104 Repulsions increase in the order Bonding Pair Bonding Pair Bonding Pair Lone Pair Lone Pair Lone Pair Q Why A Bonding Pair electrons are diffused through orbitals of AB ABXEy m 2 3 4 Basic Geometry Hybridization Linear sp Triangular sp2 Tetrahedral sp3 sd3 Square planar dsp2 Square pyramidal dsp3 Trigonal bypyramidal dsp3 octahedral dzsp3 105 Maw 91va may 86 Chapter 3 Structure and Bonding in Molecules Figure 37 LEAHCd ut39IumLI39IM Em sll39lu lm39w mung hr ifll1LlB l39 quotHz u 11ltlt39139H 1 awll 1 u39r39nI39qllu39ru mmm Il39n 1 Hr Enm39 palm Ic39mimg nu i M 39 5 M ll 39 g sniplizm ux391hrmnlliplnImuris nwl CRIil Ruljlmmlt s O 106 For every basic geometry type there are different ways to achieve same occupancy factor X y in the ABXEy formulae occupancy of 2 AB X 2 y 0 lin H Be H o sp hybridized C QCQ z OCO 180 sp hybridizedN NNN z N N N 180 ABE X 1 y 1 lin C O Sp CO zcNz39 sp C N occupancy of 3 AB3 z b 2 sp2 hybridized C ZOCO 120 y sp2 hybridized N bent quot 39 9 z ONO 115 y N sp3 hybridized N Z o tetrahedral H3C l CH3 C N C 109 CH3 107 AB3E x3 P C y 1 H30 H3 sp3 hybridized P trigonal CH3 1 CPC 99 pyramid ABZEZ X 2 O y 2 H H sp3 hybridized o rm 1 HOH 1040 ABE3 X u presumably sp3 y 3 H30 o hybridized O lin 39 39 although with lone pairs it is hard to know where they really are in space 109 occupancy of 5 A35 X 5 Cquot y O I 9quot dsp3 hybridized P trigonal QI PH Z ClPCl 1200 bipyramid 9 in A plane tbpyk 90 g AB4E X 4 39F39 y Z 1 181 sawhorse I F AB3E2 39F39 X 3 y 2 IC Tshaped I IE2 L4 is quot dsp3 hybridized S F 1 FSF 103o dsp3 hybridized C1 J E 87 0 gt note that tbp is the most common AB5 basic geometry 110 occupancy of 6 AB6 z39F39 F6 1FF 2 3 y 0 S d sp hybr1d1zed S octahedron ABSE X 5 y 1 dzsp3 s uare zF hybridized Br pyramid quot 1F quot AB4E2 X 4 Cl C3 y 2 dzsp3 hybridized 1 s uare planar quot 111 Summary of main types of Hybridization amp shapes of orbitals 1 sp linear 2 sp2 trigonal planar 3 sp3 tetrahedral 4 sd3 5 dsp2 6 dsp3 a dzzsp3 trigonal bipyramidal b dgtlt2y2sp3 square pyramid 7 d2sp3 octahedral Occupancies for Sp 2 2 dsp2 4 Occupancy is sp2 3 dsp3 5 hOW many SP3 2 4 d25p3 6 orbitals you Sd3 4 are using 112 Main Point Armed With 1 An understanding of how to draw Lewis structures 2 How to determine occupancies of a molecule bonding lone pairs We can use 1 and 2 to predict structures by both the Hybridization and the VSEPR methods amp correlate them Process of applying Lewis structures VSEPR and Hybridization 1 Determine the Lewis Structure Diagram 2 Determine occupancy factor xy 113 3 Determine how many hybrid orbitals you will need same as xy and choose type of hybridization a use only s p orbitals for elements in rows 12 elements below Ne which is 10 b sp and d orbitals are all available after row 2 c note that multiple bonds can be made from unhybridized orbitals 4 from the occupancy factor xy determine a basic geometry type After arranging the Bonding Pairs and Lone Pairs determine the actual geometry of the molecule 114 Example 1 SF4 1 Lewis Structure A S 6 e39 6 e39 B F 7 e39 X 4 amp39 34 e39 3939 2 AB4E 39 F 39 occupancy 5 3 for an occupancy of 5 with d orbitals available we have dsp3 hybridization 115 5 for an occupancy of 5 AB4E one can either a trigonal bipyramid or square pyramidal pr is by far the most common so tbp is the Basic Geometry but sawhorse is actual structure with the atoms 15 T F angle is lt 1200 F U because of lpbp repulsion being greater than bpbp 198 Hydroxides MOHS nH20 gt Maq OHaq for metals with more ionic bonds gt Base MOH nHzO M01301 H30aq for more covalent MO bonds of the nonmetals gt Acid Amphoteric Hydroxides also exist Alkoxides The basic formula of an alkoxide is OR39 Where R is an organic group such as an alkyl group They are very reactive in water and hydrolyze quickly OR39 H20 2 OH39 ROH forms an alcohol 199 MOR4 is a common metal alkoxide type of compound or we also say compleX eg TiOR4 It has an interesting molecular structure that stabilizes the molecule 0 0 000 I Ohl l 0 These 39M39 M represent 0 l 0 l 0 OR39 groups 00 00 O M M 0 I O I O O O the more bulky R groups on GR ligands lead to compounds with low coordination numbers MOR4 when R Me Et MOR2 when R 235tritetrabutylphenoxide 200 Poanuclear or Poleeric OxidesHydroxides dimers trimers cages etc cyclic structures chains sheets Poanuclear OX0 Anions oxygen atoms shared between various polyhedra EX 1 dichromate 2 06 0 quot x Dimer Cr Cr 03939 l l Cf207 O 0 two tetrahedra sharing one atom tetrahedra sharing an edge Ring anion Si309639 EX 3 tetramer B405OH4239 m Si03239 OH oBo HO B O B OH o Bo OH Common anion in borates 202 Basic Idea Silicates are minerals composed of different types of shared SiO4 units Borates are minerals in the same vein but with B04 units shared in various ways The structure that results is based on a complicated interplay of concentrations pH temperature and pressure which affect solubilities Eventually if all oxygens are shared in a SiO4n39 solid it becomes silica SiOz replace some Si4 ions with Al3 and it is possible to make structures like the silicates except the anion charge is retained Si02 neutral SiAlOz is negatively charged SiAlOz39 gt Aluminosilicates Minerals with open frameworks that can allow molecules to pass through 203 Ion exchangers solution Molecular sieves gas Zeolites AlSiOz11 framework Basic composition of Zeolites is MmA102XSiOZy z H20 number Of Charge 0f number of A10 units metal cation 3102 units z degree of hydration lots of water can ll void space Si205239 sheets Si atoms are in a plane connected by 3 oxygen atoms to give a hexagonal motif one oxygen on each Si is not used to bridge terminal 0 coming out of plane bridging O Si atoms in Model of a zeolite showing the channels in the structure The spheres are 0 atoms The Si and A1 atoms lie at the centers of the O4 tetrahedra and cannot be seen Polynuclear OX0 Anions continued 4 Polyoxoanions of Transition Metals VV NbV Tav Mo WVI form anions With shared M06 octahedra Where corners and edges are shared Excellent example is CrMost4H6339 F gure 55 hr m unm ryl Icmrlnhnn nh quot The ind g pl lvlmhly bound 0 L Lcn munh at am cenml mmmdnm u mm are 207 Miscellaneous oxo anions that are worth mentioning speci cally because they are ubiquitious are as follows Carbonbased cof39 HCO339 0x 0 coordination modes 0 MOCO 00 M O Nitrogenbased NOz39 nitrite NO339 nitrate Various binding modes are depicted on page 152153 of textbook M M o M M 0 M B70 039 H N U 3 1X 57X 7 O M N0 M Na 0 39 FrX39III BVXIV SVXV Sulfurbased 803239 sulfite HSO339 bisulfite 504239 sulfate HSO439 bisulfate S s 0 0 0 1 t 39 L 0 39v quotuXYIII M n O is 0 0 M II Phosphates Also important in chemistry as discrete anions and in condensed polymeric phases as minerals O Oquot PO4339 binds as an end unit one of four resonance at one 0 forms binds as a middle unit binds as a branching unit 210 These Building Blocks can assemble into linear or cyclic structures 3 O O 5 P O O O o o 0ll0llOIlo 0 lo P P P gtP P l I l O O O O O O P309339 P30105 metaphosphates polyphosphates widely used as water softeners due to their ability to stabilize Ca2 Mg2 and other ions that make water hard MgCOg CaC03 scum Other types of Oxo Anions o HalogenContaining Anions HalogenOxides l XO339 halates X formal ox state eg 005 chlorate 2 XO439 perhalates X formal ox state ClO439 perchlorate is most wellknown 211 XO439 not particularly stable