Δ²- and Δ³-Azaosmetine Complexes as Intermediates in the Stoichiometric Imination of Phenylacetylene with Oximes

Complexes [Os{(E)-CHCHPh}Cl(NCR₂)(PⁱPr₃)₂][CF₃SO₃] [CR₂ = CMe₂ (1), (2)] react with carbon monoxide to give the Δ²-1,2-azaosmetine derivatives [CR₂ = CMe₂ (3), (4)], as a result of the coordination of carbon monoxide to the osmium atoms of 1 and 2 and the carbon−nitrogen coupling between the styryl and azavinylidene ligands. The structure of 3 in the solid state has been determined by an X-ray diffraction study. Complexes 3 and 4 can be deprotonated with MeLi to give the Δ³-1,2-azaosmetine compounds [CR₂ = CMe₂ (5), (6)], which react with molecular hydrogen to afford the 2-aza-1,3-butadienes CH₂C(Ph)NCR₂ [CR₂ = CMe₂ (7), (8)] and OsH₂(η²-H₂)(CO)(PⁱPr₃)₂. The carbonylation of the cations of 3 and 4 leads to [Os{(Z)-CHC(Ph)NHCR₂}Cl(CO)₂(PⁱPr₃)₂]⁺ [CR₂ = CMe₂ (9), (10)]. The [BF₄]^- salts of 9 and 10 have been obtained by carbonylation of 5 and 6 and subsequent protonation of the resulting η¹-azabutadiene intermediates Os{(Z)-CHC(Ph)NCR₂}Cl(CO)₂(PⁱPr₃)₂ [CR₂ = CMe₂ (11), (12)]. The structure of the [BF₄]^- salt of 10 in the solid state has also been determined by an X-ray diffraction study.