High-Spin Imido Cobalt Complexes with Imidyl Radical Character*.

We report on the synthesis of a variety of trigonal imido cobalt complexes [Co(NAryl)L ] , (L=N(Dipp)SiMe ), Dipp=2,6-diisopropylphenyl) with very long Co-N bonds of around 1.75 Å. Their electronic structure was interrogated using a variety of physical and spectroscopic methods such as EPR or X-Ray absorption spectroscopy which leads to their description as highly unusual imidyl cobalt complexes. Computational analyses corroborate these findings and further reveal that the high-spin state is responsible for the imidyl character. Exchange of the Dipp substituent on the imide by the smaller mesityl function (2,4,6-trimethylphenyl) effectuates the unexpected Me Si shift from the ancillary ligand set to the imidyl nitrogen, revealing a highly reactive, nucleophilic character of the imidyl unit.