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-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 [(R 2N)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 {[(R 2P)3C]M(CO)3}+ species.
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Various
Transition Metal
Complexes
(Karsch, Issleib, Grim)
X-ray Structure of
[(Ph2P)3CH]Mo(CO)3(EtCN)
Comparison of {[(H2N)3C]Cr(CO)3}+ and
[(H2N)3CH]Cr(CO)3 by DFT
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Q uickTim e™ and a
TI FF ( Uncom pr essed) decom pr essor
ar e needed t o see t his pict ur e.
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(this proposed work...)
chelating or bridging ligands
(Selegue, Smith, Mague)