PHOSPHINOBENZYL-SILANES AND ARYL-SILANES AND THEIR TRIOSMIUM CLUSTER CARBONYL DERIVATIVES

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-HMe2SiC6H4CH2PPh2 II and o-Ph2PC6H4CH2SiMeH2 III and o-H2MeSiC6H4CH4PPh2 IV respectively. Reactions of the respective bidentate ligands I, II, III and IV with [Os3(CO)10(MeCN)2] gave the novel triosmium clusters [Os3(mu-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(mu-H)2(CO)10)] afforded two new clusters [Os3(mu-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.