Metal-support interaction: (μ-H)(μ-OSiEt₃)Os₃(CO)₁₀, A molecular analogue of a surface complex and the computer modelled surface structures of (μ-H)(μ-OSi)Os₃(CO)₁₀ and (μ-OSi)₂Os₃(CO)₁₀

Metal-support interaction involving the surface complex formed from the reaction of silica with Os₃(CO)₁₂ at 150°C has been modelled employing computer graphics and molecular mechanics techniques. This surface complex is generally represented as (μ-H)(μ-Osi) Os₃(CO)₁₀ (I), with a surface oxygen bridging two osmium atoms. However, a second arrangement with two surface oxygens bridging the same two osmium atoms, (μ-Os)₂Os₃(CO)₁₀ (II), has also been considered. A computer model has been developed for partially hydroxylated silica surface. Employing structural parameters from model compounds, metal-support interaction of the cluster fragments (μ-H)Os₃(CO)₁₀ and Os₃(CO)₁₀ with surface oxygens to form surface complexes I and II was studied using energy minimization techniques and considering non-bonded contacts as a function of dihedral angle. The results clearly indicate that the cluster fragment Os₃(CO)₁₀ will not fit on the silica by means of a double oxygen bridge to two osmium atoms to give complex II; however, the (μ-H)Os₃(CO)₁₀ fragment will bind to selected oxygen sites of the silica without steric restraint to form complex I.