1. 1 Transition Metal Chemistry and Coordination Compounds Chapter 22 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. 2 The Transition Metals

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5. 5 Oxidation States of the 1 st Row Transition Metals (most stable oxidation numbers are shown in red)

6. 6 Ionization Energies for the 1 st Row Transition Metals

7. 7 ScandiumTitaniumVanadium ChromiumManganeseIron CobaltNickelCopper

8. 8 Coordination Compounds A coordination compound typically consists of a complex ion and a counter ion. A complex ion contains a central metal cation bonded to one or more molecules or ions. The molecules or ions that surround the metal in a complex ion are called ligands. A ligand has at least one unshared pair of valence electrons H O H H N H H Cl - C O

9. 9 Coordination Compounds The atom in a ligand that is bound directly to the metal atom is the donor atom. H O H H N H H The number of donor atoms surrounding the central metal atom in a complex ion is the coordination number. Ligands with: one donor atom monodentate two donor atoms bidentate three or more donor atoms polydentate H 2 O, NH 3, Cl - ethylenediamine EDTA

10. 10 Coordination Compounds H 2 N CH 2 CH 2 NH 2 bidentate ligand or [Co(en) 3 ] 2+

11. 11 polydentate ligand (EDTA) [PbEDTA] 2- Bidentate and polydentate ligands are called chelating agents

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13. 13 What are the oxidation numbers of the metals in K[Au(OH) 4 ] and [Cr(NH 3 ) 6 ](NO 3 ) 3 ? OH - has charge of -1 K + has charge of +1 ? Au + 1 + 4x(-1) = 0 Au = +3 NO 3 - has charge of -1 NH 3 has no charge ? Cr + 6x(0) + 3x(-1) = 0 Cr = +3

14. 14 Naming Coordination Compounds The cation is named before the anion. Within a complex ion, the ligands are named first in alphabetical order and the metal atom is named last. The names of anionic ligands end with the letter o. Neutral ligands are usually called by the name of the molecule. The exceptions are H 2 O (aqua), CO (carbonyl), and NH 3 (ammine). When several ligands of a particular kind are present, the Greek prefixes di-, tri-, tetra-, penta-, and hexa- are used to indicate the number. If the ligand contains a Greek prefix, use the prefixes bis, tris, and tetrakis to indicate the number. The oxidation number of the metal is written in Roman numerals following the name of the metal. If the complex is an anion, its name ends in –ate.

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16. 16 What is the systematic name of [Cr(H 2 O) 4 Cl 2 ]Cl ? tetraaquadichlorochromium(III) chloride Write the formula of tris(ethylenediamine)cobalt(II) sulfate [Co(en) 3 ]SO 4

17. 17 Structure of Coordination Compounds 2 4 6 Linear Tetrahedral or Square planar Octahedral Coordination numberStructure

18. 18 Structure of Coordination Compounds Stereoisomers are compounds that are made up of the same types and numbers of atoms bonded together in the same sequence but with different spatial arrangements. Geometric isomers are stereoisomers that cannot be interconverted without breaking a chemical bond. cis-[Pt(NH 3 ) 2 Cl 2 ] trans-[Pt(NH 3 ) 2 Cl 2 ]

19. 19 Structure of Coordination Compounds cis-[Co(NH 3 ) 4 Cl 2 ]trans-[Co(NH 3 ) 4 Cl 2 ] Are these additional geometric isomers of [Co(NH 3 ) 4 Cl 2 ]? cis trans

20. 20 Structure of Coordination Compounds Optical isomers are nonsuperimposable mirror images. cis-[Co(en) 2 Cl 2 ]trans-[Co(en) 2 Cl 2 ] optical isomers chiral not optical isomers achiral

21. 21 Structure of Coordination Compounds Chiral molecules are optically active. Rotate the plane of polarized light. Polarimeter

22. 22 Bonding in Coordination Compounds All equal in energy in the absence of ligands! d-orbital orientation relative to x, y, and z axes

23. 23 Bonding in Coordination Compounds Isolated transition metal atom Bonded transition metal atom Crystal field splitting (  ) is the energy difference between two sets of d orbitals in a metal atom when ligands are present

24. 24 Bonding in Coordination Compounds  E = h

25. 25 The absorption maximum for the complex ion [Co(NH 3 ) 6 ] 3+ occurs at 470 nm. What is the color of the complex and what is the crystal field splitting in kJ/mol? Absorbs blue, will appear orange.  = h hc = (6.63 x 10 -34 J s) x (3.00 x 10 8 m s -1 ) 470 x 10 -9 m = = 4.23 x 10 -19 J  (kJ/mol) = 4.23 x 10 -19 J/atom x 6.022 x 10 23 atoms/mol = 255 kJ/mol

26. 26 Bonding in Coordination Compounds I - < Br - < Cl - < OH - < F - < H 2 O < NH 3 < en < CN - < CO Spectrochemical Series Strong field ligands Large  Weak field ligands Small 

27. 27 Colors of Some Transition Metal Ions Ni 2+ Cu 2+ Fe 3+ Cr 3+ Ti 3+ Mn 2+ Co 2+

28. 28 Bonding in Coordination Compounds weak ligand field strong ligand field

29. 29 Orbital Diagrams for High Spin and Low Spin Octahedral Complexes

30. 30 Crystal Field splitting in a Tetrahedral Complex

31. 31 Crystal Field splitting in a Square Planar Complex

32. 32 Reactions of Coordination Compounds Exchange or substitution reactions Stability Kinetic lability: tendency to react Unstable in acid solution Reaction takes several days to complete Complex is inert. Labile complexes react rapidly.

33. 33 Chemistry In Action: Coordination Compounds in Living Systems

34. 34 Chemistry In Action: Cisplatin – The Anticancer Drug