A Three-Coordinate Cobalt(-I) Dinitrogen Complex

While most reported Co(-I) complexes are coordinatively saturated, we report herein a 16e– Co(-I) complex [(cyIDep)Co(η2-vtms)(N2)Na(OEt2)]2 (where cyIDep = 1,3-di(2′,6′-diethylphenyl)-4,5-(CH2)4-imidazol-2-ylidene; and vtms = vinyltrimethylsilane). The Co(-I) complex is isolated from the reaction of [(cyIDep)Co(η2-vtms)2] with sodium under a dinitrogen atmosphere. It features short Co–N (1.695(3)/1.695(3) Å) and long N–N bonds (1.166(4)/1.168(3) Å). Theoretical study indicates the presence of 2-fold Co-to-N2 π-backdonation interactions in the three-coordinate Co(-I) species, which might lead to thermodynamic gains to the unusual alkene-to-N2 ligand exchange reaction that gives the Co(-I) complex. The attempts to functionalize the dinitrogen ligand in the Co(-I) complex with Me3SiCl and a N-heterocyclic silylene lead to the isolation of the cobalt(I) alkyl complex [(cyIDep)Co(C(SiMe3)2Me)] and the cobalt(0) complex [(t-BuNHSi)(cyIDep)Co(η2-vtms)] (t-BuNHSi = 1,3-bis(tert-butyl)-1,3-diaza-2-silacyclopent-4-en-2-ylidene), respectively, rather than the desired products.