General Chemistry (Continued)
General Chemistry (Continued) CHEM 1415
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Chemistry of Coordination Compounds Chapters 6 22 Chemistry 1st edition Julia Burdge 8122010 Outline Coordination compounds gt Electronic configurations or transition metals and metal ions possible hybridization scnemes gt Coordination compounds as a special cnemicai entity gt Anatomy or coordination compounds Odeathl i number coordination number orbitals geometry etc Complex coordination compounds Spin state and color properties of coordination com ou s Spin state and magnetic properties of coordination compounds Periodic Table 81 Determinethe electronic nfiarin f rniin mml n metal ions Readings 6869 Electron Configurations and Transition Elements Multiple Electron Atom 5 4 One Electron Atom 4 3 4 5 4 3 3 3 2 2 2 1 1 s p cl p ElCunr 1st Transition Series Note all have Ar core electronic configuration Ar 1s2 2s2 2p6 3s2 3p6 21 22 23 24 25 Sc T1 V Cr Mn 4sz3d1 452m2 4sz3d3 4sl3d5 4sz3d5 26 28 29 30 C Fe 27Co Ni 11 H 452m6 4sz3d7 452mS 4513d10 4523le Transition Elements and d Electrons Properties of transition metals gt more than one oxidation state except for So and Zn gt cations are usually found in complex ions gt colored cations gt magnetic properties d Electrons gt large number of bonding sites gt octet rule violated 8122010 Oxidation states of transition metals Transition metals are readily oxidized to form Ions During ionization n1s electrons are lost before nd electrons Filled and halffilled d shell is more stable 3B 43 SB 68 7B BB 15 23 8 0 6 n I O o u 4 O O I o o O a o O I I O c u 2 0 o o I O O O O O C SC Ti V Cr Mn IFe Co Ni Cu Zn Transition metals can accommodate up to six electron domains TABLE 91 ElectronrDomain Geometries a39 n Funulun or the Number ol Electron Domains Numbmof Arrangemcnl of Elecli39onDumain Predicted Electton Domains Elcch nn Domains Ccnmelry Bond Angles z i annr iso v39 Irigmml 120 planar TABLE a l Hmmwounnnn Geomeniea a n Fululinn m the Nmnlm or Elm mm Dmnaim Number of Arrangcnlml of Electronrlhmnin I mdicled Electron Domains Electraquot Damains Cnomvlry 30nd Angles 4 I39clrahmtrdl lll9fw r mq v l 20 70 igun lxlpymmidnl ml edrul v Copyright c 2006 Pearson Prenllce Hall lnc Complexes Transition metals often form metal complexes i a If the complex bears a charge It Is a complex Ion Compounds containing 0 complexes are called coordination compounds The molecules or ions coordinating to the metal are called the ligands They are usually anions or polar molecules 0 9 8122010 Coordination Compounds TABLE 241 Properties of Some Ammonia Complexes of CobalttIIIl Original Ions per quotFreequot Cl Ions Modem Formulation Color Formula Unit per Formula Unit Formulation C0C13396 NH3 Orange 4 3 CoNHQhJClg CoCl35 NH Purple 3 2 CoNll35ClClz C0C134 NH Green 2 l il nllsClNH3C12Cl C0C13 4 NH Violet 2 l cisC0NH3CJZCI Many coordination compounds are brightly colored Coordination compounds with the same metal and ligands can release different numbers of ions when they dissolve or have different colors Werner s Theory 0 Alfred Werner suggested in 1893 that metal ions exhibit primary and secondary valences gt Primary valences are the oxidation numberforthe metal 3 on the cobalt at e the right gt Secondary valences are the coordination number the number of atoms directly bonded to the metal 6 in the complex at the right The central metal and the ligands directly bonded to it make up the coordination sphere of the complex Ilc go 0 Werner s Theory Werner proposed putting all molecules and ions within the sphere in brackets and those free anions that dissociate from the complex ion when dissolved in water outside the brackets TABLE 241 Properties of Some Ammonia Complexes of Cobaltlllli Original lons per quotFreequot or loos Modern