Synthesis, characterisation and reactivity of siloxyl-substituted derivatives of [Ru3(CO)12].: Crystal structure of trans-[Ru2(CO)8{Si(OSiMe3)3}2]

Thermal reactions of the bulky siloxysilanes HSi(OSiMe3,)(3) and HSiMe(OSiMe3)(2) with [Ru-3(CO)(12)] led to the formation of siloxyl-substituted triruthenium clusters. Formal replacement of one or more CO ligands from [Ru-3(CO)(12)] via oxidative addition generates [Ru3H(CO)(11){eta(1)-Si(OSiMe3)(3))}] 1, [Ru3H2(CO)(10),{eta(1)-Si(OSiMe3)(3)}(2)] 3, [Ru3H(CO)(11){eta(1)-SiMe(OSiMe3)(2)}] 4 and [Ru3H2(CO)(10){eta(1)-SiMe(OSiMe3)(2)}(2)] 6. Also formed are [Ru3H(Co)(10),{eta(2)-Si(OSiMe3)(3)}] 2 and [Ru3H(CO)(10),{eta(2)-SiMe(OSiMe3)(2)}] 5 in which a second CO molecule has been displaced from clusters 1 and 4 respectively, resulting in the formation of a dative SiO-->Ru interaction. The siloxyl-substituted compounds are thermodynamically unstable and decompose to dinuclear species, [Ru-2(Co)(8){Si(OR)(3)}(2)] and [Ru4H4,(CO)(12)] within several hours. Alternatively the dinuclear complexes can be synthesized cleanly and selectively by the photochemical reaction of [Ru-3(CO)(12)] with the appropriate silane and trans-[Ru-2(CO)(8){Si(OSiMe3)(3)}(2)] 7 has been characterised by X-ray crystallography at 193 K. The structure is strongly disordered.