Reversible C-C bond cleavage and interconversion of the resulting hydrocarbyl ligands on butterfly frameworks derived from acetylide complexes Cp*WOs3(mu(4)-CCR)(CO)(11) (R=Ph, Bu-n, CH2OMe, CH2OPh)

Combination of mononuclear complexes Cp*W(CO)(3)(CCR) (Cp* = C5Me5; R = Ph, Bu-n, CH2OMe, CH2OPh) with the triosmium cluster Os-3(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), Bu-n (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 la furnishes the carbido-alkylidyne cluster Cp*WOs3(mu(4)-C)(mu-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(mu(4)-C)(mu-H)(mu-CCHR')(CO)(9) (R' = Pr-n (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(mu(4)-C)(mu-H)(2)(mu-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(mu-H)(2)(CCCH2OMe)(CO)(10) (11) and the carbido-allkylidyne cluster Cp*WOs3(mu(4)-C)(mu-H)(2)(mu-CCH2OMe)(CO)(9) (13) subsequently. The acetylide cluster II converts to the tetrahedral alkylidyne complex Cp*WOs3(mu(3)-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(mu(4)-C)(mu-H)(2)(mu-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.