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

The cyclometalated tantalum­(V) terminal hydride complex {ArNC­(Me)­CHC­(Me)­N­[2-(CHMeCH₂)-6-ⁱPr-C₆H₃]}­(η²-N­(Xyl)­CH)­Ta­(N^tBu) 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.