Electrospray mass spectrometry of [Ru4(η6-C6H6)4(OH)4]4+: first direct evidence for the persistence of the cubane unit in solution and its role as a precatalyst in the hydrogenation of benzene

The electrospray ionisation mass spectrum of [Ru4(η6-C6H6)4(OH)4]4+ shows that the main species present in aqueous solution are based on the intact cubane tetramer and the dimer [Ru2(η6-C6H6)2(OH)2]2+. The latter species is an active benzene hydrogenation catalyst.