Reaction of [Os3H2(CO)(10)] with the diyne Me3SiC2C2SiMe3 and the reactivity of the products towards [Co-2(CO)(8)]: the X-ray structures of [Os-3(mu-H)(CO)(10){mu-eta(1)-eta(2)-HC2(SiMe3)C-2(SiMe3)}], [Os-3(mu-CO)(CO)(9){mu(3)-eta(2)-Me3SiC2C2SiMe3}] and [Os-3(mu-H)(CO)(9){mu(3)-eta(1):eta(2)-;mu-eta(2)-Me3SiC2C2[Co-2(CO)(6)]}]

The reaction of [Os3H2(CO)(10)] with Me3SiC2C2SiMe3 affords both [Os-3(mu-H ) (CO)(10){mu-eta(1)-eta(2)-HC2(SiMe3)C-2(SiMe3)}] (1) and [Os-3(mu-CO)(CO) (9)(mu(3)-eta(2)-Me3SiC2C2SiMe3)] (2) in good yield, 2 being favoured with an excess of diyne. In 1, one edge of the triosmium unit is bridged by the vinyl moiety of a transformed bis(trimethylsilyl)-1,4-butadiyne ligand that has undergone a hydride transfer and a 1,2-trimethylsilyl shift. Compound 2 is selectively desilylated in methanol to produce a single isomer of the known cluster [Os-3(mu-CO)(CO)(9){mu(3)-eta(2)-HC2C2SiMe3}] (3). Whereas re action of 3 with [Co-2(CO)(8)] results in the production of the previously reported cluster [Os-3{mu(3)-eta(2)-:mu-eta(2)-(Me3SiC2C2H)[Co-2(CO)6]}(mu- CO)(CO)(9)] (4) and a second product [Os-3(mu-H)(CO)(9){mu(3)-eta(1):eta(2) -;mu-eta(2)-Me3SiC2C2[Co-2(CO)(6)]}] (5), the reaction of 1 and 2 results i n recovery of the starting material or transfer of the alkyne ligand to the Co, unit. Compound 4 undergoes a transformation to 5 in visible light. All the cluster complexes have been characterized spectroscopically, and the s olid-state structures of 1, 2 and 5 have been determined by single-crystal X-ray diffraction. (C) 2000 Elsevier Science S.A. All rights reserved.