Syntheses, structures and chemistry of the high-nuclearity ruthenium hydrido cluster anions [Ru₁₀H₂(CO)₂₅]^2- and [Ru₁₁H(CO)₂₇]^3-

Thermolysis of [Ru₃(CO)₁₂] in ethanol yielded the decanuclear hydridoruthenium cluster dianion [Ru₁₀H₂(CO)₂₅]^2- 1. When a mixture of methanol and water is employed as thermolysis solvent the undecaruthenium hydridoruthenium trianion [Ru₁₁H(CO)₂₇]^3- 2 is also formed. Crystal structure analysis of 1 as its [N(PPh₃)₂]⁺ salt and 2 as its [NEt₃(CH₂Ph)]⁺ salt showed their metal core structures to be related, 2 being a square-faced capped congener of 1. Cluster 2 was alternatively formed in near-quantitative yields when [Ru₃(CO)₁₂] was thermolysed in acetonitrile containing traces of water for several days. It was not possible to locate the hydride ligands in the structures by potential-energy-minimisation calculations, but strong signals were seen in the ¹H NMR spectra at δ - 14.2 (s, 2 H) for 1 and at -5.47 (s, 1 H) for 2. On treatment of 1 and 2 with [Au(PPh₃)Cl] in the presence of TlPF₆, 1 showed no reactivity, but 2 reacted smoothly adding one [Au(PPh₃)]⁺ moiety and giving a product characterised as [Ru₁₁H(CO)₂₇{Au(PPh₃)}]^2- 3. The structural relationships between the known high-nuclearity ruthenium hydrido carbonyl clusters are discussed, and their implications for a possible cluster build-up sequence considered.