Formulation Color Formula Unil per Formula Unit r CoC11396 NHt Orange 4 3 CoNHMCl3 CnCllS NHI Purple 3 2 lCoNHCIICl2 CuClgAN 2 n 2 1 C CoClx39i NHl Violet 2 l Werner s Theory This approach correctly predicts there would be two forms of CoCl3 4 NH3 gt The formula would be written CoN H34Cl2Cl gt One of the two forms has the two chlorines next to each other gt The other has the chlorines opposite each other MetalLigand Bond The bond between the metal and the ligand is a bond between a Lewis acid and a Lewis base gt The ligands Lewis bases have nonbonding electrons gt The metal Lewis acid has empty orbitals If the coordinated compound is charged it w fo ionic bond with counterions If i1 H Aguq Zlel qu H lTlIAgZN H aq H H H 82 Recognize and identify coordination compounds and their components Readings 221 8122010 Coordination Compounds Complexes ML l Transition Metal Ion Ligand Lewis Acid Lewis Base Common ligands increasing strength Cl39 lt P lt H20 lt NH3 lt en lt N0239 lt CN en ethylenediamine 83 Determine oxidation number coordination number orbitals used in bonding and geometry of the central metal atom in coordination compounds and complexes Readings 221 222 Example CoNH3ClCl2 Total charge of the complex charge on the central ion sum of charges of the ligands CoNH3Cl2 i i T i x 0 1 2 Answer oxidation state on Co is 3 Coordination Number The atom of the ligand that supplies electrons for the 7 metal is the donor atom O NHquot imn g The number of these atoms a 7 a O J x39ZF L39JMC is the coordination number 0 Some metals have the same 39 coordination number eg 6 N H gt W for Cr3 and Co 4 for Pttz M m 0 Possible coordination m quothim kquotw numbers are 2 4 and 6 va W 0 Larger ligands and ligands w m that transfer greater charge to the metal have smaller coordination numbers Geometries and hybridization Two common O NHquot 2 NH geometries for metals with a coordination An 0 395 number of four Q gt Tetrahedral 7 gt Square planar SP3 dsp2 When the m 7 NH coordination number N 39 m i is six the geometry is M W Cu octahedral X M Forlinear geometry V 7 w hybridization is sp d23p3 Coord Examples Ox Crd Geo Orb CuNH3Cl 1 2 linear sp Amminechlorocopperl CrNH36 N033 3 6 octa dzsp3 Hexaamminechromiumlll Nitrate K3 FeCN5CO 2 6 octa dzsp3 Potassium Carbonylpentacyanoferratell ZnNH32CI2 2 4 tetra sp3 Diamminedichlorozincll Pten2 Cl2 2 4 sq plnr dsp2 Bisethylenediamineplatinumll Chloride 84 Describe the bonding effects of polydentate ligands Readings 221 225 Polydentate Ligands Some ligands have two or 3 more donor atoms These are called polydentate ligands In hinl ethylenediamine en a donor atom In general polydental ligands form a more stable Coengt3J3 complex with metal than monodental ones NHZCHZCHZNHZ each N is amp Coen3 Polydentate Ligands Polydental componds act as Chelating agents gt EDTA has six donor atoms gt Polyphosphates chelate Mg2 H H H and Ca2 eg from hard water NaR VO P O lr OIO Chelators inactivate metals 0 0 0 without removing them from solution 1 I iCCHK CH3C N H xCHZCHZN W Q CHZ CHZ LTQV 1 u 0 EDTA L DTAF39 Chelating Agents The tetradental porphine is the business end of porphyrins which encase metals for various fundamental biological functions Important biomolecules like heme and chlorophyll are porphyrins chlorophyll heme 8122010 85 Given their formulas name coordination compounds and complexes and vv Readings 221 Nomenclature for Coordination Compounds Compounds are named as salts cation before anion Ligands are named before metal ions in alphabetical order regardless of charge gt Prefixes are not part of the name gt In Writing metal listed tll St Name anion ligands with an quotoquot suffix eg fluoro chloro cyano hydroxo neutral ligands with molecular name gt Exceptions H20 aqua NH3 ammine CO carbonyl NO nitrosyl Nomenclature for Coordination