Coordination Chemistry ligands 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 Coordination number = # of metal-ligand attachments Denticity = # of attachments a ligand makes
Common Ligands Monodentate Ligands: Halides: F-, Cl-, Br-, I- O2-, S2-, OH-, CN- NH3, H2O, CO Bidentate Ligands: Polydentate Ligands: heme, salen
Monodentate complexes
Monodentate complexes
Bidentate ligand complexes Co(en)2Cl2 Ni(DMG)2
Bidentate complexes Co(en)32+ Fe(phen)32+
Polydentate complexes Co(salen)+ chlorophyll
Fe-heme
Polydentate complexes Fe-heme O2-Fe-heme
Determining Metal Oxidation States [Ag(NH3)2]NO3 K2[NiCl4] [Co(en)2Cl2]Cl [Cr(H2O)4CO3]Br
Isomerization in Coordination Compounds Do for octahedral Complexes
Inner and Outer Spheres [Co(NH3)4Cl2]Cl H2O [Co(NH3)4(H2O)Cl]Cl2
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]ClH2O [Co(NH3)5SCN]2+ [Co(NH3)5NCS]2+
Linkage Isomers
Ionization Isomers
Hydration Isomers
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
Geometric isomerism: like cis-trans
Geometric isomerism Fac- isomer Mer- isomer
Example 1: Co(NH3)4Cl2 Geometric Isomers: predicting numbers Use shorthand: M = metal a, b, c, etc. are different ligands Example 1: Co(NH3)4Cl2
Example 2: Co(NH3)3BrCl2
Example 3: Co(NH3)3enBr2+