especially as in the perchlorate anion ClO439 gt these are strong oxidizing agents stabilized in water dangerous When dry and especially with organic compounds around 0 Transition Metal Oxides Discrete Tetrahedral M041 is very common for the highest oxidation state of the metal or next to highest e39g39 OSO4 OSWhat is formal R604 Re ox state Excellent MnO4 Mn oxidizing agents cr04 Cf Halides and Pseudohalides o Pseudohalides such as CN39 act like halides OCN39 SCN39 all are good ligands Most important one is cyanide CN39 C N Binds through C atom rst 0 Halides ionic versus covalent ionic are discussed in Chapter 5 covalent analogs are in Chapter 20 ionic halides are with metals in 1 2 3 oxidation states Sul de and Hydrosul de 0 8239 Ionic sul de compounds are formed with alkali and alkaline earth they are not stable in H20 0 811239 polysul des very important ligands for transition metals 213 Complex Anions Complex Halides AlC13 Cl39 AlCl439 l Lewis LGWiS Acid Base PF5 Fquot 39 PF639 general stability is F gt C1 gt Br gt1 due to strength of AF vs ACl interactions vs ABr vs AI Complex Transition Metal Anion s CN39 forms many complex anions in a variety of oxidation states from low to high FeHCN6439 versus MoVCN8339 214 Most of these anions are quite stable in H20 and indeed the acid form of some of them can be made without releasing HCN For example H4FeCN6 exists H is stabilized by Hbonding between molecules B Electron De cient less than an octet eg BeHz lBeH Be does not need an octet Total of 4 valence electrons Not the same as unsaturated systems that achieve the 8e39 octet through the formation of multiple bonds C Electron Rich greater than an octet Valence shell expansion occurs with elements beyond the 211d row s p 1 levels are all available 2e39 6e39 lOe39 gt total of 18e39 possible eg transition metals have expanded electron counts typically 18e39 referred to as valence shell expansion PCl5 P 5e39 5e39 Cl 7e39 x 5 40e39 Ci 0 Ioe39 around I P 9 W Paz om g4nonl aquot Cl anurJHuCl 15 Q What about transition metals A They tend to exhibit 18e39 valence shells full s p d levels They form bonds to lone pairs of molecules called ligands until they reach the 18e39 con guration EX Ni2 compounds Ni has 10 valence electrons it needs 4 bonds to reach 18 valence electrons NiCO4 is a compound that illustrates this point CO valence electrons 46 lOe39 Lewis structure is this one C E O to allow for an octet unsaturated CO can then act as a ligand with the lone pair of C bonding to the Ni atom R N A e f ONady ow OEc ll I C0 Wiferm T 4 4 bermxv NC 0 W show C E O The C lone pair is more basic donating than the O lone pair The ligand C E 0 is considered to be a Lewis base electron pair donor and the metal Ni is the Lewis acid electron pair acceptor The bonds formed in this way are coordinate covalent bonds gt The ligand supplies both electrons of the metal ligand bond CONH363 C034L 6 valence eedrma Gr J a xze mun hydjit39 I 1 H Nl z I H 315 I NH3 Nr 3 AIIH3 quotquot3 M mu M o 0 0 0 W 39 e oltgt N o 39 f 399 O 0 W I 739 Na 54mm is a mtt 1an so Q How did we justify the concept of resonance A Experimental evidence says that all the bonds are the same length in these molecules gt more of a delocalization model Summag of Resonance Hybrids I b 6 Bf 9 aNone of these canonical forms is an actual representation of the real structure These structures don t really exist but their average corresponds to the real structure bExperiment shows that all bonds AB are equal in length so theory and experiment correlate c The average hybrid structure has a lower energy than any of the contributing structures A special case of resonance is covalent lt gt ionic resonance AB lt gt A39 B Covalent ionic A is more electronegative than B AB bond enthalpy is a combination of the two contributing structures Consequently AB AHAB bond energy is greater than the average of AHAA amp AHBB due to the ionic contribution In the end however Lewis structures are not enough to describe localized bonding in molecules Q Besides Lewis structures what other localized bond theories do we need A VSEPR and Hybridization Q Why do we need to go further than the concept of Lewis A Because there are numerous issues that Lewis structures do not address such as a How is the electron pair bond shared b Which orbitals are involved in the bonding c What geometry should one assign to the molecule bonds angles d Why does sharing electrons lead to stability for a molecule IN LOCALIZED BONDING THEORY WE USE EITHER VSEPR OR HYBRIDIZATION TO ANSWER THESE QUESTIONS wt Madquot bi mylf 3 er PM41 Elvm m 39 HQ 97me e mm by McGranrM 4n AH ughvsmwrvu 2 Hvbridzation Thoerv or Model For this we need the concept of valence state Ex HBeH X Be X X halogen How does one explain the linear shape a Be ls22s2 2s2 is the valence shell If we promote an e39 to the 2p level it is now possible to pair the two unpaired electrons with those of incoming group H or X halide 2s12p1 valence state requires 323 kJmol this doesn t eXplain the shape only how it happens b Hybridization occurs between the s and p orbitals 2s2pZ 2s2pZ OvELAPmC mam wIIH 4 m 3 ff i 39 H 5 M B rH 4343934 mq mm H 45 MW and 5p kybvidu aw I mm 1363 Main Point about Hybrid Orbitals They have a huge lobe pointed in a particular direction that can overlap strongly with an atom along that direction Calculations show that the extent of overlap obtained with the hybrid orbitals of HBeH sp is much greater than it would be with pure s and p orbitals on Be s2 Hybridization t 2 5 sz S J 2 Figure 34 m m mumm m llvvu39 eqmm 1H1 ir39 mm m quothum B ls22s22p1 is the starting standard electron con g B tends to form BX3 if the bonding con guration is ls22s12p2 this allows for three decoupled spins 2s12p2 to form three bonds with H X I 85 Figure 1028 as Sig ma bovch Mm ngJlt in bum w m 5F hyhhds C ls22s22p2 For hybridization ls22s12p3 4 uncoupled spins now we can hybridize these orbitals sp3 hybridization Summary s p Hybridization sp linear molecule sp2 planar triangular molecule sp3 tetrahedral molecule The geometries arise from maximum overlap along these directions sp sp2 and from the algebra of the hybridization for sp3 it also happens to be the maXimum distance from each other in each case CapyHgm a 991 by mam nu mo AH ng msc39vcc Hybridization with s p d orbitals d orbitals become available after the second row dzsp3 dst odnhadmn 56W planaw 3d olsp 4dan fg g nidal mm Five Main Types Geometries are amp coordinate octahedron m coordinate trigonal bipyramidal tbp and square pyramid m coordinate tetrahedral square planar Note that the dXZy2 and dz2 are chosen in particular cases because of standard coordinate labels we assign the X and y aXis to coincide with the ligands l dzsp3 octahedral hybridization dXz yza dzz an pya pz 2 dsp2 square planar hybridization dXZyz 8 px py 3 sd3 tetrahedral hybridization dxy dxz dyz s 4 dsp3 trigonal bipyramidal hybridization dzz 8 px py pz 5 dsp3 square pyramidal hybridization dXZyz 8 px py pz These hybridization schemes help to explain bonding and to correlate structures albeit in a qualitative sense molecular orbital theory is used more commonly now as it is possible to be quantitative LECTURE 1 Goals of the Course 1 To be familiar with the periodic table and how it is organized according to the relationships among the elements 2 To have a rm grasp of fundamental physical principles