| Sumario: | Low-temperature photolysis experiments (T = 10 K) on the tripodal azido complex [(BIMPN)Co(N)] ( l) were monitored by EPR spectroscopy and support the formation of an exceedingly reactive, high-valent Co nitrido species [(BIMPN)Co (N)] (2). Density functional theory calculations suggest a low-spin d, S = 1/2, electronic configuration of the central cobalt ion in 2 and, thus, are in line with the formulation of complex 2 as a genuine, low-spin Co(lV) nitride species. Although the reactivity of this species precludes handling above 50 K or isolation in the solid state, the N-migratory insertion product [(NH-BIMPN)Co](BPh) (3) is isolable and was reproducibly synthesized as well as fully characterized, including CHN elemental analysis, paramagnetic H NMR, IR, UV-vis, and EPR spectroscopy as well as SQUID magnetization and single-crystal X-ray crystallography studies. A computational analysis of the reaction pathway 2 → 3 indicates that the reaction readily occurs via N-migratory insertion into the Co-C bond (activation barrier of 2.2 kcal mol). In addition to the unusual reactivity of the nitride 2, the resulting divalent cobalt complex 3 is a rare example of a trigonal pyramidal complex with four different donor ligands of a tetradentate chelate—an N-heterocyclic carbene, a phenolate, an imine, and an amine—binding to a high-spin Co (II) ion. This renders complex 3 chiral-at-metal.
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