Triosmium clusters containing the ligands CNH2, NCHCN, and NCMeCN derived from cyanide ion, cyanogen, and acetonitrile

Abstract

The addition of cyanide ion to [Os₃H₂(CO)₁₀] gives [Os₃H₂(CN)(CO)₁₀]^– as four isomers in solution. Subsequent protonation at nitrogen leads via intermediates to the aminomethylidyne complex [Os₃H(µ-CNH₂)(CO)₁₀], the characterisation of which was assisted by the synthesis of the corresponding ¹³CNH₂, C¹⁵NH₂, and deuteriated analogues. Hydrogen exchange at the CNH₂ ligand is slow in neutral solution but is both acid- and base-catalysed. Rather than displacing acetonitrile from [Os₃H(CO)₁₀(MeCN)(PMe₂Ph)]PF₆, cyanide ion adds at MeCN to give two main isomers of [Os₃H (NCMeCN)(CO)₉(PMe₂Ph)]. Related complexes [Os₃H(NCHCN)(CO)₉L](L = CO or PMe₂Ph) were obtained by reaction of [Os₃H₂(CO)₉L] with cyanogen (C₂N₂) at room temperature. Rotation about the CN bonds in the iminyl complexes is sufficiently slow to allow the separation of isomers when L = PMe₂Ph. The isomeric form [Os₃H(NHCCN)(CO)₁₀] was also obtained.