Characterization of Co-C bonding in dichlorovinylcobaloxime complexes

Angela D. Follett, Katherine A. McNabb, Alicia A. Peterson, Joseph D. Scanlon, Christopher J. Cramer, Kristopher McNeill

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23 Scopus citations

Abstract

This study combines theory and experiment in an examination of Co-C bonding and reductive Co-C cleavage in cobalt dichlorovinyl complexes. It is motivated by the role of dichlorovinyl complexes as intermediates in the dechlorination of trichloroethylene by cobalamin and cobalamin model complexes. A series of seven cis-1,2-dichlorovinyl(L)cobaloxime complexes were prepared (L = m- and p-substituted pyridines; cobaloxime = bis-(dimethylglyoximato)cobalt). The complexes were characterized using 1H NMR, 13C NMR, cyclic voltammetry, and X-ray crystallography. Examination of the metrical parameters of the Co-C=C unit across the series shows very little change in the C=C bond length and a slight increase in the Co-C bond length with increasing electron-donating ability of the pyridine ligand. These structural changes along with electronic structure calculations indicate that Co-C π-bonding is not important in these complexes. The stronger Co-C bonds of vinylcobaloximes compared to those of alkylcobaloximes are best explained by the higher s character at C. Changes in the reduction potential across the series indicate that the pyridine-bound form is the primary electrochemically active species. Theoretical examination of the Co-C cleavage following reduction supports the direct formation of the cis-1,2-dichlorovinyl anion and not the cis-1,2-dichlorovinyl radical.

Original languageEnglish (US)
Pages (from-to)1645-1654
Number of pages10
JournalInorganic Chemistry
Volume46
Issue number5
DOIs
StatePublished - Mar 5 2007

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