regarding energy thermodynamics and reaction rates kinetics such that you can use this knowledge to make predictions 3 To accumulate a database of descriptive chemistry of the inorganic elements facts are important 4 Ultimately to achieve a basic understanding through the knowledge of facts of the periodicity of structure bonding and reactivity patterns 39Timlm Br Dis com I o39F39I hL Elemgrrfs 1ure 51 Number of elements 120 Synthetic oq elements 100 Mendeleev39s rst penodn 3 80 1211115 1 Elements known mono 1650 1 Ag Ah Au C Cu Fe I Hg Pb 5 Sb Sn o co 7 I J I 40 f a u39 0 7 3 O 7 1 1 J J 1 1 1a 1700 1750 1800 1850 1950 2000 1900 Yezu disco ercd Copyng 4 1991 b MoGrawHM mm m ngrm nscmzu l 2 I39Mhlsj M MCI39OJS m 534815 EA w gt 1 1 33 45 SB 6quot 7B 213 m 2 Gwyngm ca 1991 by mamwm Inc M Hams aimed r39 Raprhssnmuvu 7 elements g M Rat zuuhi 3A 4A Tmnsniun 1 I l 5 a m metals MUM n C No A a m an in m 73 7887 IE 3 M 5 A 22 3 24 2 25 27 28 29 30 z I a 36 i v Cr Vin Fe Co Ni Cu Zn 53 h r 40 41 4i 4 44 45 as 47 4s 49 5n 4 Zr Nb M0 TC Ru Rh Pd Ag Cd In Squot XE 1 73 74 75 75 77 7x 79 w a 82 83 x4 is as Hf T3 W K2 0 I N All Hg TI Pb i PE Rn NM 103 I05 107 08 I09 Unq 15 um Um Um Une 1 an m V Commonquot a mm m Mauve u hm AH ngm mscvmd 1 A 65 I g l Figuge 826 v v M F A w y L 541 AM l lMQLW a k RA gt0 1 1x 10 W4 x 1049 H 1A 3A 4A 5A 0A A Be 000nm m lt l x may n c N o F N 055 Na Mg A S P S C Ar 11 2 33 an SB 613 73 su m 23 31 2 391 l Cu 5 Ti v Cr u r Co Ni Cu Zn Ga Or A Se m Kr L3 07 06 um 61 Rb Sr Y Zr Nb Mu Tc Ru Rh Pd Ag 01 In Sn Sb Tc 1 x Cs 3 La Hf T w R 05 Ir n Au Hg Tl Pb Bi Pa m RA Fr Rs A Unq Unp Um Uns Una Une Ce Pr Nd Pm Sm En Gd Th Dy Ho Er Tm Vb Lu 11 Pa u Np p Am Cm Bk c a Fm Md No Ly Cnm39nghv amp mm w JcG39m HM m H mm Wm 1 1 53 rmure 85 7 my cum cnhun m V Em muvcunuu u n mum 74 N I In 1 m Mu n 3 n i 39 quot39 3 u 7 s u m H c N o r N a s n lo M x n V n a 39 3 u 5 m 17 m m n 39n vn 1 m n A39 5 397 5 U quot39 z 3 s a e n 5 x U 4 vlt 3n n v lt r Mn Fe N Cu in Ga 6 A Sc m Kr 37 A 5 w u 42 44 M 46 47 49 an 51 2 u 54 Rh Sr v 1 Nb Mn Tc Ru Rh m Ag 1 Sn Sh T l Xc lt2 74 r 7 u w n w w s 1 s xu 6 m x 1 L1 m Tn n Re I n m Hg 11 m m Po M Rn a w m 1m mu m m Hm n Rn A UN Unp Unl Un Una Una m me u mm m mum m 39u rm mm mwcu Au m 1 F Valence arbrh 141 5 la 99 by v k 8 Inc mm 4 953 F GE 3 0512 2 S E c Week 1 Review of Basic Concepts Periodic Table Thermodynamics amp Kinetics Electronic Structure WHAT IS INORGANIC CHEMISTRY Inorganic Chemistry is the chemistry of the elements other than that of C combined with H O N S halogens and the physical properties that these elements and their compounds exhibit Inorganic Chemistry covers a vast area of aqueous as well as non aqueous chemistry Types of inorganic compounds range from ionic solids to gases and molecular compounds Inorganic Chemistry is the chemistry of life as much as it is the chemistry of metallurgy To Name but a few Important Applications Main group elements s p block are important in semiconductor technology eg Ga As Transition elements 1 block are found in trace quantities as the active center of enzymes that catalyze all the reactions in our body and indeed are the catalysts that allow us to produce vast quantities of ne chemicals and polymers from petroleum Rh is one of the most common and is in our catalytic converters in our exhaust systems in our cars The rare earth elements f block lanthanides and actinides many of which are radioactive are important in magnetic materials Classes of Inorganic Substances In the broadest sense the materials that we shall discuss can be grouped into four classifications elements ionic compounds molecular compounds and polymers or network solids The following brief list is presented to show the complicated variety of substances that are encountered in a discussion of inorganic chemistry Greater detail is presented in the appropriate chapters to follow 1 The elements The elements have an impressive variety of structures and properties Thus they can be a Either atomic Ar Kr or molecular H2 02 gases b Molecular solids P4 Sg C60 c Extended molecules or network solids diamond graphite d Solid W Co or liquid Hg Ga metals 2 Ionic Compounds These compounds are always solids at the standard temperature and pressure They include a Simple ionic compounds such as NaCl which are soluble in water or other polar solvents b Ionic oxides that are insoluble in water eg ZrOz and mixed oxides such as spinet MgAle4 the various silicates eg CaMgSi032 and so on c Other binary halides carbides sulfides and similar materials A few examples are AgCl SiC GaAs and EN some of which should be better considered to be network solids d Compounds containing polyatomic socalled complex ions such as SiF6239 CoNH363 FeCN6439 and NiH2062 3 Molecular compounds These compounds may be solids liquids or gases and include for example a Simple binary compounds such as PF3 SOZ OsO4 and UF6 b Complex metalcontaining compounds such as PtC12PMe32 and c Organometallic compounds that characteristically have metaltocarbon bonds Some examples are NiCO4 Zf CH2C6H54 and UC8H82 4 Network solids or polymers Examples of these substances discussed in Chapter 32 include the numerous and varied inorganic polymers and superconductors One example of the latter has the formula YBazCu307 Classes of Inorganic Structures Organic is mostly based on the tetrahedral geometry Why Carbon requires 4 electrons to complete its valence and a tetrahedron is the best way to arrange four groups around a central atom Wo lone pairs with s and p orbitals Inorganic chemistry is much more complicated tetrahedron cube For example The ve Platomc sollds octahedron form the bas1s for many inorganic dodecahedron structures Icosahedron Less regular polyhedra Trigonal bipyramid Trigonal prism Square prism And Other planar structures Chains Square planes Triangles Are also known for inorganic structures 39gt Quite diverse Classes of Inorganic Reactions Cotton book cites 12 different ones 1 Acid base According to the definition of BronstedLowry the neutralization of a proton donor by a proton acceptor According to the definition of Lewis the formation of an adduct between an electronpair donor and an electronpair acceptor A lesser known definition is that of Lux Flood namely the reaction of an oxide ion acceptor with an oxide 2 Addition A reaction in which a group molecule or ion combines with another Common examples are additions across a multiple bond and addition to an atom that is able to undergo coordination sphere expansion an increase in occupancy This reaction is the converse of elimination 3 Elimination A reaction in which a group molecule or ion is separated from another Examples are dehydrohalogenations and eliminations from metal centers that are able to undergo coordination number reduction a decrease in occupancy This is the converse of an addition reaction Redox a reaction in which an atom ion or molecule gains reduction or loses oxidation an electron or electrons Insertion The interposition of a new molecule group or ion between atoms in a structure such that the added molecule group or ion separates the two parts of the structure that were formerly bound together Substitution Displacement The exchange of one atom molecule or ion for another in a compound Rearrangement Isomerization A conversion of one isomer into another cistrans for example Metathesis Exchange