INVESTIGATION OF THE TRANS INFLUENCE IN TRANSITION-METAL NITRIDE COMPLEXES

Approximate density functional theory calculations have been used to investigate the trans influence in five- and six-co-ordinate transition-metal nitride complexes. The geometries of [OsNX(4)](-) (X = Cl, Me or SMe) and [OsNCl5](2-) were optimized in the C-4v point group, The agreement between calculated and experimental geometric parameters is very good. By employing the transition-state method the relative effects of steric and electronic factors on the trans influence in these complexes was quantitatively assessed. It is found that the electronic stabilization is greater than the steric stabilization for five- and six-co-ordinate complexes. The origin of the electronic stabilization was identified. The diverse reactivities of [OsNX(4)](-) may be rationalized by a comparison of the frontier orbitals of these complexes. The analogous nitrosyl complex [Ru(NO)Cl-5](2-) does not exhibit a trans influence on the chloride trans to the nitrosyl group. This has been accounted for by considering the electronic structure of this complex.