In this project supported by the Inorganic, Bioinorganic and Organometallic Chemistry Program, Joseph M. O'Connor of the University of California, San Diego will continue studies in the area of organometallic research at the interface of metallacycle and carbene chemistry. This research directly impinges on the role of metal carbenes in alkene metathesis, alkene and alkyne polymerization, cyclopropanation chemistry and an impressive array of synthetic organic methodology. The proposed research has its focus on iridium, rhodium and cobalt compounds and the development of new carbene coupling reactions wherein ring-expanded metallacycles of the above metals and ultimately four- and five-membered carbocycles would be accessible. In addition to the synthetic studies, structural and mechanistic studies will also be carried out.