Ta(CNDipp)₆: An Isocyanide Analogue of Hexacarbonyltantalum(0)

Hexakis(2,6-diisopropylphenylisocyanide)tantalum is the first isocyanide analogue of the highly unstable Ta(CO)₆ and represents the only well-defined zerovalent tantalum complex to be prepared by conventional laboratory methods. Two prior examples of homoleptic Ta⁰ complexes are known, Ta(benzene)₂ and Ta(dmpe)₃, dmpe=1,2-bis(dimethylphosphano)ethane, but these have only been accessed via ligand co-condensation with tantalum vapor in a sophisticated metal-atom reactor. Consistent with its 17-electron nature, Ta(CNDipp)₆ undergoes facile one-electron oxidation, reduction, or disproportionation reactions. In this sense, it qualitatively resembles V(CO)₆, the only paramagnetic homoleptic metal carbonyl isolable under ambient conditions.