Chemistry of polynuclear compounds. Part XXII. Protonation of triosmium dodecacarbonyl and some related compounds

Abstract

Dodecacarbonyltriosmium dissolves in cold concentrated sulphuric acid to give a solution containing the hydridospecies [HOs₃(CO)₁₂]⁺. On heating the solution at 100° this protonated species is converted first into a second hydrido-species (not characterised) and finally [HOs(CO)₅]⁺ which has also been obtained by the protonation of osmium pentacarbonyl in concentrated sulphuric acid. Sulphuric acid solutions of tertiary phosphine-substituted derivatives of [Os₃(CO)₁₂] have been shown to contain dihydrido-species of the type [H₂Os₃(CO)_12-xL_x]²⁺(x= 1–3; L = PEt₃ or PMePh₂) and from these solutions have been isolated the salts [H₂Os₃(CO)₉(PEt₃)₃](PF₆)₂ and [HOs₃(CO)₉L₃]PF₆(L = PEt₃ or PMePh₂). The latter exists in two forms, one yellow and one orange. There is some evidence that the yellow form may be an equimolar mixture of isomers. The structures of these complexes are discussed and shown, unambiguously in certain cases, to contain bridging hydrido-ligands.