A theoretical evaluation of steric and electronic effects on the structure of [OsO4(NR(3))] (NR(3) equals bulky chiral alkaloid derivative) complexes

The novel theoretical scheme IMOMM, integrating ab initio and molecular mechanics contributions in a single geometry optimization process, is applied to the structural determination of different [OsO4(NR(3))] (NR(3) = bulky chiral alkaloid derivative) species closely related to active catalysts for the asymmetric dihydroxylation of olefins. Computed values compare in a satisfactory way with available X-ray data, the relationship between the Os-N distance and the nature of the NR(3) ligand being properly reproduced. The computational scheme allows the separate quantification of electronic and steric effects, as well as the identification of the specific steric repulsions responsible for the difference.