Chemistry of polynuclear compounds. Part XXI. Cationic hydridocarbonyl complexes of osmium

Abstract

The complex [HOs₃(CO)₁₀(SPh)] readily dissolves in concentrated sulphuric acid to produce the cationic hydrido-species [H₂Os₃(CO)₁₀(SPh)]⁺(α-form). In the n.m.r. spectrum two resonances are observed in the high-field region and on this basis the hydrido-ligands are considered to be nonequivalent. On heating the solution at 100 °C for 1 h a new isomer is produced (β-from). The α-form does not undergo proton exchange with sulphuric acid but there is exchange of hydrogen between the two nonequivalent sites. Reaction of HOs₃(CO)₁₀(SPh) with triethylphosphine produces three products which could be isolated,viz. [HOs₃(CO)₉(PEt₃)(SPh)] and [HOs₃(CO)₈(PEt₃)₂(SPh)](two isomers), together with products of further substitution. With methyldiphenylphosphine similar products were observed but only [HOs₃(CO)₉(PMePh₂)(SPh)] in two isomeric forms was isolated. Protonation of these derivatives occurs in sulphuric acid to give e.g.[H₂Os₃(CO)₉L(SPh)]⁺(L = PEt₃ or PMePh₂) and [H₂Os₃(CO)₈(PEt₃)₂(SPh)]⁺ which could be isolated as hexafluorophosphate salts; their possible structures are discussed. Evidence for the doubly protonated species [H₃Os₃(CO)₈(PEt₃)₂(SPh)]²⁺ is also given.