TRANSITION METALS CHEM 416
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This 13 page Class Notes was uploaded by Carmela Kilback on Wednesday September 9, 2015. The Class Notes belongs to CHEM 416 at University of Washington taught by James Mayer in Fall. Since its upload, it has received 19 views. For similar materials see /class/192538/chem-416-university-of-washington in Chemistry at University of Washington.
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Date Created: 09/09/15
Coordination Number Table Chem 416 Coordination Name Comments 18 e for 2 ML2 linear rare except for CuI Agl Aul these are d10 14 total electrons 3 ML3 tri gonal rare 4 ML4 tetrahedral common d10 especially With larger ligands d orbital splitting 3 above 2 with At a 49 A0 square planar very common for d8 complexes With strong field ligands d8 gt 16 total electrons d orbital splitting 1 above 4 5 ML5 trigonal bipyramid tbp common for d8 d8 square pyramid Spy common for d8 d8 tbp and spy structures are usually very close in energy both have roughly 1 above 4 d orbital splittings 6 ML6 octahedral most common structure d6 trigonal prism rare 7 ML7 capped octahedron rare most common for d4 d4 pentagonal bipyramid the three structures capped trigonal prism are 01056 111 energy 8 ML8 dOdecahedron rare most common for d2 d2 square antiprism 9 MLg tricapped tri gonal prism rare most common for d0 d0 1751 laxaaa Newquot a i new euguog39 we ultnw suit 5 3 Real vecoordinatc structures illustrating 01 Sign left to C4 right reaction pathway Note that the two Ni CNquot39 polyhedra are present in the unit cell for crys ne en a t triangu imam e Ideahzed Polytopal Forms Description of Real and ca Molecules Referenced to Idealized Polygons or Polyhedra in Geometric Reaction Path Form tirniti 39 t e u E L Muetterties39 and L J Guggenberger g 552 Contribution No 2071 from the Central Research Department two sc E I du Pont de N emows and Company Experimental Station square Wilmington Delaware 19898 Received August 18 1973 5 Such al molecu 39 or tran Abstract Molecules or ions in the cluster and coordina 7 me rationalized for all xatom families in terms of idealized g i d z with cubic symmetry explicit descriptions of polyhedra or It is sometimes difficult to distinguish between reference id quot 1750 39 edi cal states Most precise data are derived from Xray stu T 39 D uI varying degrees from idealized models A comprehensive d Jig be readily obtained from the dihedral angles formed by t39 T ms r I presented in terns of reaction paths that interrelate p 39 these dihedral angle data be reported in structure investig l lecular geometry but also for the generation of extensive l 1 F the molecules or ions in the liquid solution or gaseous st 04 s 3 al 39 ecu I e l n irksome phrase encumbered with imprecise Tl T5 L35 English and often2 encountered in structural esa papers is the molecule is a distorted trigonal bipyr l 2 Lite d amid or octahedron square plane etc Certain aquot 1 2 idle t atoms in a molecule may describe precisely the vertices T 3 1 of a regular tetrahedron or may nearly describe the 353 vertices of some idealized polygon or polyhedron I 6 a 1095 5n 1 63 6 s 0 mm Such descriptions properly phrased and soundly a d based are of great value to the follower of structural 55139 2quot 6 139682396 4396l639 039 quotI OWO chemistry A more objective and quantitative assess Figure 2 Foumtom family shape characteristics for Mmimg Ey forms The double lines denote the reference edges for the shape 0 1749 39 determining 5 angles Mechanistically the interrelationships of w the two forms may be more readily apparent if the set 2 angles are n describedas 180 ratherthan0 ation f 1 ple at l i i 39 39 non I z r L J ants l The I I l I I I i 39 v 15 It 39 e hquot quot ana39 V uetiert 16 i 3 17 E f109 guru l Digonal twm mechanism for correlating fourcoordinate rahedral and square planar polyhedral forms A strict digonal ist converts the regular tetrahedron to a D1 rectangle If all isles are a110wed to change from 1095 to 90 then the digonal Figure 3 Berry rearrangement mechanism for interconversion 0 dst and the tetrahedral