Synthesis and structure of [(OC)₄Os(PbMe₂)]₂ and some derivatives of the type Os₂(CO)₇(SnMe₂)₂(L)

The complexes [(OC)₄Os(PbMe₂)]₂ (3) and [(OC)₄OsSnBu₂′]₂ (4) have been prepared from the reaction of Na₂[Os(CO)₄] with Me₂PbCl₂ and Bu₂′,SnCl₂, respectively, in THF and their X-ray crystal structures determined. The red derivative, 3, was light-sensitive in solution. The reactions of [(OC)₄ Os(SnMe₂)]₂ (2), or its decarbonylated derivative [Os₃(CO)₇(SnMe₂)₂]₂ (7), with olefins or phosphorus donor ligands have also been investigated, and the structures of two derivatives, viz. [Os₂(CO)₇(SnMe₂)₂(C ₂H₄)] (5a) and [Os₂(CO)₇(SnMe₂)₂(PMe₃)] (6a), have been determined; the noncarbonyl ligand occupies an equatorial site in each case. The X-ray crystal structures of all these compounds, like those of [(OC)₄Os(EMe₂)]₂ (E = Ge (1), Sn (2)) which have been reported previously, show leaning of the axial carbonyl ligands toward the metal tetracycle, i.e., an "umbrella" effect. Crystallographic data for compound 3: space group, P2₁/a; a = 13.4404(13) Å, b = 10.7494(14) Å, c = 14.8967(18) Å, β = 98.204(9)°, R = 0.035, 1983 observed reflections. For compound 4: space group, P1̄ a = 9.016(1) A, b = 9.370(1), c = 11.334(1) A, α = 103.67(1)°, β = 100.30(1)°, γ = 115.03(1)°, R = 0.046, 2026 observed reflections. For compound 5a: space group, P1̄ a = 9.2933(11) A, b = 9.7181(3), c = 12.2508(15) A, α = 89.21(1)°, β = 87.61 (1)° γ = 86.13(1)°, R = 0.038, 2770 observed reflections. For compound 6a: space group P1̄ a = 8.7244(9) A, b = 10.9318(6), c = 13.2560(13) A, α = 87.815(6)°, β = 83.655(8)°, γ = 82.343(6)°, R = 0.030, 3497 observed reflections.