Compounds Number of ligands is indicated by Greek prefix mono di tri tetra penta amp hexa gt If the name of the ligand contains di tri etc put parenthesis around the ligand and use alternate prefixes bis tris tetrakis pentakis amp hexakis Oxidation state of metal ion is shown in parentheses in Roman numeral If complex ion is anion add ate to name of metal gtsometimes Latin names are used Fe ferrate Ag argenate Cu cuprate Au aurate Pb plumbate Sn stannate Some common ligands Name in Name in Ligand Complexes Ligand Complexes Azidc N Alida Oxalate C2042 Oxalnto Bromide Br Bromo Oxide Ozquot Oxo Chloride C17 Chloro Ammonia NH Amminc Cyanide CN 39 Cyano Carbon monoxide CO Carbon Fluoride F 7 Fluoro Ethylenediamine en Elhylenediamine Hydroxide OH Hydroxo Pyridine CquN Pyridine Carbonate C0327 Carbonate Water HZO Aqua Practice Give the correct name for each of the following coordination compounds or complex ions a CoNH35C1C12 b Feen1N0222804 c CoCNFSCN2239 d K2C0CNFSCN2 e K3FeCN6 Examples Give the correct chemical formula for each of the following coordination compounds or complex Ions a triamminebromoplatinumll chloride b potassium hexafluorocobaltatelll c trisethylenediaminenickelll d diaquadicarbonylnitritonitrosylvanadiuml e tetraamminebromohydroxomanganeseVll sulfate 8122010 lsomers 86 Recognize describe and identify structural isomers coordination amp linkage and stereoisomers geometrical and optical of coordination complexes Readings 222 lsomers lsomers have the same molecular formula but their atoms are arranged either in a different order structural isomers or spatial arrangement stereoisomers lsomers Coordination lsomers Coordinationsphere isomers differ in what ligands are bonded to the metal and what is outside the coordination sphere Examples gt The violet CrH206Cl3 gt The green CrH205CIC2 H20 and gt The also green CrH204CI2C 2 H20 Coen3Crox3 and Cren3Coox3 8122010 Linkage Isomers If a ligand can bind to the metal with one or 39 another atom as the 7 donor atom linkage isomers are formed V V o 39 a Iquot a a l v O 39 can on Vla Or 039 390 N02 can bond via N or O itm isomer Nimm mms39r A Geometrical Isomers With these geometric isomers two chlorines and two NH3 groups are bonded to the platinum metal but are clearly different ham gtcislsomers have like groups on the same side gttrans lsomers have like groups on opposite sides Optical Isomers l 1 l 0453quot silk1 g or I I E l 3 o l f Coen3 Optical isomers or enantiomers are mirror images of each other Just as a right hand will not fit into a left glove two enantiomers cannot be superimposed on each other A molecule that exists one of possible enantiomers is called chiral Optical Isomers Nonsuperimposable mirror images left hand right hand Chiral species gtNot ever geometrical isomer is chiral Enantiomers gtdextrorotatory d rotates to right gtlevorotatory I rotates to left Many biological molecules are chiral Detect by rotation of plane polarized light Optical actIVIty The physical properties of chiral molecules are the same exceptin instances where the spatial placement of atoms matters Chiral molecules are optically active ie can rotate light 0 Two enantiomers rotate planepolarized light to the same extent in opposite directions Polarizing Unpolarizcd filler lighl mla un of v p Ana 039 lz V polarization RUM L d polarized light l m V 4 ll I Optically aclivc PolarIZCI Pula 78d 0 ll rion OptActivity Xquot 8 Analyzel Polarize Example Quiz Does CoNH3Bren22 exhibit geometrical isomerism optical isomerism 8122010 Trans Isomers Cis Isomers 87 Explain spin state and the magnetic and color properties of transition elements Readings 223 88 Relate and predict electronic structure field strength A spin state and magnetic and color ro erties of coordination com lexes in octahedral tetrahedral and square planar