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Coordination Chemistry

Coordination Chemistry. L igands bonding to metals. Donor-Acceptor Complexes. Definitions. Lewis Acid = acceptor = usually a transition metal cation Lewis Base = donor = ligand = usually something with a lone electron pair

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Coordination Chemistry

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  1. Coordination Chemistry Ligands bonding to metals

  2. Donor-Acceptor Complexes

  3. Definitions Lewis Acid = acceptor = usually a transition metal cation Lewis Base = donor = ligand = usually something with a lone electron pair Coordination number = # of metal-ligand attachments (from the metal’s point of view) Denticity = # of attachments a ligand makes (from the ligand’s point of view)

  4. Common Ligands Monodentate Ligands: Halides: F-, Cl-, Br-, I- O2-, S2-, OH-, CN- NH3, H2O, CO Bidentate Ligands: Polydentate Ligands: heme, salen

  5. Monodentate complexes

  6. Monodentate complexes

  7. Bidentate ligand complexes Co(en)2Cl2 Ni(DMG)2

  8. Bidentate complexes Co(en)32+ Fe(phen)32+

  9. Polydentate complexes Co(salen)+ chlorophyll

  10. Fe-heme

  11. Polydentate complexes Fe-heme O2-Fe-heme

  12. Determining Metal Oxidation States [Ag(NH3)2]NO3 K2[NiCl4] [Co(en)2Cl2]Cl [Cr(H2O)4CO3]Br

  13. Chelate Effect Cd(CH3NH2)42+ vs. Cd(en)22+ Thermodynamics of Formation Ligands Ho (kJ/mol) So (J/K-mol) -TSo (J/mol) Go (kJ/mol) 4 CH3NH2 -57.3 -67.3 20.1 -37.2 2 en -56.5 +14.1 -4.2 -60.7 Another example: [Ni(NH3)6]2+ + 3 en  [Ni(en)3]2+ + 6 NH3 K = 109.67

  14. Isomerization in Coordination Compounds Do for octahedral Complexes

  15. Inner and Outer Spheres [Co(NH3)4Cl2]Cl H2O [Co(NH3)4(H2O)Cl]Cl2

  16. All compounds Structural (constitutional) Stereo linkage ionization hydration geometric optical [Co(NH3)5Cl]NO2 [Co(NH3)5NO2]Cl [Co(NH3)4Cl(H2O)]Cl2 [Co(NH3)4Cl2]ClH2O [Co(NH3)5SCN]2+ [Co(NH3)5NCS]2+

  17. Linkage Isomers

  18. Ionization Isomers

  19. Hydration Isomers

  20. Optical Isomers: enantiomers (mirror images) key to recognizing: no mirror planes of symmetry Type 1. arrangement of monodentate ligands Type 2. arrangement of bidentate ligands

  21. Geometric isomerism: like cis-trans

  22. Geometric isomerism Fac- isomer Mer- isomer

  23. Geometric Isomers: predicting numbers Use shorthand: M = metal a, b, c, etc. are different ligands Example 1: Co(NH3)4Cl2

  24. Example 2: Co(NH3)3BrCl2

  25. Example 3: Co(NH3)3enBr2+

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