Synthesis, X-ray structural and spectroscopic study of new silyl-substituted triosmium clusters

Abstract The 2-pyridyldimethylsilane, 2-(CH 3 ) 2 SiHC 5 H 4 N LH reacts with Os 3 (μ-H) 2 (CO) 10 ] to afford the novel cluster [Os 3 (μ-H) 2 (CO) 10 L 2 ] 1 in which each of the ligands L has been shown from single crystal X-ray diffraction study to bond to one osmium atom through the silicon atom only. In addition, several silyl-substituted triosmium clusters of general formula [Os 3 (μ-H)(CO) 11 {2BrC 6 H 4 CH 2 Si(CH 3 ) 2 n H n }] ( n = 0, 2A, 1, 2B; 2, 2C), Os 3 (μ-H)CO) 10 (CH 3 CN){2-BrC 6 H 4 CH 2 Si(CH 3 ) 2- n Hn }] ( n = 0, 3A ; 1, 3B ) have been synthesized from the reactions of the silane derivatives BrC 6 H 4 CH 2 Si(CH 3 ) 3 - m H m [ m = 1, I ; 2, II ; 3, III ] with the activated clusters [Os 3 (CO) 11 CH 3 CN] and Os 3 (CO) 10 (CH 3 CN) 2 ], respectively. The acetonitrile molecule in 3A is readily substituted by a triphenylphosphine molecule to yield Os 3 (μ-H)(CO) 10 (Ph 3 P){2-BrC 6 H 4 CH 2 Si(CH 3 ) 2 })] ( 4 ). Reaction of [Os 3 (μ-H) 2 (CO) 10 ] with 2-BrC 6 H 4 Si(CH 3 ) 2 H affords the cluster [Os 3 (μ-H) 3 (CO) 9 {2-BrC 6 H 4 CH 2 Si(CH 3 ) 2 }] ( 5 ). In the case of 3A the silane moiety bonds to an osmium atom at a position equatorial to the OS 3 triangle while the acetonitrile molecule takes up an axial position. The molecular structure of 4 contains both the silane and the triphenylphosphine moieties at the terminal, equatorial positions on two separate osmium atoms. The behaviour under high performance liquid chromatography of these clusters has been determined and correlated with the nature of the ligands and with the molecular weights and sizes of the clusters.