REVERSIBLE C-C BOND-CLEAVAGE AND INTERCONVERSION OF THE RESULTING HYDROCARBYL LIGANDS ON BUTTERFLY FRAMEWORKS DERIVED FROM ACETYLIDE COMPLEXES CP-ASTERISK-WOS3(MU(4)-CCR)(CO)(11) (R=PH, BU-N, CH2OME, CH2OPH)

Combination of mononuclear complexes CpW(CO)(3)(CCR) (Cp* = C5Me5; R = Ph, Bu-n, CH2OMe, CH2OPh) with the triosmium cluster Os-3(CO)(10)(NC Me)(2) in toluene affords two isomeric acetylide cluster compounds a a nd b, which possess the formula CpWOs3(CCR)(CO)(11) (R = Ph (1), Bu-n (2), CH2OMe (3), CH2OPh (4)). Isomers a and b undergo reversible inte rconversion by relocating the CpW(CO)(2) fragment between the hinge a nd wingtip positions upon heating in solution. Their reactivities vs t he substituents on the acetylide ligand are also investigated and comp ared. Thus, thermolysis of la furnishes the carbido-alkylidyne cluster CpWOs3(mu(4)-C)(mu-CPh)(CO)(10) (5) through reversible scission of t he C-C bond induced by elimination of CO. By contrast, heating of 2 or 3 gives an isomeric mixture of the carbido-vinylidene clusters CPWOs 3(mu(4)-C)(mu-H)(mu-CCHR')(CO)(9) (R' = Pr-n (6), OMe (7)) through a s ubsequent C-H activation. The CH2OPh isomers 4 readily eliminate two C O ligands to give two isomeric carbido-benzofuryl clusters CPWOs3(mu( 4)-C)(mu-H)(2)(mu-C8H6O)-(CO)(9) (9 and 10), in which the furyl fragme nts are produced through subsequent orthometalation involving the phen yl group, C-C bond formation, and H migration. Hydrogenation of 3 prod uces the dihydrido-acetylide cluster CpWOs3(mu-H)(2)(CCCH2OMe)(CO)(10 ) (11) and the carbido-allkylidyne cluster CpWOs3(mu(4)-C)(mu-H)(2)(m u-CCH2OMe)(CO)(9) (13) subsequently. The acetylide cluster II converts to the tetrahedral alkylidyne complex CpWOs3(mu(3)-CCH2CH2OMe)(CO)(1 1) (12) via addition of a CO ligand, whereas the alkylidyne cluster 13 isomerizes upon further heating in solution, giving the alkenyl clust er CpWOs3(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 mech anism leading to the interconversions are presented.