Molecular and electronic structures of six-coordinate chloro-oxo-metalate complexes of V, Nb, Ta, Mo, and W

The molecular and electronic structures of anionic [MOnCl6-n] (n = 1-3) complexes of V, Nb, Ta, Mo and W have been investigated using density-functional methods. Calculated structural parameters, including geometries and vibrational frequencies, are in good agreement with reported experimental data. A detailed bonding analysis is presented, and the properties of relevance to modelling polyoxoanion chemistry are explored and discussed. Structural trans-influence phenomena have been observed in all species studied. A combined analysis based on Mulliken-Mayer population methods and geometrical and bonding-energy data, supports the idea that both electronic and electrostatic factors are involved in the trans influence. Valuable insight into the redox properties of mono-oxo and cis di-oxo complexes, and the connection with polyoxometalates, has been gained by probing the nature of frontier orbitals. In general, bonding interactions possess metal-d and ligand-p character, and are strongly covalent in M-O bonds, and from moderately to largely ionic in M-Cl bonds.