Transition metal carbonyls and

Matrix isolation studies on transition metal carbonyls and related species. J. K. Burdett, Coord. Chem. Rev., 1978, 27,1-58 (212). 

Thermochemical studies of organo-transition metal carbonyls and related compounds. J. A. Connor, Top. Curr. Chem., 1977, 71, 72-110 (122). 

Connor, J. A. Thermochemical Studies of Organo-Transition Metal Carbonyls and Related Compounds. 71, 71-110 (1977). 

The potential of the techniques described here is just beginning to be realized. Our approach is clearly well-suited to studying the photochemistry of virtually any (volatile) transition metal carbonyl and the spectroscopy of the fragments thus obtained. Kinetic data on these fragments is similarly accessible. Important areas for further research appear to be ... 

Thermochemical Studies of Organo-Transition Metal Carbonyls and Related Compounds... 

I propose to develop and apply such methods, based on ultrafast X-ray absorption spectroscopy, to study the ultrafast molecular motions of organometallics in solutions. In particular, initial studies will focus on photo-induced ligand dissociation and substitution reactions of transition metal carbonyls and related compounds in various solvent systems. 

Further examples of coordinate bonds are found in metal carbonyl complexes. Metal carbon (carbon monoxide) bond distances in a selection of (first-row) transition-metal carbonyls and transition-metal organometallics are examined in Table 5-11. As expected, Hartree-Fock models do not perform well. The 6-3IG model is clearly superior to the STO-3G and 3-2IG models (both of which lead to completely unreasonable geometries for several compounds), but still exhibits unacceptable errors. For example, the model shows markedly different lengths for the axial and equatorial bonds in iron pentacarbonyl, in contrast to experiment where they are nearly the same. Hartree-Fock models cannot be recommended. 

Table 5-11 Metal-Carbon (CO) Bond Distances in Transition-Metal Carbonyls and Organometallics... 

Bailey, D. C. Langer, S. H. Immobilised Transition-Metal Carbonyls and Related Catalysts, Chem. Rev. 1981, 81, 109-148. 

The highly covalent nature of transition metal carbonyls and their derivatives leads to the 18-electron rule being closely followed. The mononuclear species Ni(CO)4, Fe(CO)5, Ru(CO)5, Os(CO)5, Cr(CO)6, Mo(CO)6 and W(CO)6 obey this well and, if the formalized rules of electron counting are applied, so do the metal—metal bonded and carbonyl bridged species. Such compounds are therefore coordinately saturated and the normal (but by no means unique) mode of substitution is dissociative (a 16-electron valence shell being less difficult to achieve than one with 20 electrons).94... 

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