An exchange of comparable groups such that two compounds form two new ones AXBY9AYBX Solvolysis A reaction with solvent when the solvent is water it is called hydrolysis 10 Chelation A reaction in which a group typically called a ligand is able to bond to a central metal ion simultaneously through more than one donor atom 11 Cyclization A reaction that leads to the formation of a ring 12 Nuclear reaction A reaction that changes the atomic number or mass number of an atom 339 Chapter 8 Back to Basics The Periodic Table and the Chemistry of the Elements Q How does one organize facts in the area we call inorganic chemistry A Not as easy as for organic compounds We are dealing with many more compounds and elements Best way is the Periodic Table Earlier in the course we discussed the theoretical basis for various periodic trends Now let us turn to a chemical basis Part A Types of Elements Part B Chemistry of the Elements in Relation to their position in the Periodic Table Part A Monoatomic Elements He Ne Ar Kr Xe Rn Filled shell Diatomic elements H2 N2 Oz F2 C12 Brz 12 ns2 np5 elements can complete their octet by making bonds Polyatomic Elements P4 Sn Seg Fullerenes C60 C70 etc After the first row elements the diatomics become unstable due to decreased p7Ip7t bonding NEN and 020 for example have extensive 71 bonding eg makes siX PP bonds to P White Phosphorus is I tetrahedral P P P be stable P has three allotropes white black and red Sulfur has numerous allotropes that involve tings ss 11p to 20 8 S 342 Sg orthorhombic sulfur s szzoseix Ls s 3m7 5439 Dmedra ang e 98 9 W a Figure 81 l39hc m ume or ox thl39hnmbiC sulhu w 1hr Ljv39LllL39 51 Halt culr In Sucking ml lnhlk39n39lllIW In 1h sulitl 343 344 Extended Structures for Elements Chains Twodimensional layers Three dimensional networks Most C P S common elements Si AS Se that form extended Ge Sb Te phases Sn Bi Carbon graphite is twodimensional diamond is threedimensional fullerenes are molecular Boron forms structures based on B12 icosahedra 345 CLbOH Figure 83 Hn39 mum mm mn H1 wwhm Figure 82 The diamond slruruu39c SL CII mm two points oi39 ew u The mmm Lional unit cell If A i tacked has lzrwm run prrpvmln w lar D he body dia Inndh of Hit ubc Rmmmhm howuvcr that mix Ls mu a Iaym ll39l Lure in properlim arc the sanu39 in all dircrlinm F E y 346 C New 32 quotW wfluddomm wMYf v 0 0 c shnet Zohexa 5 MM oz 1 l2 P011 3005 k 3 m W g i v 4 h 9 es 9 erbau 9 Figure 84 I Iw w uuul39cs nt sunw urlhc small fl Il 39rsnm 2H n 1 i u t m mems ul 391 Reprimml mh PL39I39IHiVSiUII from 1 D rderich and K L thunn quotBm39nml rim 39Hn Hmlm Fullen39nrsquot Arr Slum l 13939 25 19426 992 Iopvright 1992 Amerwan Zhumu39ul may Buckminster Fullerenes Bucky balls Named after F Buckminster Fuller ArchitectEngineer 0f geodesic domes 347 Boron Three allotropes all of which are based on the B12 structural unit B12 icosahedral building block 0t boron cubicclosepacked B12 spheres with weak links 3 boron complicated Tetragonal boron B12 units with BB bonds gtkmost stable lt between them 348 Silicon and Germanium Si and Ge diamond structure Tin Sn diamond structure but it displays an interesting equilibrium Diamond structure but it displays an interesting equilibrium 18 C XSfl BSn CCGray99 CCWhit699 Diamond Distorted Structure close packing d575 gcm3 higher density d7 31 gcm3 349 Metals Most of the elements in the periodic table are metals Physical properties 1 High re ectivity 2 High electrical conductance 3 High thermal conductance 4 Mechanical Properties such as strength and ductility Three main structural types for metals 1 Cubic Closest packed ccp 2 Hexagonal closet packed hcp 3 Bodycentered cubic bc 350 12 nearest neighbors r 8 nearest neighbors Distribution of cop hep be in the periodic table Most deviate from the ideal structure Figure 87 The occurrcnn ul hexagonal clustpztrkt tl hcp r39nlnv loswpm knl CCP and hod riccntcretl t llll39 In H structures among the elements Vlicrt two or more symbols are used lll hirgt st I39t lit39t39scnls tho Stillth form at 3 1 Thu i39 ll in beled ltrpccp signi es t mixed i lifll rllillf V type ul39clusu parking with over all hexagonal symmetry l l1lplfl with permission lrmn ll Krebs lrmulsugz39 lim Anorgzmisu39n Krixtallrlmnir 2 linkt39 39Lrlug 968 351 Bonding in Metals Coordination number is high 8 or 12 Properties are very distinctive from other elements These two points hint that bonding in metals cannot be similar to that found in normal molecules No ionic contribution is possible Two electron covalent bonds between all nearest neighbors is impossible Q What is going on A To answer this imagine bringing an array of atoms from an in nite distance apart to close interactions gtAtoms touch amp orbitals overlap so many atoms are involved such that the M 0 Diagram of such a growing array becomes essentially continuous Energy 3p 35 Vim310w 39chm 23 Moi WWW Mal x oondi quotMgg f a V90 a g w r0 r gt 352 Figure 88 Energy bands of sodium as a func tion of internuclear distance The actual equilib rium distance is represented by 7 0 353 A continuum of energy bands spreads over the entire metal gt the electrons are delocalized The overlapping atomic orbitals form closelv spaced orbitals in the metal called m Bands can be lled or empty The lled ones are equiv to HOMO s Highest Occupied Molecular Orbitals The empty ones are equiv to LWO S Lowest Unoccupied Molecular Orbitals gt No of electrons gt No of electrons 370 Hard and Soft Acids and Bases 1965 Ralph Pearson introduced the hardsoft acidbase HSAB principle Hard acids prefer to coordinate the hard bases and soft acids to soft bases This very simple concept was used by Pearson to rationalize a variety of chemical information 1983 the qualitative definition of HSAB was converted to a quantitative one by using the idea of polarizability A less polarizable atom or ion is hard and a more easily polarized atom or ion is soft 371 The Quantitative Definition of hardness IN LP EA 2 I The average of ionization potential and electron af nity Actually the electronegativity X of a neutral species 15 the same IX LP EA 2 l One can relate n hardness to the gap between the HOMO and LUMO E ener I 271 ELUMo EHOMO I gY HOMO and LUMO orbitals molecules or simply highest occupied and lowest unoccupied orbitals in atoms participate in the bonding more than any other levels The lower the energy of the HOMO and the higher the energy of the LUMO the more stable the species is thermodynamically The greater the n value the more hard the species is 372 Basically HSAB theory endeavors to help one decide if AB CD AC BD goes to the left or the right also helps you to know if AB CD forms AC BD or AD BC Hard and Soft Acids and Bases Hard acid High positive charge Small size Not easily polarizable Hard base Low polarizability High electronegativity Not easily oxidized Soft acid Low positive charge Large size easily oxidized Highly polarizable Soft base High polarizability Diffuse donor orbital Low electronegativity Easily oxidized 373 Hard acids prefer to bind to hard bases and soft acids prefer to bind to soft bases This statement is neither an explanation or a theory It is simply a guideline that helps one to qualitatively predict the relative stability of acidbase adducts Lewis acids A Lewis bases B or B39 A the smaller and more highly charged the harder it Will be B or B39 the larger the atom or ion the