American Chemical Society

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Synthesis and Redox Chemistry of a Tantalum Alkylidene Complex Bearing a Metallaimidazole Ring

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posted on 2017-08-21, 11:38 authored by Benjamin M. Kriegel, Nikolas Kaltsoyannis, Ruchira Chatterjee, Robert G. Bergman, John Arnold
The cyclometalated tantalum­(V) terminal hydride complex {ArNC­(Me)­CHC­(Me)­N­[2-(CHMeCH2)-6-iPr-C6H3]}­(η2-N­(Xyl)­CH)­Ta­(NtBu) reacts cleanly with 2 equiv of 2,6-dimethylphenyl isocyanide via migratory insertion to give a product containing a unique metallaimidazole ring. This complex can be reversibly oxidized by one electron, either electrochemically or chemically, to give a tantalum radical cation species. DFT calculations, as well as X-ray crystallographic and EPR spectroscopic data, are consistent with the electron being removed from an orbital primarily composed of Ta–C π-bonding character but also delocalized over the tantalaimidazole ring.