RETENTION OF STEREOCHEMISTRY IN THE FORMATION AND FRAGMENTATION OF DIOSMACYCLOBUTANES, AND OTHER EVIDENCE AGAINST A DIRADICAL MECHANISM

Two results argue against a diradical intermediate in the exchange of diosmacyclobutanes with free olefins. The diosmacyclobutane Os2(CO)8(m u-propene) reacts with vinylcyclopropane to give as the sole product a diosmacyclobutane bearing an intact cyclopropane ring. Repeated excha nge of trans-ethylene-1,2-d2 with the same ligand in a diosmacyclobuta ne shows >99.1% stereochemical excess per exchange half-life. These ex change reactions do not involve mononuclear olefin complexes.