Phosphinobenzyl- and aryl-silanes and their triosmium cluster carbonyl derivatives

Abstract

The Grignard reagents MgR(Br)(R = C₆H₄CH₂SiMe₂H-o or C₆H₄CH₂SiMeH₂-o) have been found to undergo unusual reactions with Ph₂PCl to afford o-Ph₂PC₆H₄CH₂SiMe₂H I and o-HMe₂SiC₆H₄CH₂PPh₂II and o-Ph₂PC₆H₄CH₂SiMeH₂III and o-H₂MeSiC₆H₄PPh₂IV respectively. Reactions of the respective bidentate ligands I, II, III and IV with [Os₃(CO)₁₀(MeCN)₂] gave the novel triosmium cluster [Os₃(µ-H)(CO)₁₀(L–L)]1, 2, 3 and 4 involving cleavage of one Si–H bond. Similar reactions of ligands II and IV with [Os₃(µ-H)₂(CO)₁₀] afforded two new clusters [Os₃(µ-H)₃(CO)₈(L–L)]5 and 6 respectively. The structures of 1, 2, 4 and 5 have been determined by single-crystal X-ray diffraction techniques. In each case, the ligand assumes a chelating mode across the long edge of the osmium triangle which is also bridged by a hydride. The high-performance liquid chromatographic behaviour of these clusters has also been determined and correlated with the size and nature of the ligands.