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Types of Isomerism in Coordinate Compounds

Types of Isomerism in Coordinate Compounds. b. a. b. a. M M. a. b. a. b. Cis form Trans form. 1.GEOMETRIC ISOMERISM. More common in square planar complexes. b. a. b. a. b. b. a. M M. b. b. b. a. b. Cis form Trans form.

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Types of Isomerism in Coordinate Compounds

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  1. Types of Isomerism in Coordinate Compounds

  2. b a b a M M a b a b Cis form Trans form 1.GEOMETRIC ISOMERISM More common in square planar complexes.

  3. b a b a b b a M M b b b a b Cis form Trans form Octahedral Complexes

  4. b a a b M M b b a b Octahedral Complexes b a a a Meridional isomer Facial isomer

  5. 2.OPTICAL ISOMERS • Also called enantiomers. • They are non superimposible mirror images of each other. • Show chirality. • More common in octahedral complexes. • E.G. [Cr(C2O4)3]3- • [PtCl2(en)2] 2+ • [CrCl2(en)(NH3)2]+

  6. 3- 3- O O O O O O O O O O O OPTICAL ISOMERS Cr Cr O

  7. Recapitulation • Name the two types of stereo isomers? • What are the conditions necessary for geometric isomers? • Which property of optical isomers is different? • What are enantiomers?

  8. 3.IONISATION ISOMERS • It occurs when the counter ions in the coordination compound is itself a potential ligand. • They give different ions on ionization. • e,.g. [Co(NO3)(NH3)5]SO4 & [Co(SO4)(NH3)5] NO3 • [PtCl2 (NH3)4]Br2 & [PtBr2 (NH3)4] Cl2

  9. 3.HYDRATE ISOMERS • It is observed when water forms a part of coordination entity. • [Cr (H2O)6] Cl3 - Violet • [Cr Cl (H2O)5] Cl2.H2O- Pale Green • [Cr Cl2 (H2O)4] Cl.2H2O- Green

  10. 4.Linkage Isomers • These are possible in complexes containing ambidentate ligands. • E.g. [Co(NO2)(NH3)5]2+& • [Co(ONO)(NH3)5]2+

  11. 5.COORDINATION ISOMERISM • The cation & anion both are complex in such types of isomers. • They arise due to interchange of ligands between cation & anion entities. • [Co(NH3)6] [Co(CN)6]& [Cr(NH3)6] • [Co(CN)6] • [Cu(NH3)4] [PtCl4]& [Pt (NH3)4] [CuCl4]

  12. Recapitulation • Geomtetric isomer is common in ____________ & ______________complexes. • Compounds having water as a ligand show _________isomerism. • ____________ is a didentate ligand. • Linkage isomerism arises due to _________. • Optical isomers have same _____ properties but different __________ properties.

  13. Home Assignment • 1.What type of isomerism is exhibited by [PtCl2 (NH3)4]Br2 & [PtBr2 (NH3)4] Cl2?How will you differentiate between the two? • 2.Draw the optical isomer of [CrCl2(en)(NH3)2]+ • 3.Illustrate the following with an example. • Linkage isomer • Coordination isomer.

  14. VALENCE BOND THEORY • Given by Pauling in 1931. • Metal ligand bond arises by donation of pairs of electrons by ligands to metal ion. • Metal ions must have requisite no. of vacant d- orbitals of equal energy. • These orbitals of the metal atom hybridize to give a set of hybrid orbitals. • Some times the unpaired electrons pair up to make available a number of empty orbitals equal to its coordinatin no. • With the approach of ligands , metal ligand bonds are formed. • .

  15. COMPLEXES HAVING C.N.-6 • [Cr(NH3)6] 3+, [Fe(CN)6]3-, (Inner orbital)-low spin • [Co(F)6]3-(Outer orbital) -High spin • d2sp3 or sp3 d2 hybridization

  16. Square Planar [Ni(CN)4] 2- [Cu(NH3)4] 2+ dsp2 hybridization. Tetrahedral [Ni(CO)4] [Zn(NH3)4] 2+ sp3 hybridization COMPLEXES HAVING C.N.-4

  17. DRAWBACKS OF VALENCE BOND THEORY • Why some metal ion in a particular oxidation state are low spin while others are high spin. • The magnetic behaviour predicted by VBT is misleading. • It does not explain the colour of complexes.

  18. CRYSTAL FIELD THEORY • Given by Hans Bethe(1929) and John Vleck (1932). • They assumed that the metal ligand bond is ionic arising purely from electrostatic interactions between metal ion & ligand. • It treats each ligand as a point of negative charge. • It considers the effect of ligands on the relative energies of the d- orbitals of the central atoms.

  19. ∆0 CRYSTAL FIELD THEORYIN OCTAHEDRAL COMPLEXES dx2-y2,dz2 (eg) dxy, dyz ,dxz( t2g )

  20. The difference in the energy between two sets of d-orbitals is called crystal field splitting energy. • For any given metal ion , the magnitude of ∆0 depends on the nature of the ligands. • I- <Br-< S2-<SCN->Cl-<F-< OH-< C2O42-<O2-<H2O<NCS-<NH3<en<NO2-< CN-<CO • It is known as spectrochemical series .The ligands with small value of ∆0 are called weak field ligands while those with with larger value are called strong field ligands.

  21. CRYSTAL FIELD THEORYIN TETRAHEDRAL COMPLEXES dxy, dyz ,dxz( t2g ) ∆t dx2-y2,dz2 (eg)

  22. CRYSTAL FIELD THEORYIN SQUARE PLANAR COMPLEXES dx2-y2 dxy dz2 dxz, dyz

  23. Prepared By KIRAN DWIVEDI PGT CHEM KVISP, NASIK ROAD

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