This project in the Inorganic, Bioinorganic and Organometallic chemistry Program is in the area of transition metal organometallic chemistry. The results of the project will enhance fundamental knowledge in an area critical to the development of new catalysts for chemical synthesis and hydrocarbon conversion. The foci of the research are the monoimido alkylidene chemistry of Mo and W and the chemistry of alkylidyne, alkylidene and imido complexes of Re. Mechanistic studies will be carried out on olefin metathesis reactions involving Mo and W complexes of the type M(CHR')(NAr)(OR)2, where Ar=2,6-diisopropylphenyl. The goal of these experiments will be to sort out the role of trigonal bipyramidal metallacyclobutane complexes versus square pyramidal metallacyclobutane complexes, and how precisely olefin metathesis activity is controlled by varying the nature of the OR group. Another goal will be to develop a practical synthetic route to molybdenum catalysts, since molybdenum is more tolerant of functional groups than is tungsten. A third goal will be to extend what has been learned to rhenium, i.e.,to prepare rhenium acetylene and olefin metathesis catalysts whose activity can be controlled by the choice of alkoxide ligands, in part because rhenium is likely to be the most tolerant of these metals toward functional groups. The behavior of monoimido alkylidyne complexes of the type Re(CR')(NAr)(OR)2 as acetylene metathesis catalysts will be investigated also, since at least one related complex is known already to be an active catalyst for internal acetylenes. The organometallic chemistry of Re(VII) in general will be developed as routes to such compounds become available.
