Systematic studies of the influence of electronegative X (X = F and Cl) substituents on the structure of the Mn–H–Si unit and the strength of the Mn⋯([formula omitted]-SiH) [formula omitted] interaction in Cp(OC)2Mn[[formula omitted]-H(SiH3−nXn)] ([formula omitted]) complexes

Abstract

Results of systematic studies of the influence of electronegative X (X=F and Cl) substituents at the SiR3 moiety on the structure of the Mn–H–Si unit and the strength of the Mn⋯(η2-SiH) σ interaction in Cp(OC)2Mn[η2-H(SiH3−nXn)] (n=0–3) complexes are presented. It is shown that the length of the η2-SiH bond depends on the position of the halogen atom at Si, the number of halogens, and the type of the halogen. Considering position of the halogen atom, it is shown that the Si⋯H distance results from two opposite effects: a slight η2-SiH bond shortening due to the presence of a halogen atom at any position at –SiH3−nXn and the more pronounced bond elongation resulting from the trans halogen atom. In order to explain the influence of an electronegative atom X on the length of the η2-SiH bond in Cp(OC)2Mn[η2-H(SiH3−nXn)] complexes a new model is proposed. It is based on a marriage of the idea of an inductive effect caused by a presence of a halogen atom being at any position relative to the η2-SiH bond and the probable ‘trans effect’ if the halogen X is present at the position trans. This model is shown to be in accord with all presented changes of the η2-SiH bond length. The influence of halogens substituted at Si on the Mn–H distance is negligible. On the contrary, one observes considerable influence on the Mn⋯Si distance.