N-Heterocyclic “Pincer” Dicarbene Complexes of Cobalt(I), Cobalt(II), and Cobalt(III)

The complex Co(C-N-C)Br-2 (C-N-C = 2,6-bis(aryl-imidazol-2-ylidene)pyridine, aryl = 2,6-(Pr2C6H3)-C-i), prepared by aminolysis of Co[N(SiMe3)(2)](2) with the corresponding imidazolium salt, (CH-N-CH)Br-2, was methylated to the square-planar Co(C-N-C-)(CH3) and oxidized with BrN(SiMe3)(2) to give Co(C-N-C)Br-3. The new Co(II), Co(III), and Co(I) complexes show no ethylene polymerization activity.