Synthesis of tetranuclear heterometallic cluster complexes via condensation of triosmium alkyne complexes OS₃(CO)₁₀(C₂R₂), R = Tol and Me, and mononuclear tungsten acetylide complexes LW(CO)₃C≡CR′, L = Cp and Cp*, R′ = Ph and ^tBu

Condensation of triosmium alkyne complexes OS₃(CO)_1O(C₂R₂), R = Tol and Me, with mononuclear tungsten acetylide complexes LW(CO)₃C≡CR′, L = Cp and Cp*, R′ = Ph and ^tBu generated six WOS₃ cluster complexes via 1:1 combination of the starting materials. The tetrahedral complexes LWOs₃(CO)₉[CC(R′)C(R)C(R)] (1) formed via coupling of the ligated alkyne with the β-carbon of the acetylide ligand were observed in all cases studied. The planar rhomboidal cluster CpWOS₃(CO)_1O[C(Me)C(Me)CC(Ph)] (2), generated via coupling of the ligated alkyne with the α-carbon of the acetylide ligand, was isolated only from the reaction between Os₃(CO)₁₀(C₂Me₂) and CpW(CO)₃C≡CPh. On thermolysis, complex 2 loses one CO to afford CpWOs₃(CO)₁₀(CO)₉(μ-H)[CMeC-MeCC(μ₂-η²-C₆H₄)] (7) via ortho-metallation of the phenyl substituent and CpWOs₃(CO)₉(CCMe-CMe)(μ₃-CPh) (3a) via cleavage of the C-C bond of the ligated C₄ hydrocarbon fragment, confirming that the alkylidyne and the coordinated C₃ hydrocarbon ligands in 3a were generated via alkyne-acetylide coupling followed by cleavage of a C-C bond. For the reaction between Os₃(CO)₁₀(C₂Me₂) and Cp*W(CO)₃C≡CPh, in addition to the expected complexes 1e and 3e (L = Cp*; R′= Ph), we observed the formation of three new complexes Cp*WOs₃-(CO)₉(C₂Me₂μ₃-CCPh) (4), Cp*WOs₃-(CO)₉(C₂Me₂)(μ₄-CCPh) (5) and Cp*WOs₃(CO)₉(μ₃-CPh)[CC(Me)C(Me)CO] (6). The X-ray structural determination reveals that the butyne and acetylide ligands in butterfly complexes 4 and 5 remain as two uncoupled entities. Complexes 4 and 5 are not the precursors for the formation of other cluster complexes, as pyrolysis of these two complexes in refluxing toluene failed to afford substantial amount of butyne-acetylide coupling products. Finally, the tetrahedral complex 6 possesses two triply bridging alkylidyne ligands and a triply bridging CO ligand; the formation of alkylidyne ligands occurs via a C-C bond scission of a ligated CMeCMeCCPh fragment, except that a CO ligand inserts into the linkage between the butyne fragment and the transition metal. ...