DEVELOPMENT AND MECHANISTIC STUDY OF A NEW ALDEHYDE DECARBONYLATION CATALYST

Rh2(PMe3)2(CO)2CI2 (2) has been found to catalyze the decarbonylation of aldehydes to give the corresponding alkanes. Reaction rates are comparable to those of the most active nonradical systems previously reported. A mechanistic study indicates that the turnover-limiting reaction step includes addition of the aldehydic C-H bond to an intact molecule of 2; ligand dissociation or cleavage of the chloride bridge does not occur prior to the C-H addition step. This conclusion is based on kinetic studies (d[R'H]/dt = k(obs)[2] [R'CHO]; R' = n-C11H23; k(obs) = 2.2 x 10(-4) M-1 s-1; DELTA-S double-dagger = -26 eu) and the observation of a significant kinetic isotope effect (k(RCHO/RCDO) > 1.8).