Synthesis and reactivity of trinuclear osmium and dinuclear and trinuclear ruthenium compounds derived from hydroxyalkynes

3-Hydroxy-3-methylbut-1-yne (HCCCMe2OH) reacts with [Ru3(CO)12] to give [Ru3H(CO)9(CCCMe2OH)] in very low yield as already described, but we can now report that the main products are isomeric compounds with empirical formula [Ru2(CO)6(alkyne)2], which contain ruthenacyclopentadiene groups, and substituted benzenes formed by oligomerisation of three alkyne molecules. Much better yields of [Os3H(CO)9(C2CMe2OH)] are obtained in a similar way with no evidence for alkyne trimerisation or complex dimer formation. The complex [Os3H2(CO)10] reacts at room temperature with HC2CMe2OH to give [Os3(CO)10(HC2CMe2OH)] and [Os3H(Co)10(CHCHCMe2OH)]. The dynamic n.m.r. behaviour of the first of these and the thermal decarbonylations of both are described. The 1H n.m.r. spectra of cationic clusters formed by hydroxide-ion loss in acidic solution are reported and the involvement of such cations in substitution and dehydration reactions of the η3 ligands.