1. -Bonded Cationic Ligands as Catalysts and Precursors
Richard A. Kemp, Department of Chemistry and Chemical Biology, University of New Mexico
Ligands are the primary components of the synthetic chemist’s toolkit. All commonly-used -ligands are either neutrally-charged or anionic. To our knowledge, the only cationic ligands that react with metals species do so in
a -fashion, with examples being [NO]+, phosphenium cations [(R2N)2P]+, and triazolium cations [C2N3R4]+. We are interested in a novel class of as-yet unprepared ligands - 6-electron containing cationic ligands that will -bond to metals much like well-known neutral and anionic analogues. Target molecules will rely on p=p bonding to stabilize the cationic center. DFT calculations have shown a net attraction between species such as [(R2N)3C]+ or [(R2P)3C]+
and metal fragments, with a planar central C cation symmetrically-bound to a M(CO)3 moiety. Current effort is centered around synthesizing the cationic precursors by hydride abstraction; however, we are seeing fragmentation of the precursor (R2P)3CH species under acidic conditions. Alongside this effort we are preparing precursors with better leaving groups, such as halides. Lastly, we are also examining “pre-coordinated” [(R2P)3CH]M(CO)3 complexes and their hydride removal products in order to determine the net stability of the {[(R2P)3C]M(CO)3}+ species.