compression mechanisms are equivalent Du and Clu geometries in ML complexes id indistinguishable 3 04 as pivot 2 Trigonal bipyrameid a Trigonal bipyramid b 39 Tetragonal pyramid Figure 1213 Interchange of axial and equatorial positions by Berry pseudorotation BP R m 55 I an W ag39 t Q a 89 mm re goon py u da MK rmer Ltsi om bieyeewi amp 4 Eva at mam Fig 1011 The structures of the red square pyramidal isomer 3 and the green trigonal bipyramidal isomer b of the chlorobis12bisdiphenylphosphinoethanecobaltII cation Phenyl groups and other substituents have been removed for clarity From J K Stalnick et al Inorg Che m 1973 12 1668 Reproduced with permission Chem416 Energies and Spectroscopies NMR EPR IR Vis UV Xray I I Hz 3x108 3x1010 3x1012 3x164 3x166 3x168 3x1020 cm 1 102 1 100 104 106 108 1010 100 cm 1 cm 01 mm 1 micron 100 nm 1 A 001 A 1 kcal 1 00 kcal 1eV 1 K 300 K quotIi T2 1 sec nsecpsec 024 kJ mol391 2 1 kcal mol391 2 350 cm391 2 1 x 1013 Hz 2 503 K 004 eV 1 eV 2 965 kJ mol391 2 23 kcalmol391 8066 cm391 24 x 1014 Hz 1 K 07 cm391 I 2 x 1010 Hz 2 8 x 10393 kJ mol391 2 2 x 10393 kcal mol391 A factor of 10 in Keq at ambient temperatures 2 in terms of free energy 0059 eV 2 57 kJ mol391 2 137 kcalmol391 480 cm391 2 14 gtlt1013 Hz NMR nuclear spin ips EPR electron spin ips IR molecular Vibrations UVVis electronic transitions Chemistry 416 Symmetry and the Interaction of Orbitals 0r States All orbitals and states must have the symmetry of one of the irreducible representations of the point group of the molecule This holds for all orbitals of the central atom if there is one and for any symmetry adapted linear combinations of orbitals SALCs For two orbitals or two states to interact they must have the same symmetry the same irreducible representation Any two orbitals or states that have the same symmetry will likely interact and miX The overlap of two orbitals is given by willpz E fffw1w2dXdde The respresentation for LPl x 1P2 is the representation of Ipl times the representation of 1P2 When we integrate over all space the integrand Ipl x 1P2 must have a1 symmetry or else the integral will be zero Here s why What if the integrand didn t have a1 symmetry and changed sign about some mirror plane Then when we integrate over all space the result from one side of the mirror will cancel the result on the other side For Ipl x 1P2 to be a1 Ipl must have the same representation as 1P2 Chem416 Energies and Spectroscopies NMR EPR IR Vis UV Xray I I Hz 3x108 3x1010 3x1012 3x164 3x166 3x168 3x1020 cm 1 102 1 100 104 106 108 1010 100 cm 1 cm 01 mm 1 micron 100 nm 1 A 001 A 1 kcal 1 00 kcal 1eV 1 K 300 K quotIi T2 1 sec nsecpsec 024 kJ mol391 2 1 kcal mol391 2 350 cm391 2 1 x 1013 Hz 2 503 K 004 eV 1 eV 2 965 kJ mol391 2 23 kcalmol391 8066 cm391 24 x 1014 Hz 1 K 07 cm391 I 2 x 1010 Hz 2 8 x 10393 kJ mol391 2 2 x 10393 kcal mol391 A factor of 10 in Keq at ambient temperatures 2 in terms of free energy 0059 eV 2 57 kJ mol391 2 137 kcalmol391 480 cm391 2 14 gtlt1013 Hz NMR nuclear spin ips EPR electron spin ips IR molecular Vibrations UVVis electronic transitions Chemistry 41 6 Electronic Spectroscopy UVvis Typically in the ultraviolet and visible regions of the spectrum Transitions between electronic states with characteristic symmetries and spin multiplicities Electronic states are typically interpreted in terms of orbital occupancies when all the orbitals of a particular set a filled the state has 1A1g symmetry 0 The intensity of an electronic transition if proportional to the square of the matrix element I 0C lt1P9 111igt2 where subscript f indicates the final state and i the initial state in 39matrix element39 notation lt1P9 1Pgt is the integral over all space ffflt1Pl J 1Pdxdydz The Hamiltonian Gf is the electric field of the light that is being absorbed or emitted This is the interaction that couples the initial and final states It has the symmetry of a vector xyz In the Character Table for the point group of the molecule Gf has the symmetry of x y and z The matrix element must have the symmetry of the most symmetrical irreducible representation of the point group of the molecule A or A1 or Alg or else