Theoretical studies on tetrahedral oxoanions MO4 n− (n=2, 3, 4; M=Cr, Mo, W)

The structure and bonding in MO4 n− (n=2, 3, 4; M=Cr, Mo, W) tetrahedral oxoanions have been investigated using density-functional methods. Good computational-experimental agreement for the geometrical parameters of the known species has been obtained which allowed the prediction of the cited parameters for those species that have not yet been isolated. The molecular-orbital analysis indicates that the chemical bonds mainly have d functions of the metal and p functions of oxygen. The electron affinities for the process MO4 n− + 1e → MO4 (n + 1)− have also been calculated and their importance in relation with the preparation of the oxoanions MO4 n− (M=Mo, W; n=3, 4) not reported in the bibliography is discussed. Comparative studies of the electronic structures of oxoanions allow to explain their reactivities against nucleophilic and electrophilic attacks. The vibrational frequencies have been calculated and compared with the experimental values and the different relationships between the symmetric-stretching and antisymmetric-bending frequencies allow to confirm the assignations of the calculated spectra.