STABLE SILYLENES AS LIGANDS IN ORGANOMETALLIC CATALYSIS

Silylenes (R2Si:), the silicon analogs to carbenes in organic chemistry, are key intermediates in numerous thermal and photochemical reactions of organosilicon compounds and hence, are extremely important in the discipline of silicon chemistry. The field of silylene research has grown dramatically since the isolation of the first room temperature stable silylene in 1994. The remarkable stability of this silylene is attributed to aromatic delocalization of the pi-electrons in its N-heterocyclic ring. Stable N-heterocyclic silylenes represent an important new class of ligands in transition metal chemistry. Preliminary studies indicate that these sterically demanding ligands behave electronically very much like triaryl phosphines. However, silylenes are less labile than phosphine ligands, which will likely result in greater thermal stability of metal-silylene complexes in comparison to analogous metal-phosphine complexes. This stability, in conjunction with the success of structurally similar N-heterocyclic carbenes as ligands in metal catalysts, invites the study of catalytic properties of silylene-metal complexes. Thus, the synthesis of stable silylenes, their incorporation into metal complexes, and the subsequent application of these complexes as catalysts in organometallic reactions will be the primary focus of this research. For example, the catalytic activity of novel silylene-based metal complexes will be explored in an attempt to improve valuable carbon-carbon bond forming transformations such as Stille and Suzuki cross-coupling reactions.

SYNTHESES OF MITOCHONDRIALLY TARGETED ANTI-OXIDANTS

Mitochondria are key-role players in modulating a variety of toxic insults, including oxidative stress. Smith et.al. (Eur. J. Biochem. 1999, 263, 709) have described the synthesis of a novel anti-oxidant compound, TPPB, a structurally modified version of Vitamin E. Due to its charged, lipophilic side-chain, TPPB accumulates in mitochondria of living cells and thus, represents a promising anti-oxidant that may have the unique ability to offer protection against oxidative damage where it is most needed (i.e. the molecule can behave as a sort of "guided missile"). The goal of this project is to synthesize a variety of derivatized anti-oxidants containing a positively charged, fat-soluble side chains and to subsequently explore their anti-oxidant properties in the mitochondria of rat primary oligodendrocyte precursors and neuronal cultures. This research is being conducted in collaboration with Dr. James Connor at Penn State University's Hershey Medical Center.