PREPARATION AND STRUCTURES OF MIXED SILICON-COBALT CARBONYL CLUSTERS WITH SI-H, SI-O OR SI-S BONDS

Reaction of Si2H6 with greater than or equal to 3 molar equivalents of Co-2(CO)(8) in hexane gives the closo-cluster Co-4(mu(4)-SiCo(CO)(4)) (CO)(11), while with <3 molar equivalents the partially substituted cl uster H2Si(3)Co(6)(CO)(20) is formed. An X-ray crystal structure deter mination shows the latter to be relatively open, with linked SiCo2 tri angles and retention of Si-H bonds on two of the silicon atoms. With O (SiH3)(2), Co-2(CO)(8) gives mainly the mono-silyl complex mu(4)-Si[Co -2(CO)(7)](2), together with an unstable species tentatively identifie d as O(Si[Co(CO)(4)]Co-2(CO)(7))(2). Reaction of S(SiH3)(2) with Co-2( CO)(8) gives Co-4(mu(4)-S)(2)(CO)(11) and the novel cluster SSi2Co2CO) (14); the latter was shown crystallographically to contain a Co-2(CO)( 6) unit doubly-bridged by two silicon atoms that are in turn linked by the sulphur atom. There is also a terminal Co(CO)(4) group attached t o each silicon atom. The most notable feature of this structure is an acute Si-S-Si bond angle of 70.3 degrees which leads to a very short f ormally non-bonded Si...Si distance of 2.498 Angstrom.