environments Readings 223 89 Relate and predict electronic structure field strength A spin state and magnetic and color properties of coordination complexes based on ligand strength Readings 223 39 Co quot C l1H3 H3N Br Br 0 Color Visible spectrum is 400 nm to 800 nm If a color is missing from the spectrum the light will have a complementary color 0 580m For liht Color Com lement White y Dyes absorb a specific color and mm 560nm transmit the rest 650 nm V 0 For dyes Color Complement Black 430quot 5 quot7490 R O Y C B I V 1R UV I 600 nm 00 nm 400nm 5 Wavelength 8122010 Complexes and Color Absorption of light 1 Energy of light The complex ion E 71 hC1 Squot T39H29e3 absorbs Light can be absorbed if for any green 91m and electron in the molecule the 3 hva energy difference between E therefore appears U Purple red P39US excited state and ground state Violet ends of the A hV So spectrum U For most electrons the energy gap is too large to absorb visible light Jill Sill llll 700 Navelength lnmi Magnetism Crystal field theory 0 The electron pairfromthe ligand m destabilizes delectrons on the 1 MAM Molecules with unpaired electrons are metal 7 f paramagnetic and are pulled into magnetic As a reSUIt39 the energy levels f r g i quot7 N f Id delectrons Increases will Li le 0 Some dorbitals are affected il l ln ferromagnetic materials paramagnetic strongerthan others The energy levels for dorbitals molecules are cooperating with each other lit39 th I39 d f39 Id Molecules Without unpaired electrons are Sp m 9 mm s 399 diamagnetic and are repelled weakly from r DML 7 Dd Cami 39 magnetic field Bond dipole Empty hybrid Filled 5 73 Resulting molecular orbital Orbital on metal hybrid orbital of 1 bond between metal on ammonia and ammonia Copynghl m 2006 Pearson Prisr ice Haii Inc d orbitals in octahedral field CompIexes and coor dzz and dX2y2 Common ligands increasing strength Olrbitali Tsetdare 3 l39 lt Br lt Cl39 lt P lt H20 lt NH3 lt en lt N0239 lt CN39 coser O igan S quot r in quot 3 1r and are affected 39 9 T strongerthan the i d d Stronger ligands induce larger Va A Zetjbga39s dxr 22 Xz39yz Greater charge on metal induces larger 0 Th stronger the x LNX kg gap ligand the greater The larger the gap A the shorter the the split I a Ivy absorbed light dxy dyz dxz Energy Complexes and Color The larger the gap the shorter the wavelength of absorbed light Therefore the wavelength of observed light in the complex is longer closer to the red end of the spectrum m m mm m I Vanadate lCerlj39 ll39ll39ll h OM1 ClNHJRJL CrlCNlnl1 39 Green Vinlel Yellow Yellow Strong and weak field 0 Split between dorbitals can be greater than the spinpairing energy When split between dorbitals is large the Hund rule appears violated Field strength Splitting A Spin strong large low weak small high Co3 in Strong vs Weak Field Co3 is a 3d6 ion 9 largeA 99 l39 l I smaHA tzg 4e 4 4i tzg 4 t 4 Strong Field Weak Field Large A Small A Low Spin High Spin 69 COCNe339 69 COCe339 Co3 in Strong vs Weak Field 9 largeA eg 1 l I smaHA tzg 49 4 4b t2g ll l 4 69 C0C6l339 paramagnetic Induced magnetic properties determined by the number of unpaired electrons 69 C0CN6l339 diamagnetic Magnetic Properties Setup NaCl H20 d5 Mn2 d6 Fe2 d7 Co2 d8 Ni2 dw Zn2 FeCN6 CoNH36 NiNH36 MnVll Mnlll MnlV Octahedral and Tetrahedral Splitting Octahedral Tetrahedral dz2 dx2y2 dxy dxz dyz dzz dX2y2 dxy dXZ dyz Fortetrahedral complexes splitting is always small spin is always high 8122010 11 Other Splitting Patterns d it1 Linear E5 L1H leZ amp dyZ 5 dz dXy amp dX2y2 dxzr 1 Octahed ral Square planar Cumugmems Pearson Frantic Hall lm 8122010 1 Isomers Even Possible For which basic geometries are isomers even possible Structural Stereo BasicGeom Coord Linkage Geom Optical Linear Y Y Tetrahedral Y Y Y Sq Planar Y Y Y 9 Octahedral Y Y Y Y 12