Bonding in metal carbonyls

In Nb3Cp3(CO)7 the bridging carbon monoxide is bonded to one niobium atom through carbon, and with the other two Nb atoms it forms a Tr-olefm bond (a six-electron ligand). 

bridging carbonyl groups exist in pairs  

The tendency to form carbonyls with bridging CO groups decreases with increase in atomic size of the metal. This trend is observed in groups as well as in series of the 

The metal-carbonyl group bond may be described by the following resonance structures  

In the Oh group, the n bonding and n antibonding orbitals of six CO ligands form four triply degenerate linear combinations belonging to the representations /jg, and t2n- The t2g n) and t2g(n ) orbitals may overlap with the t2g metal orbitals. Less important is the interaction of metal orbitals with the filled n orbitals of the CO group. 

---

Spectra and bonding in metal carbonyls part A, bonding. P. S. Braterman, Struct. Bonding (Berlin), 1972,10, 57-86 (110). 

Bradshaw AM, Cederbaum LS, Domcke W (1975) Ultraviolet Photoelectron Spectroscopy of Gases Adsorbed on Metal Surfaces. 24 133-170 Braterman PS (1972) Spectra and Bonding in Metal Carbonyls. Part A Bonding. 10 57-86 Braterman PS (1976) Spectra and Bonding in Metal Carbonyls. Part B Spectra and Their Interpretation. 26 1-42... 

Braterman, P. S. Spectra and Bonding in Metal Carbonyls. Part B Spectra and Their Interpretation. Vol. 26, pp. 1 2. 

Wade also extended the application of his rules to transition metal clusters the further extension by D. M. P. Mingos mainly concerns the bonding in metal carbonyl and metal phosphane clusters, i.e. organometallic compounds (Wade-Mingos rules) these are beyond the scope of this book. 

The depressed reactivity of the CO bond in metal carbonyls relative to organic carbonyls is not apparent in the case of BH3 and A1H3. For example, Masters and coworkers have observed that I B THF reduces metal acyl compounds to the corresponding alkyls, eq. 16. Although no mechanistic studies have been reported, it... 

Z. Iqbal Intra- and Inter-Molecular Bonding and Structure of Inorganic Pseudohalides with Triatomic Groupings. P.S.Braterman Spectra and Bonding in Metal Carbonyls. Part A Bonding... 

Spectra and Bonding in Metal Carbonyls The secular equations in the energy factored approximation are, for M(CO)5L,... 

---