Variety in Coordination Modes of Ligands in Metal Complexes

1 Introduction.- 1.1 Classification of Ligands.- 1.2 Linkage Isomerism.- 2 Monoatomic Ligands.- 2.1 Coordination Modes for the Hydride Ligand.- 2.1.1 Terminal Hydride Ligands.- 2.1.1.1 Preparative Methods.- 2.1.1.2 Characterization.- 2.1.1.3 Tricapped Trigonal Prism Structure.- 2.1.1.4 Octahedral Structure.- 2.1.1.5 Pentagonal-Bipyramid Structure.- 2.1.1.6 Trans Influence of the Hydride Ligand.- 2.1.2 Unsupported M-H-M Linkage.- 2.1.3 Dinuclear M(µ-H)nM and Mixed-bridged Systems.- 2.1.3.1 Preparative Methods.- 2.1.3.2 Characterization.- 2.1.3.3 M(µ -H)2M Systems.- 2.1.3.4 M(µ-H)3M Systems.- 2.1.3.5 M(µ-H)4M Systems.- 2.1.3.6 M(µ-H)(µ-X)n Systems.- 2.1.4 Edge-bridging (µ2) and Face-bridging (µ3) Hydride Ligands in Metal Clusters.- 2.1.5 Systems with an Interstitial Hydrogen Atom.- 2.1.6 Metal Clusters Including an Interstitial Light Atom other than Hydrogen.- 2.2 Chemical Reactions of Hydride Ligands.- 2.2.1 Reactions with Acids.- 2.2.2 Reactions with Bases.- 2.2.3 Reactions with Halogens and Organic Halides.- 2.2.4 Intramolecular Migratory Insertion.- 2.2.5 Reductive Elimination Reactions.- 2.3 Role of Rhodium Hydride Complexes in the Catalytic Hydrogenation of Olefins.- 2.3.1 Homogeneous Activation of Dihydrogen by Metal Complexes in Solution.- 2.3.1.1 Three Modes of H2 Activation.- 2.3.1.2 Dihydride Formation by Oxidative Addition of H2.- 2.3.1.3 Dihydrogen Complex.- 2.3.2 Reaction Pathway for the Hydrogenation of Olefins Catalyzed by RhCl(PPh3)3.- 2.3.3 Hydrogenation of Olefins Catalyzed by Cationic Rh(I) Complexes, [Rh(PP)(S)2]+.- 2.3.3.1 Formation of Cationic Rh (I) Complexes.- 2.3.3.2 Mechanism of Olefin Hydrogenation.- 2.3.3.3 Asymmetric Hydrogenation.- 3 Diatomic Ligands.- 3.1 Coordination Modes for Carbon Monoxide.- 3.1.1 Terminal Bonding and µ(C) Bridging.- 3.1.2 Mx-CO-M? Bridging.- 3.1.2.1 M-CO-M? Systems.- 3.1.2.2 M2-CO-M? Systems.- 3.1.2.3 M3-CO-M? Systems.- 3.1.3 CO Bridge Involving the ?2 (side-on) Linkage.- 3.1.3.1 µ(?1,?2) Mode.- 3.1.3.2 µ3(?1,2?2) Mode.- 3.1.3.3 µ4(3?1,?2) Mode.- 3.2 CO Cleavage and Reduction.- 3.3 Coordination Modes for Dinitrogen.- 3.3.1 End-on Unidentate Coordination.- 3.3.2 End-on Bridging.- 3.3.3 End-on µ3-Bridging.- 3.3.4 Side-on Coordination.- 3.3.5 Side-on Bridging.- 3.3.6 End-on: side-on µ3-Bridging.- 3.4 Protonation of the Coordinated Dinitrogen.- 4 Triatomic Ligands.- 4.1 Coordination Modes for the Thiocyanate Ion.- 4.1.1 One-end Bridging.- 4.1.1.1 µ(N) Bridging.- 4.1.1.2 µ(S) Bridging.- 4.1.1.3 µ3 (S) Bridging.- 4.1.2 End-to-end Bridging.- 4.1.2.1 Single µ(S,N) Bridging.- 4.1.2.2 Double µ(S,N) Bridging.- 4.1.2.3 µ3(2S,N) Bridging.- 4.1.2.4 µ4(3S,N) Bridging.- 4.2 Infrared Spectroscopy for Determining the Coordination Modes of the Thiocyanate Ligand.- 4.3 Factors Influencing the Relative Stabilities of the N-bonded and S-bonded Thiocyanate Complexes.- 4.3.1 Principle of Hard and Soft Acids and Bases (HSAB).- 4.3.2 Electronic Effects of Ancillary Ligands.- 4.3.3 Steric Effects of Ancillary Ligands.- 4.3.4 Solvent and Counterion Effects.- 5 Polyatomic Ligands: ?-Dicarbonyl Compounds.- 5.1 Three Coordination Modes for Neutral Molecules.- 5.1.1 Keto-enol Tautomerism and Structures of Enol Molecules.- 5.1.2 Metal Complexes of Neutral Molecules.- 5.1.3 O,O?-Chelation of the Keto Molecules.- 5.1.4 O-Unidentate Coordination of Enol.- 5.1.5 ?2(C,C?) Coordination of Enol.- 5.2 Coordination Modes for Monoanions.- 5.2.1 O,O?-Chelation and Bridging.- 5.2.2 Central Carbon Bonding and C,O,O?-Bridging.- 5.2.3 Outer-Sphere Coordination.- 5.2.4 O-Unidentate Linkage.- 5.2.5 ?Allylic Coordination.- 5.2.6 Terminal Carbon Bonding.- 5.3 Coordination Modes for Dianions.- 5.3.1 Central Carbon Bonding.- 5.3.2 Chelation through Terminal Carbons.- 5.3.3 Dienediolate Chelation.- 5.3.4 C,O,O?-Bridging.- 5.3.5 ?-Allylic Coordination.- 5.3.6 C,O-Chelation.- 5.3.7 ?3,O,O?-Bridging.- 5.4 ?3,C,O-Bridging of the Acetylacetonate Trianion.- 5.5 Concluding Remarks.- 6 Abbreviations.- 7 References.