softer it will be Classification of hard and soft acids Listings of hard and soft acids and bases are the result of obserVing the preferences for reactions to go to the right or left 374 Example a given base B may be classi ed as hard or soft based on the equilibrium BH CH3Hg CH3HgB H Hard Acid Soft Acid There is a competition here between the acid H and CH3Hg If B is soft then gt to the right If B is hard then lt to the left Important to remember that the listings in the tables do not have a sharp dividing line between them These terms hard amp soft are relative Some are borderline and even though Within the same category are not all of the same degree of hardness and softness 375 e g although all alkali metals in ionic form M are hard the larger more polarizable Cs ion is much softer than Li also N compounds are not all equal H3N versus I N pyridine is much more polarizable more examples common PR3 SR2 are soft bases soft Hg2 Pd2 Pt2 are soft acids spec1es COmmOn NH3 ROH H20 are hard bases hafd Ti4 Si Co3 are hard acids spec1es RS39 versus RO39 Hg SR H Hg2 HSR does this reaction proceed to the left or right Hg OR H Hg2 HOR left or right Tllgla 78 Cll l cauon a fun Ind soft colds Hazd 5cm H Li Na39 KquotRb Cs39 Be EXCEL Ms C11 Sr 38 Sen uquot Cc Gdu Lun 11 U uo39u Pu 11 Zr pr39 you an cry M ogl wqu39 nu Mnquot Fe Co BF Eds HOE Mquot AlCH AICJa MHn GKquot 1quot CO 00 NC39 Siquot Sn CHSnquot camsrx Nquot RPOR ROPOI Asquot 39 a gallbonding molecules Batchline adds 0 Np Dumb x m 1 Rm 0 3581 GBH RICquot CsHs Sn Pb NO Sbquot Bi 50 Salt adrk Chma Pdn mu mu 11 AE Au39 Cd HF H8 CHJ IS H GMCHQa GBCI GaBr Gala 11 11CH 11mbenes 4 aacnpton trinitrobenune chloroani quinanes tetracyanoclhylene rm 0 RO RS RSe Tc RTE a Br 1 139 ICN are CL Br I N 110 R0 4 metal atom and bulk man T bla 77 Classification of hard and soft bases Hard Bases NH RNH3 N2H4 H20 OH39 Oquot ROH RO R10 C 300039 C0quot NOa POF 804quot C10 F 0 Borderline bases CsHsNHz CsHsN Ns N2 N01 SOquot2 Brquot Su bases Rquot CgHL CsHa CN39 RNC C0 SCN RaPy ROMP RsAS R23 RSH RS 320quot I Ti4lSR39 H Ti HSR left or right Remember it is all relative Ti4lOR39 HSR39 Ti SR39 HOR39 Predict which way the following reactions will go HlNaF HF Nal R A113 3NaF AlF3 3Nal R CaS H20 CaO HZS R TiF4 2Tilz TiI4 2TiF2 L Con HgBrz CoBrz Hng L HgO st HgS H20 R How about the following 1 srs2 2HzO gt sro2 2st 2 sro2 2st gt srs2 2HZO 3 Cuzs H20 gt CuzO st 4 CuzO st gt Cuzs H20 Which ones will proceed as written R 1 sf hard 3239 soft 0239 hard H hard L 2 sf hard 0239 hard L 3 Cu soft 3239 soft 0239 hard R 4 Cu soft 3239 soft 0239 hard 1 and 4 will proceed as written 398 Chapter 10 Group IA 1 Alkali Metals Lithium Sodium Potassium Rubidium and Cesium Similar to H in that they form M other cations that are related are NH4 like K and T1 Rb Q 5 Na and K are very important physiologically Cells differentiate between them by speci c complexation reactions L1 salts are used to treat man1c depress1Ve disorders KNO339 is used in fertilizers Na as NaOH NazCO3 NaZSO4 are among the top 50 chemicals in terms of production 399 What Dictates the Chemistry of Alkali Metals Low ionization energies to make l cations M ions are spherical and hard low polarizability High 211d ionization energies prevent the 2 oxidation state Most bonding interactions are ionic due to low polarizability Li is strongest in terms of polarizing ability due to sizecharge ratio in other words it forms the most covalent compounds Li is least reactive Cs is most reactive Preparation of alkali metals is mainly by electrolysis of fused salts Electrolysis NaClS Nas C12g 400 Reactivity Comparisons Lis H20 510W LiOH 12 H2 25 C Nas Hzo gcfg NaOH 12 H2 ames KSHO KOH1H 0 2 25 C 2 2 Rbs Of CSS Hzog lgg m39 12 H2 slow 25 0C 6Li N2 2Li3N rubyred crystals unique among the alkali metals 401 A Fundamental Difference Can Be Observed in Q Reactions main products in hold 1 Li 02 gt LizO trace Li202 2 m Oz gt Na202 7 you get NaOz ifyou force it 3 K Rb or Cs 02 gt Mo2 M20 M202 2 oxide peroxide superoxide 0239 0 0 02239 0239 Q Why differences A The differences in reactivity with Oz can be attributed to cation size Solutions of Alkali Metals in Ammonia NH3e Nas finely divided Na in NH3 solution N e dilute solutions 402 Q What do these equilibria mean A That the NH3 medium is able to solvate an electron The solvated electron occupies a cavity in the NH3 Where it is somewhat delocalized over a large volume so that the surrounding molecules are polarized The polarized NH3 molecules form the cavity due to NH3 lone pair e39 repulsions Na NH3e Na e39 is stable Without air or water but eventually can react further to give NaNHz sodium amide 12 Hz This reaction is facilitated by photochemical and catalytic routes 403 Binary Compounds only two elements OdeCS M20 M202 M02 hydroxides MOH not really binary but these are Viewed as metal oxides as well salts MX X halide for example Oxides Peroxides and Superoxides of Alkali Metals are Easily Hydrolyzed MD H20 2M 2 OH M202 2H20 2M 2 OH H202 2M02 2H20 02 2M 20H39 H202 Hydroxides NaOH etc White yery hygroscopic deliquescent solids means they literally dissolve in the moisture om the air solids also absorb C02 from the atmosphere solutions do as well 404 Salts MX X39 many types of anions most give colorless crystalline ionic compounds Anomalies arise with lithium compounds Why Mainly due to its small size and its effect on lattice energies com are l LiH stable to 900 0C NaH decomposes at 350 0C 2 Li3N stable Na3N does not eXist at 25 0C 3 LiOH T Li20 ie it decomposes MOHS T MOHg ie they sublime 4 LiOH is much less stable than the other MOH compounds 5 Li2C03 LiZO C02 thermally unstable carbonate not so much for others 6 LiF is not very soluble more covalent LiCl is soluble in pyridine unlike NaCl which is very soluble in water Solvation of Mialkali metal ions issues coordination sphere How many waters are directly bound to M total coordination sphere How many total water molecules e g 0H2 LiH204 is considered the first coordination sphere L quotquotIIIOH2 found in the solid state H2O 0H2 LiH204 21 H20 additional water in the solvation shell In other words Li in H20 exerts an in uence on 25 H20 molecules 406 Lii Mi Ki Rbi gt Ionic RadiigA 090 116 152 166 181 Approximate Hydrated 340 276 232 228 228 Radii gAg Approximate Hydration 253 166 105 100 99 Numbers g of Hzo Hydration Enthalpies 519 406 322 293 264 ngmolz Note that Li the smallest ion exerts the most in uence on water gt it has the highest total hydration number Q Why A greater charge density 407 As a consequence Lil with its 25 hydration sphere H20 molecules will not associate with anions in ionexchange resins very well Complexation of Cations by Crown Ethers and Cgptates M alkali metals are not easily dissolved in their salts into nonaqueous solvents They need polar usually H20 molecules to stabilize them in their solvated forms To circumvent this chemists have used the two types of molecules shown below pm b m Lu govy 18crown6 222crypt 408 crown ethers cyclic ethers the number of O atoms and the O 0 total number of atoms in the ring 3 are speci ed in the name 0 O L J 18crown6 O O dichlohexyl 18crown6 Binding is largely electrostatic in the caVity of the cyclic ether Important to have a close size match of the caVity and the ion if you want binding to be tight 18crown6 Li lt Nat Cs lt Rb lt K Binding Best size is less match 409 C