Transition-metal-coordinated carbonyls

Carbonyl Complexes of the Transition Metals Coordination Numbers Geometries Coordination Organometalhc Chemistry Principles Diffraction Methods in Inorganic Chemistry Molecular Orbital Theory. 

There are a number of different types of polymers that contain metal carbonyl complexes attached to polymer backbones and side chains. In the 1970s, Pittman and coworkers reported the synthesis and polymerization of a wide range of vinyl monomers containing transition-metal-coordinated cyclopentadienyl rings. Polymer 21 is an example of a copolymer containing chromium and manganese complexes in the side chain. Another class... 

This is a special volume of Inorganic Syntheses that focuses on complexes that are likely to be useful as starting materials for the preparations of new transition metal coordination and organometallic compounds. There are chapters on complexes with weakly coordinated and therefore easily displaced ligands, low-valent complexes that undergo oxidative-addition reactions, substituted metal carbonyl complexes, nucleophilic metal carbonyl anions, transition metal clusters, a variety of cyclopentadienyl complexes, lanthanide and actinide complexes, and a range of other useful ligands and complexes. 

A very important class of organometallic compounds is complexes of transition metals with carbonyl (CO) ligands (see examples in Tables S3.13) [228-231]. The coordination number in these complexes is determined by the FAN mle, hence the stable complexes are tetrahedral Ni(CO)4 and Pd(CO)4, trigonal-bipyramidal [Mn(CO)5] andFe(CO)s, octahedral Cr(CO)e, Mo(CO)6 and W(CO)6. Formally CO is an inorganic ligand, the bond in it is shorter (1.128 A in the gas phase) than in CO2 (1.160 A) and is nearly triple (C O) in character. Usually CO coordinates with metal in a linear fashion which can be formally described by the valence-bond scheme M=C=0. However, metal carbonyls are typical k complexes in their... 

Carbon monoxide [630-08-0] (qv), CO, the most important 7T-acceptor ligand, forms a host of neutral, anionic, and cationic transition-metal complexes. There is at least one known type of carbonyl derivative for every transition metal, as well as evidence supporting the existence of the carbonyls of some lanthanides (qv) and actinides (1) (see AcTINIDES AND THANSACTINIDES COORDINATION COMPOUNDS). 

Because transition metals even in a finely-divided state do not readily combine with CO, various metal salts have been used to synthesize metal carbonyls. Metal salts almost always contain the metal in a higher oxidation state than the resulting carbonyl complex. Therefore, most metal carbonyls result from the reduction of the metal in the starting material. Such a process has been referred to as reductive carbonylation. Although detailed mechanistic studies ate lacking, the process probably proceeds through stepwise reduction of the metal with simultaneous coordination of CO (90). 

Polymerization of olefins such as styrene is promoted by acid or base or sodium catalysts, and polyethylene is made with homogeneous peroxides. Condensation polymerization is catalyzed by acid-type catalysts such as metal oxides and sulfonic acids. Addition polymerization is used mainly for olefins, diolefins, and some carbonyl compounds. For these processes, initiators are coordination compounds such as Ziegler-type catalysts, of which halides of transition metals Ti, V, Mo, and W are important examples. 

The primary photochemical of transition metal carbonyls [Me(CO)n] involves the scission of carbon monoxide (CO) and the formation of coordinated unsaturated species ... 

Two commonly used synthetic methodologies for the synthesis of transition metal complexes with substituted cyclopentadienyl ligands are important. One is based on the functionalization at the ring periphery of Cp or Cp metal complexes and the other consists of the classical reaction of a suitable substituted cyclopentadienyl anion equivalent and a transition metal halide or carbonyl complex. However, a third strategy of creating a specifically substituted cyclopentadienyl ligand from smaller carbon units such as alkylidynes and alkynes within the coordination sphere is emerging and will probably find wider application [22]. 

Liicke et al. have prepared other phosphinated POSS compounds Tg[(CH2)2-PMe2]8 and Tg[(CH2)3-PMe2]8 by treating T8[CH = CH2]8 or T8[CH2-CH = CH2]8 with H-PMe2 under UV irradiation. The former compound has shown to have good coordination properties to carbonyl transition metal complexes such as CpMn(CO)3 (Table 15). 

Whereas Cu and Ag form complexes with derivatives of transition-metal carbonyls in which the Cu or Ag are 4 coordinated in both the reactant and in the final product, many analogous Au complexes exhibit only 2 coordination. For example, the simple Au complex Ph3PAuCI reacts with transition-metal carbonyl anions in THF to give complexes with transition-metal to Au bonds, e.g. ... 

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