Reversible C–C Bond Cleavage and Interconversion of the Resulting Hydrocarbyl Ligands on Butterfly Frameworks Derived from Acetylide Complexes Cp*WOs₃(μ₄-CCR)(CO)₁₁ (R = Ph, ⁿBu, CH₂OMe, CH₂OPh)

Combination of mononuclear complexes Cp*W(CO)₃(CCR) (Cp* = C₅Me₅; R = Ph, ⁿBu, CH₂OMe, CH₂OPh) with the triosmium cluster Os₃(CO)₁₀(NCMe)₂ in toluene affords two isomeric acetylide cluster compounds a and b, which possess the formula Cp*WOs₃(CCR)(CO)₁₁ (R = Ph (1), ⁿBu (2), CH₂OMe (3), CH₂OPh (4)). Isomers a and b undergo reversible interconversion by relocating the Cp*W(CO)₂ fragment between the hinge and wingtip positions upon heating in solution. Their reactivities vs the substituents on the acetylide ligand are also investigated and compared. Thus, thermolysis of 1a furnishes the carbido–alkylidyne cluster Cp*WOs₃(μ₄-C)(μ-CPh)(CO)₁₀ (5) through reversible scission of the C–C bond induced by elimination of CO. By contrast, heating of 2 or 3 gives an isomeric mixture of the carbido–vinylidene clusters Cp*WOs₃(μ₄-C)(μ-H)(μ-CCHR′)(CO)₉ (R′ = ⁿPr (6), OMe (7)) through a subsequent C–H activation. The CH₂OPh isomers 4 readily eliminate two CO ligands to give two isomeric carbido–benzofuryl clusters Cp*WOs₃(μ₄-C)(μ-H)₂(μ-C₈H₆O)-(CO)₉ (9 and 10), in which the furyl fragments are produced through subsequent orthometalation involving the phenyl group, C–C bond formation, and H migration. Hydrogenation of 3 produces the dihydrido–acetylide cluster Cp*WOs₃(μ-H)₂(CCCH₂OMe)(CO)₁₀ (11) and the carbido–alkylidyne cluster Cp*WOs₃(μ₄-C)(μ-H)₂(μ-CCH₂OMe)(CO)₉ (13) subsequently. The acetylide cluster 11 converts to the tetrahedral alkylidyne complex Cp*WOs₃(μ₃-CCH₂CH₂OMe)(CO)₁₁ (12) via addition of a CO ligand, whereas the alkylidyne cluster 13 isomerizes upon further heating in solution, giving the alkenyl cluster Cp*WOs₃(μ₄-C)(μ-H)₂(μ-CHCHOMe)(CO)₉ (14) via a 1,2-H shift. Spectroscopic data, X-ray structural analyses, and the possible mechanism leading to the interconversions are presented.