tates L W More potent and selective agents for binding alkali cations and others Both N 4 and O atoms are present ONd f they are polycyclic which 0 V 3 means they can Jlly surround a cation Rb222crypt These are very important reagents in organometallic chemistry for getting salts to dissolve in nonpolar or low polarity solvents K 7 O 1 x ti 1 n gt n l Bumsmud 1 Am Chem Sat 96 7203 7203 1974 Copynghl 0 I974 rmcrilt an Zhemiral Samy 410 Biological systems use a similar strategy for transporting alkali metals Nature uses cyclic peptides like the ones shown below to transport M across membranes For example 0 0 0 Mo N 0 gi valinomycin m nonactin Figure 103 The sll 1er oflhc nunm39nu Comple 0 K Reproduced by permission rmm n A Fcnmn am 5m Rm 977 6 S25343J Alkali Metal Organometallics 2Li RC1 gt LiCl39 R39Li organolithium reagent LiR39 R Me Bu etc are used to deliver R39 groups in reactions They react very swiftly with Oz H20 and are pyrophoric which means that they burn in air Other Common Compounds Often Used In Organometallic Chemistry Alcohols amines and other XH bonds are highly reactive towards the neutral alkali metals M Alkoxides MOR39 MROH gtMOR 1sz Same type ofreaction as Ll HZQ gt LlOH 12 H2 Amides M NRZH gt MNR239 from amines M NRH2 gt MNRH39 M NH3 gt M NH239 What is happening here Redox chemistry of course M is oxidized H is reduced 412 NnNHR Na39 am o nml RNHZ H o NH 2 N I 07 H20 H20 e NaCl r M Na NnOH H20 H2 ROH H2 NEH MCI NaOR NaC C222 M I Rb Cs NacmrNa LiOH CHaLi 20 A CH3 LINHR m RNH2 Lizo LiR H2 02 Li amp L1H LiCl I ROH NZ LiJN 413 Chapter 11 Group 11A 2 Elements Alkaline Earth Elements Beryllium Magnesium Calcium Strontium Barium Radium Be important element in a negative sense very toxic if its compounds are inhaled destroys lungs minor element in terms of technical importance Mg Ca Sr Ba are in many common minerals and in the ocean e g limestone which is CaCO3 dolomite which is CaCO3 MgCO3 Ra all isotopes of this element are radioactive Group IA Alkali Metals larger atomic radii lower melting and boiling point lower densities lower ionization energies lower hydration energies lower lattice energies gt gt gt gt gt 414 Grou 11A Alkaline Earth Metals smaller atomic radii increased effective nuclear charge higher melting and boiling point higher densities higher ionization energies higher hydration energies higher lattice energies Chemist of Group HA some highlights E very small ionic radius g 031 A compared to Lil is 060 A Nal is 096 A Kl is 133 A Mg2 is 065 A Ca2 is 099 A etc Due to the very small size of Be2 it cannot eXist as a simple cation in its compounds Consequently even Ber and BeO are more covalent than they are ionic unlike other MN species F Be F linear quot quot coordinatively unsaturated eXists only in the gas phase 416 Polymerization of BeXz compounds is common BeF2n BeC12n etc 2 C14 C1 C1 C1 Be Be Be B6 C1 C1 C1 C1 C1 C1 a portion of BeClzn is above Since BeXz compounds are so coordinatively unsaturated they are useful as Lewis acids in many reactions Ber 2F39 gt BeF4239 BBCIZ 2 R20 gt BeC12OR22 ether assumes tetrahedral coordination Chemistry 462 Goals for Chapter 23 Introduction to the Transition Elements Ligand Field Theory Know the basic properties of the dblock or transition metals and transition metal complexes Understand the three main bonding theories for transition metal complexes Crystal Field Theory CFT Ligand Field Theory LFT Molecular Orbital Theory MO and the relationships among the three Understand that depending on the types of orbitals symmetry that the ligands have available to overlap with the d orbitals of a transition metal the d orbital splitting will be different Know that the most important Molecular Orbitals in the transition metal ML6 compounds are the d orbitals which are filled last In an octahedral molecule the d orbitals split into two groups the tgg set dXZ dyz dxy which is lower in energy than the eg set dX2y2 dZZ Know that the d orbital splitting in a tetrahedral geometry ML4 leads to two different sets of d orbitals whose energies are the reverse of the octahedral geometry In a tetrahedral geometry the e set dX2y2 dzz is the lowest and the t2 set dxz dyz dxy is the higher energy set Know that the splitting energy between the tgg and eg sets is called the octahedral splitting energy and the common symbols are A0 and 10Dq we did not use the latter The t2g and eg orbitals in IL6 represent the Highest Occupied Molecular Orbitals HOMO s and the Lowest Unoccupied Molecular Orbitals LUMO s In tetrahedral the e and t2 levels are the HOMOLUMO set Know that TEdOl lOIS have a low energy filled osymmetry group orbitals and b higher energy filled n symmetry group orbitals that can overlap with metal orbitals that have the same symmetry recall the possible metal orbitals are the nine valence orbitals dfive sone and pthree whose energies are in that order The overlap leads to the t2g and eg sets of d orbitals with a very small splitting energy A0 value Know that odonors have only low energy osymmetry group orbitals with which to participate in bonding to the metal which has d s and p orbitals whose energies are in that order Their interaction with the d orbitals leads to an intermediate A0 value Know that nacceptors have a low energy filled osymmetry group orbitals and b very high energy empty 1tsymmetry group orbitals that can overlap with metal orbitals that have the same symmetry These ligands produce the largest A0 value Know that the tetrahedral molecules produce MO energy diagrams similar to the octahedral ones but that e lt t2 in energy and that overall the A is much smaller than A9 for the same metal and ligands A is 4 9A9 Know that Crystal Field Theory CFT arrives at the same d orbital splitting energies found in MO theory by assuming that the metal and the ligands are point charges This is a purely electrostatic bonding theory The positively charged metal ion without ligands free ion has all five d orbitals at the same energy When point charges considered to be negative charges of Ligand electrons are brought around the metal the orbitals split into two rou s tgg orbitals go down in energy by 25A9 due to less repulsion of M electrons with L electrons and eg orbitals go up by 35AQ in energy Know that Ligand Field Theory LFT is an extension of the concept of Crystal Field Theory but it allows for covalency considerations in the M L bonds Know that HighSpin HS or LowSpin LS Complex refers to the filling of the tzgeg and et2 sets with electrons The Octahedral molecules can be either HS or LS but tetrahedral is only HS Know that the relative amount of the A0 and At values can be used to explain whether a molecule is a HighSpin HS or a LowSpin LS Complex The choice of whether to be LS or HS depends on the overall LFSE Ligand Field Stabilization Energy for the two different electron configurations LS versus HS One can calculate the LFSE for dld10 configurations by assigning the energy of 25Ao for every electron in the tgg set and 35AO for every electron in the eg set If there are pairs of electrons add a Pe term for every LP Know that CFT for the tetrahedral geometry predicts the opposite sets of orbitals will be repelled and stabilized by the application of a tetrahedral crystal field The e set dX2y2 dzz is the lowest set and the t2 set dxz dyz dxy is the highest Know that the square planar d orbital splitting can be