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Coordination Chemistry

Coordination Chemistry. Coordination Chemistry. Werner/Jorgensen Controversy. Alfred Werner. Sophus Jorgensen.

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Coordination Chemistry

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  1. Coordination Chemistry

  2. Coordination Chemistry

  3. Werner/Jorgensen Controversy Alfred Werner Sophus Jorgensen “Probably the greatest conceptual contribution to inorganic chemistry—comparable in both direct and indirect impact to the concept of the tetrahedral carbon atom in organic chemistry—is Alfred Werner’s concept of coordination compounds and his general theory of how they behave.” Albert Cotton

  4. Chelation • Metals are able to bind or chelate (greek to claw) to other molecules or ions in solution called ligands • Common Ligands are Lewis bases (electron pair donors) • Monodentate Bidentate • Common Metal ions are Lewis acids (electron pair acceptors) • Coordinate Covalent bonds are formed L → M • Complexes using polydentate ligands are called chelates

  5. Table 24.3 Some Common Polydentate Ligands (Chelating Agents)

  6. 24-1Werner’s Theory of Coordination Compounds: An Overview • Compounds that contain metal complexes are called coordination compounds. • CoCl3 and NH3. • [Co(NH3)6]Cl3 and [CoCl(NH3)5]Cl2 • Differing reactivity with AgNO3. Alfred Werner 1866-1919

  7. Werner’s Experiment • As a 26 year old lecturer Werner did the following experiment • Wener proposed that metals exhibit both primary and secondary valences

  8. Werner’s Theory • Two types of valence or bonding capacity. • Primary valence (oxidation number). • Based on the number of e- an atom loses in forming the ion. • Secondary valence (coordination number). • Responsible for the bonding of other groups, called ligands, to the central metal atom. [Co(NH3)6]Cl3 → [Co(NH3)6]3+ + 3 Cl- [CoCl(NH3)5]Cl2 → [CoCl(NH3)5]2+ + 2 Cl-

  9. Coordination Number

  10. Ethylene Diamine

  11. EXAMPLE 24-1 Relating the Formula of a Complex to the Coordination Number and Oxidation State of the Central Metal. What are the coordination number and oxidation state of Co in the complex ion [CoCl(NO2)(NH3)4]+? Solution: The complex has as ligands 1Cl, 1NO2, 4NH3 . The coordination number is 6.

  12. EXAMPLE 24-1 Charge on the metal ion:

  13. Isomerism Werner predicted there would be only two isomers of [CoCl2(NH3)4]+ and mailed them to Jorgensen. He received the Nobel prize in 1913.

  14. Isomerism

  15. Examples of Structural Isomerism Ionization Isomerism [CrSO4(NH3)5]Cl [CrCl(NH3)5]SO4 pentaaminsulfatochromium(III) chloride pentaaminchlorochromium(III) sulfate Coordination Isomerism [Co(NH3)6][CrCN6] [Cr(NH3)6][CoCN6] hexaaminecobalt(III) hexacyanochromate(III) hexaaminechromium(III) hexacyanocobaltate(III)

  16. Linkage Isomerism

  17. Stereoisomerism: Geometric Isomerism

  18. Geometric Isomerism How many isomers would [CoCl3(NH3)3] have?

  19. Geometric Isomerism

  20. Optical Isomerism Chiral shapes are not super imposable on their mirror image

  21. Chirality or Handedness Triethylenediamine cobalt(III) is a chiral molecule it differs only in how it interacts with another chiral object. “You can not put a right handed glove on a left hand”. Left and right circularly polarized light is an example of a chiral object.

  22. Optical Isomerism enantiomers

  23. Optical Activity dextrorotatory d- levorotatory l- We are made up of chiral molecules –l-amino acids, protein alpha helix, the DNA duplex, and sugars.

  24. 24-3 Nomenclature • In names and formulas of coordination compounds, cations come first, followed by anions. • Anions as ligands are named by using the ending –o. • Normally: • – ide endings change to –o. • – ite endings change to –ito. • – ate endings change to –ato. • Neutral molecules as ligands generally carried the unmodified name. • If the complex is an anion the ending –ate is attached to the name of the metal.

  25. Table 24.2 Some Common Monodentate Ligands. – ide endings change to –o – ate endings change to –ato

  26. 24-5 Bonding in Complex Ions: Crystal Field Theory • Consider bonding in a complex to be an electrostatic attraction between a positively charged nucleus and the electrons of the ligands. • Electrons on metal atom repel electrons on ligands. • Focus particularly on the d-electrons on the metal ion.

  27. Octahedral Complex and d-Orbital Energies

  28. Electron Configuration in d-Orbitals Δ P Pairing Energy Considerations Hund’s Rule

  29. Spectrochemical Series Large ΔStrong field ligands CN- > NO2- > en > py  NH3 > EDTA4- > SCN- > H2O > ONO- > ox2- > OH- > F-> SCN- > Cl- > Br- > I- Small ΔWeak field ligands

  30. Electron Configuration in d-Orbitals

  31. Effect of Ligands on the Colors of Coordination Compounds

  32. Absorption Spectrum max

  33. Light Absorption and Transmission [Ni(H2O)6}2+ Ni(NH3)6]2+ [Ni(en)3]2+ Transmitted GreenBluePurple Absorbed (red)(orange)(yellow) 700 nm600 nm570 nm Do hc/l small medium large

  34. Werner’s Theory of Coordination Compounds • CoCl3 and NH3. • [Co(NH3)6]Cl3 and [CoCl(NH3)5]Cl2 Alfred Werner 1866-1919

  35. Presented by: Sudhir Kumar Maingi PGT CHEMISTRY K.V. No. 1 PATHANKOT, JAMMU REGION

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