SYNTHESIS AND PROTONATION OF AN OS-3(MU-H)(CO)(10)(MU-SIGMA,ETA(2)-C-CCME2OME) CLUSTER

Triosmium cluster Os-3(mu-H)(CO)(10)(mu-sigma,eta(2)-C=CCMe2OMe) (1) w as obtained by treating Os-3(mu-H)(mu-Cl)(CO)(10) with LiC=CCMe2OMe. T he reaction of cluster 1 with HBF4 . Et2O at -60 degrees C leads to th e cationic complex u-H)(CO)(10)(mu-sigma,sigma,eta(2)-C=C=CMe2)]+BF4- (2) with an allenylidene ligand. The H-1 and C-13 NMR spectra of compl ex 2 reveal the temperature dependence caused by migration of hydrocar bon and carbonyl ligands. Thermodynamic parameters were obtained for t he exchange process of the allenylidene ligand.