derived from the octahedral energy diagrams by considering the effect of pulling two ligands away along the z direction This serves to stabilize all orbitals with z character and destabilize any orbitals with pure X and y character The limit of pulling away the two ligands is to make an ML4 square planar compound Know the diagram that applies to this and that SQUARE PLANAR MOLECULES ARE NEVER HIGH SPIN Know how to sketch the possible dld10 electronic configurations for an ML6 octahedral and ML4 tetrahedral compleX and tell the possible HSLS configurations whenever applicable Be able to tell how many unpaired electrons are possible for each type of dn configuration and HSLS combination Know that CFTLFT can help one to predict properties of transition metal complexes most importantly for this chapter magnetism number of unpaired electrons and electronic spectroscopy qualitative determination of how many transitions and whether they will be easy to observe or not 380 Hydrogen It s compounds and Selected Uses Hydrogen is a very important element Not only does it combine with carbon to give numerous organic compounds but also serves as a fuel and as a reducing agent for both metaloxides and nonmetals Hydrogen forms more compounds than any other element including carbon Some Physical Properties Hydrogen is the lightest element It boils at 2258 C The bond dissociation energy HH gt H H is 1044 kcalmole The molecule is thus very thermally stable At a temperature of 1727 C only 1 of H2 molecules in a sample of the gas will be dissociated to atoms Isotopes of Hydrogen Hydrogen has three isotopes hydrogen 1H deuterium 2H or D and tritium 3H or T Deuterium a natural isotope of hydrogen sometimes labeled D has one neutron in addition to the one electron and one proton present in normal hydrogen 381 It is present in seawater for example as D20 or HDO the ratio of DH being 15000 The other isotope of hydrogen tritium is sometimes depicted as T It has two neutrons in addition to the one electron and one proton Tritium is radioactive and does not eXist in nature The diatomics that are possible are H2 D2 T2 HD HT DT The two hydrogen isotopes play a very important role in nuclear fusion reactions which release a very large amount of energy which if harnessed can replace conventional fuels In nuclear reactions the energy released is given per atom rather than per mole as in chemical reactions One evatom is equal to 2306 kcalmole The fusion reaction between D and T is the basis for the hydrogen bomb It produces 4He and a neutron along with the 176 Mev of energy This weapon requires the use of an atomic bomb fission reaction as a detonator to establish momentary temperatures of up to one million degrees to get the fusion reaction going Presently attempts are being made to fuse two deuterium atoms obtained from seawater to yield 382 useful energy It is doubtful that such energy will become available for everyday use in this century but the available fuel supplies of oil and coal can be expected to be exhausted sometime in the future if other energy substitutes are not found Note that the population of this Earth was 24 billion in 1944 and is presently gt5 billion The necessity for alternate sources of energy is thus obvious The possibility for obtaining energy from fusion reactions appears to be good even though it may turn out to be eXpensive It should be realized that if it can be harnessed by fusion the energy contained in one cubic kilometer of seawater is equivalent to the world s total supply of petroleum Preparation of Hydrogen Hydrogen is eXpensive to prepare It is prepared by electrolysis of water a process that requires the use of eXpensive electricity Research has been going on for many years to develop methods of obtaining hydrogen by the splitting of water using light energy but the long term practicality of this procedure has yet to be established 383 Electrolysis For electrolysis to occur an electrolyte ie ions must be present in the water Sulfuric acid can be used for this purpose Illustrative reactions are shown below 1 Electrolysis of Water H2804 2 H20 2 H2 02 electrolys1s The half reactions are reduction cathode 4 H 4e39 gt 2 H2 oxidation anode 2 H20 gt 02 4 H 4e39 2 Electrolysis of Brine an aqueous NaCl Solution electrolysis 2Nazcy2HZQ 2Na20H39H2C12 Sodium metal is not deposited from aqueous solution hydrogen is evolved instead 3 Steam Reforming of Hydrocarbons an2 n H20 Nl catalsLtgt 11 C0 2n1 H2 600 C The CO thus produced can be further converted to hydrogen by the watergas shift reaction catalyst 11 CO H 11 CO 11 H20 250 0C 2 2 384 The COzHz product is bubbled through water leaving hydrogen behind The C02 is soluble in H20 Any untreated CO cannot be allowed to escape in the atmosphere as it is very toxic so the watergas shift reaction must be made to go to completion The hydrocarbons used for steam reforming are CH4 methane and C2H6 ethane Reactions of Hydrogen Some important reactions that involve hydrogen and illustrate its reactivity are 1 Preparation of HBr catalyst H2 Brz W 2 HBT g 2 Preparation of Ammonia Haber Process N2 3 H2 Fe catalyst 2 NH3 pressure The conversion of N2 per pass is only 17 The unreacted gases are recirculated It is noteworthy that the conversion per pass was 15 when this process was 385 rst invented in 1915 Evidently not much has changed since then Ammonia and ammonium salts are used in fertilizer 3 Formation of Hydrides 2 LilH39 H2 2 Li 700 C LiH is a White crystalline solid that melts at 680 C 4 Isolation of Pure Metals from Ores by Reduction a CuZS 2 02 gt 2 CuO so2 M082 02 gt M003 2 802 C C110 H2 gt C11 H2O M003 3 H2 gt MO 3 H2O Molybdenum Mo is used in special steels Where strength and corrosion resistance are required 5 Hydrogenation Reactions 386 l RHCCHR H2 gt RCHzCHzR saturated hydrocarbons The hydrogenation of double bonds which occur in vegetable oils yields solid fats ie Crisco catalyst Co Mo oils 2 Coal H2 6 C0 H2 Synthesis Reactions Synthesis gas which is a mixture of CO and H2 is obtained from coal and can be converted to organic compounds Exemplary reactions are Cu Zn catalyst C0 2 H2 T CH3OH methanol Methanol added to gasoline increases its octane value 7 FischerTropsch FT Synthesis 1 CO H2 Mlxture of hydrocarbons Catalysts Co Fe Mo 387 This process was used by Germany during World War II to manufacture gasoline from coal Compounds of Hydrogen that contain one other element compounds with only two element types are called Binary Compounds l Ionic or saltlike hydrides NaH39 contains the hydride ion H39 2 Molecular or Covalent hydrides SbH3 SiH4 H20 NH3 3 Interstitial Hydrides Interstitial hydrides are compounds prepared by absorption of H2 into transition element metals or alloys The hydrogen is usually present in the atomic form as H2 These hydrides can be used for the storage of hydrogen fuel storage because the H2 can be easily liberated by heat Typical examples are TiH17 and LaNi5H6 It turns out that more hydrogen can be stored in such hydrides on a volume basis than by liquefying hydrogen Bonding features of Hydrogen 1 Numerous MXHy hydride materials are known that are often nonstoichiometric 2 Formation of 3center bonds Via Hbridges CO CO CO CO H2 xHx s I I B 39 OC Cr H Cr CO ocl oc H H H co co 3 The Hydrogen Bond polar bond 839 8 X H 7777777777 electronegative Hbond Largely Electrostatic between Y and H Bottom Line Main