Dinitrogen Binding and Silylation by Bis(ketimino)carbazolide Complexes of Iron and Cobalt

We report the coordination chemistry of a bulky 1,8-bis(ketimino)carbazole (HL) ligand and the reactivity of the corresponding iron(II) and cobalt(II) chloride complexes [LFeCl] (1) and [LCoCl] (2). Upon one-electron reduction of 1 and 2 under a dinitrogen atmosphere, N2 binds to the reduced metal centers to generate the corresponding square planar Fe(I) and Co(I) complexes [LFe(N2)] (3) and [LCo(N2)] (4·N2), respectively. While further reduction of 3 generates the formally Fe(0) species [LFe(N2)]−, the reduction of 4·N2 affords a three-coordinate [LCo(0)] complex (7) with the loss of N2 from the metal center. Density functional theory (DFT) calculations suggest noninnocent behavior of the ligand. Both 3 and 4 can catalyze the silylation of N2 using the combination of KC8 and Me3SiCl reagents to produce N(SiMe3)3, where low temperature and batch addition significantly improve the yields to up to 52%.