Kinetic and labeling studies of alkane elimination from cis-Os (CO),(H) R have shown that the ratedetermining step is isomerization of cis-Os (CO),(H) R to a reactive intermediate (probably an acyl hydride); this intermediate can then react either with unisomerized cis-Os (CO),(H) R to give intermolecular RH elimination (and HOs (CO), Os (CO), R) or with another nucleophile L to give intramolecular RH elimination (and Os (CO), L). The ck-Os (CO),(H) ...