STOICHIOMETRIC AND CATALYTIC ACTIVATION OF SP(2) C-H BONDS - MOLECULAR-STRUCTURE OF OS-3(MU(3)-H)(MU(3)-(N)BUOC=CHPET2)(CO)(9) AND CATALYTIC PROPERTIES OF THIS AND RELATED OS AND RU CLUSTERS

The thermal reaction of (BuOCH)-Bu-n = CHPEt2 with Os-3(CO)(12) gives a new osmium triangular cluster, Os-3(mu-H)(mu(3) - (BuOC)-Bu-n = CHPE t2)(CO)(9) (1), which was isolated in 62% yield. The structure of 1 ha s been determined by X-ray diffraction (<P(1)over bar>, a = 12.914(3), b = 13.984(4), c = 16.375(4) Angstrom, alpha = 66.83(2), beta = 77.82 (2), gamma = 77.97(2)degrees, Z = 4, d(calc) = 2.552 g/cm(3), R = 0.03 99 for 6636 reflections). The mu(3) - (BuOC)-Bu-n = CHPEt2 in 1 acts a s a five-electron donor. It forms a sigma-bond with one Os atom and co ordinates the second and the third Os atoms of the cluster by its olef inic bond and the phosphorus atom, respectively. Both complex 1 and Os -3(mu-H)(mu-CH = CHR)(CO)(10) (R = (C6H13)-C-n, Ph) catalyze the silyl ation of terminal olefins with Et3SiH to yield the corresponding trans -triethylvinylsilanes and alkanes in moderate yield evert at ambient t emperature. The proposed mechanism of olefin silylation catalyzed by t riangular metal clusters involves the olefin C-H bond activation on th e triangular cluster core and formation of an intermediate which has a structure similar to that of cluster 1. (C) 1997 Elsevier Science S.A .