chemistry is loss of an electron to give Hl and gain of an electron to give H39 389 b Water of Crystallization Hydrates In some compounds water is an integral part of the crystalline material as indicated below 34 OC NaZSO4 lO H20 NaZSO4 10 H20 This reversible adsorption accounts for the desiccant dehydrating action of anhydrous sodium sulfate The interaction between water and the Na or SO4239 ion within the crystal is weak thus water evolution can occur at a low temperature c Coordinate Covalent Bonding Water can form coordinate covalent bonds in a number of metal salts such as CuSO4 5HZO Anhydrous copper sulfate is white but the penthydrate is blue due to the coordination of water molecules about the copper atom In CuSo4 5H20 four water molecules are bonded with the water coordinated onto the cupric ion It is thus properly formulated as CuH204SO4 H20 Copper sulfate pentahydrate becomes anhydrous loses all its water at temperatures obove 250 C as opposed to 34 0C above more difficult to release H20 coordinated to a metal 390 The acidic behavior in water solutions of some metal salts can be explained by the strong coordination of water to the metal atom For example aluminum nitrate hexadrate A1NO336H20 is best represented by the formula AlHZO6NO33 The siX water molecules form siX strong AlO bonds The acidic behavior of this compound results from the hydrolysis of the hydrated aluminum ion Hydrolysis A1HZO63 gt AlH206OHl3 H etc 391 Ice I Tetrahedral O atom arrangements Hydrogen Bonding in Ice There are nine known crystal structures of ice Figure 94 Flu a 7v mwn Hw ONO rhwmvm 77 OO distances are 275A Water is a most abundant and interesting compound This supplement to the notes emphasizes some of is important properties Bonding Aspects Because of the electronegativity difference between hydrogen and oxygen the 0H bonds in water are highly polar The 5 in the diagram below indicates a partial charge 5 O 5 5 HQH 105 C The HOH angle is 105 We can think of water as having two lone pairs of electrons on the oxygen atom The resulting repulsion between these electron pairs and the two OH bond electron pairs would then cause the HOH angle to be less than tetrahedral 1095quot Hydrogen Bonding Several of the properties of water can be attributed to its ability to form extensive hydrogen bonding in the solid and liquid phases Only the gaseous phase can eXist as discrete molecules In the solid and liquid phases aggregates are held together in the threedimensional network by 177A Hydrogen bonds are weak in comparison to normal covalent bonds 834 ldmole and vary in strength from molecule to molecule The Hbond in water is 21 kJmole and is directional that is it is usually between a lone pair of electrons on an atom of one molecule and the positive pole of another molecule Hydrogen Bonding plays a vital role in biological processes especially in holding protein structures intact and it is responsible for the high boiling point of water We can obtain the boiling point of water as a function of molecular weight in the absence of hydrogen bonding from a plot of the boiling points of its congeners HZS HZSe and H2T639 quotm m quot my a 2m 5 I ma cm Appropriatedatafornmhaplo v Campnnm 3 mg 15 H20 100 34 gs 75M HZSe 741 a mm mm a The boiling points of H28 HZSe and H2Te increase with increasing molecular weight but the bp of water is some 200 C higher than that expected 90 C by extrapolation Hydrogen bonding is almost negligible in HZS HZSe and H2Te mostly because of the large size of the central atom Hydrogen Bonding in water gives it veg special properties 1 Very high boiling point 2 VERY LOW DENSITY OF SOLID FORM ICE 3 Glue for proteins and DNA H 0 Hydrogen Bond H N 20 Kcalmol c3 r r H H O 39 Covalent Bond N 450 Kcalmol H 395 Bottom Line LIFE AS WE KNOW IT WOULD NOT EXIST WITHOUT HYDROGEN BONDING WHY H20 would be a gas at room temperature we would not be here H20 solid ice would not oat lakes would freeze from the bottom up and aquatic life would not be capable of existing WaterContaining Compounds Water is known to form hydrates and compounds called clathrates with various elements a Clathrate Compounds Clathrates are cagelike compounds of water in which other molecules or atoms can be trapped For example Xenon forms compounds 396 of the composition Xe7 3 H20 and chlorine C12 8HZO Water in the solid state forms pockets or cagelike holes Where the Xe atoms and C12 molecules t Hydrocarbons like methane CH4 and butane C4H10 also form clathrate compounds with water It is presently believed that xenon and chloroform CHC13 act as anesthetics by forming clathrate compounds with water Within connecting parts of the nervous system thus clocking the transmission of pain It is also believed that methane gas is trapped under the sea by forming clathrate compounds with water My LMIHq 32 H Alma NaH L39H Cu L R N w m u 1quot catalyst mum H Canaan W H2 Acoz O4co candy Cuo N2 woJ Fem cu N w 39 E 6 Flgura M Sum rzacuons or hydrogen Lecture 2 Review of Basic Concepts Thermochemistry Enthalpy H heat content H Changes With all physical and chemical changes AHO Standard enthalpy 250C 1 atm HO for all elements in their standard forms by de nition Exotherrnic vs Endotherrnic AH lt 0 AH gt 0 Heat is released Heat is absorbed Because AH H products H reactants Many special Enthalpy changes fusion melting s gt 1 vaporization l gt g sublimation s gt g ionization loss of an e39 or electrons electron af nities capture of an e39 or electrons AH look at signs and rationalize e g EXO Clg e39 gt Clg AH 349 kJmol EXO Og e39 gt O39g AHO l42 kJmol ENDO O39g e39 gt 021g AHO 844 kJmol Bond Energies Simple case HFg Hg Na AH 566 kJmol ENDOTHERMIC The enthalpy of this process is the HF Bond energy the energy released when the HF bond is formed Not so simple case HZNNHZ 2Ng 4Hg AH 1724 kJmol T NOTE This is not the bond energy for any of the bonds It is a total enthalpy change Need to Estimate If we know that NH3g Me 3Hg AH 1172 kJmol 117 2 391 kJmol Then ENH 3 Ifwe assume this number is valid to use for Hydrazine the formula of which is HZNNHZ or N2H4 Then ENN 1 4ENH ENN 160 kJmol we have to live with these estimates Thermochemical data can be tabulated by this method 12 Chamerl ScmePrehmmnlies Kablell sumNW mm nmllmmll m U H anjmnl 1 u lu th homlmumm rixmh K v m in n Use these values to calculate the energy that it would take to form a molecule Entropy and Free Energy Two factors in chemical reactions 1 Enthalpy H 0 Energy heat dissipated 2 Entropy S kmiol State of organization order versus disorder which is a statistical probability When AH is more negative exothermic and AS is more positive rnore disordered a reaction is more favored AG Free energy which is in 01 Involves the relationship between AH AS AG AH TAS T in degrees K Example CHZCIZ Heat of formation ofDicholoromethane CH H 416 kJmol CCl H 327 kJmol 2 x 416 2 x 327 Hforma on CH2C12 1308 kJmol Using AGO as a Predictive Tool AGO ZAGfO products AGfO reactants Of course AGO AHO 29815 A80 1 standard temperature T 25 0C or 29815 K The entropy change for a reaction is the difference between the absolute entropies of reactants and products A80 Z S0 products So reactants Q When is S O A At absolute zero for a perfectly crystalline solid Now what is the relationship between AG and the Equilibrium Constant K recall K AaBb aAbB CCdD
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