it will be zero 0 We typically separate the electronic e and vibrational V parts of the wavefunction 1P wewv This is in essence the Born Oppenheimer approximation Then for most electronic spectroscopy I 0 lt1l efklMwejgt2ltwvfklwwigt2 which implies that there is an electronic transition the first term whose shape is modulated by the vibrational overlaps called Frank Condon factors Vibrational progressions are seen in spectra when there is a change in the potential surface for that vibration between the ground and excited state absorption spectra show excited state vibrations emission spectra show ground state vibrations Within this level of approximation transitions where electrons move between d orbitals the d d transitions described by Tanabe Sugano diagrams have zero intensity by symmetry in space groups that have an inversion center They are forbidden because the we wavefunctions are g in symmetry symmetrical with respect to i and Gf has u symmetry The function in the matrix element therefore has symmetry g X u X g u and will integrate to zero But d d transitions don t have zero intensity they are just are weaker than fully allowed transitions The most common way around this Laporte forbiddenness is that the excited state mixes in one vibration of u symmetry that the Born Oppenheimer separation of we and wv does not fully hold Then the electronic part of the matrix element is lt1pe1pvvf9 wgigt and it will have g symmetry if luv9 has u symmetry The one vibration that is mixed in is sometimes called the enabling vibration In groups without an inversion center transitions are not Laporte forbidden but they are still weak because the d orbitals are inherently g 0 As a rough guideline the intensities of transitions in transition metal complexes are spin forbidden eg 3A2g gt 1Tlg s lt 1 Laporte forbidden spin allowed eg 3A2g gt 3T152 8 5 100 Laporte allowed groups with no i eg 3A2 gt 3T1 8 ca 250 fully allowed eg charge transfer transitions 8 1000 50000 r A39s am 091 I TABLE 55 10Dq for bivalent rst row transition metal compounds estimated from lattice energies and heats of hydration Values are in cm TABLE 56 Con g d1 d2 d3 d4 d5 d6 d7 d3 d9 uration Ion Sc2 Ti2 V2 Cr2 Mn2 Fe C02 Ni2 Cu2 Ligand F 11000 4000 19000 22000 16000 11 17 Cl 19000 11000 17000 14000 15000 9 16 Br39 19000 12000 18000 13000 14000 10 19 f I 19000 11000 26000 15000 13000 5 1i39 0239 40000 16000 27000 15000 13000 10 121 82quot 20000 17000 15 11 2162 86 29000 20 12 31 Te 34000 22 13 H20 22000 11000 16000 15000 14000 15 c THERMODYNAMIC ASPECTS OF CRYSTAL FIELDS 87 IODq for trivalent rst row transition metal compounds estimated from lattice energies and heats of hydration d7 Ni3 d8 C113 do Zn3 Con g d d2 d3 d4 d5 d6 uration on Ti3 V Cr Mn3 Fe3 Co3 Ligand F 47000 33000 20000 26000 27000 C1 48000 32000 23000 32000 Br 49000 36000 20000 H20 48000 23000 25000 31000 39000 4 INTRODUCTION TO LlGAND n CHAR 20 Cr d3 j 000I45MerBF I5 I i e 8 I0 r 5 J Ol4lillllll4lllllllilillillll 20 7 J m e oozmcuamz Oh I I l 5 Cr239d j g c 010Min 075M H230 OlJlllLllilllll lllll 5000 I0000 l5000 20000 25000 30000 35000 cmquot 20 L Fe2 d h E quot Amonm FeC0z n I Mquotd 3 036M MntCIo 2 4 I c 005 C i 01 I iIlILIIILlIIIIiIIII 5000 0000 l5000 20000 25000 30000 35000 cmquot FIG 94 e f g h i The absorption spectra of aqueous solutions of rst transition series ions ELECTRONIC SPECTRA OF COMPLEX IONS b From the corresponding intercept on the vertical axis 3T1F 3Azg i 16 B 14500B 39 Hence for NiH20 B 905 cmquot lODq 8900 cmquot 5 Ti3dl o e oI43M1iCI O llll lllllillJllllllllllJiJJ IO Cu2 d9 00030 M CuClO2 b e 39 I 5 39 DIlllllllllll ililLl V3quotd2 j 39 00472M VCl043HCIO c e 5 j r oIIIIIIIIIIIIIIIIIIIIIIIIII Niz id d 5 5quot 00025MNiClO4z O I I I I 5000 l0000 cmquot IIiII IIIiIIIIIJI l5000 20000 25000 30000 35000 221 1 94 a b c d The absorption spectra of aqueous solutions of rst transition series ions The value of B for the free Ni2 ion is Table 33 1040 cm There is a reduction to about 90 of the freeion value for the interelectronic repul sion parameter upon incorporation of the ion into the complex
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