The synthesis and NH activation of trinuclear osmium alkylidenimine complexes. The molecular structure of Os₃(CO)₁₁[NHC(CH₂)₅].

Trinuclear osmium alkylidenimine complexes of the type Os₃(CO)₁₁(NHCR₂) were synthesized by condensation of the ammonia complex Os₃(CO)₁₁(NH₃) with ketones. The structure of the cyclohexylidenimine cluster Os₃(CO)₁₁[NHC(CH₂)₅] was determined by a single X-ray structure analysis. The complex cyrstallizes in space group P1 with a = 8.277(3), b = 11.746(4), c = 12.951(4) Å, α = 98.22(2), β = 95.25(2), γ = 113.81(21)°, Z = 2. The structure was refined to R = 0.047 for 3596 observed diffractometer data. In the solid state the osmium atoms define an isosceles triangle with the alkylidenimine ligand in an axial position. The N atom has a planar coordination geometry and the six-membered cyclohexylidene ring adopts the chair conformation. Upon heating, the NH bond of the alkylidene ligand in Os₃(CO)₁₁(NHCR₂) is activated, and the hydrogen atom transferred to the metal frame, affording alkylidenimido clu sters of the type OS₃(CO)₁₀(μ-H)(μ-NCR₂).