Nitrene and Carbene Chemistry at Middle and Late First-Row Metals in Bis(alkoxide) Ligand Environments

Our research focuses on the design of reactive metal centers for N-N, C-N, and C-C bond formation. Toward this goal, we developed a series of new middle and late first-row transition metal complexes in bis(alkoxide) ligand environment and are currently exploring their reactivity in nitrene and carbene transfer. We have recently reported synthesis of “quasi-two-coordinate” complexes M(OR)2(THF)2 (OR = OC(tBu)2Ph, M = Mn, Fe, Co) that proceeds via cluster intermediates featuring rare seesaw geometry. The iron(II) complex Fe(OR)2(THF)2 undergoes facile reaction with aliphatic and aromatic azides. The reaction with aliphatic azides results in the reductive coupling of azides to form the iron(III) hexazene complex (RO)2Fe(μ-κ2:κ2-RN6R)Fe(OR)2. In contrast, the reaction of Fe(OR)2(THF)2 with aromatic azides (ArN3) leads to the formation of azoarenes ArNNAr, with concomitant liberation of dinitrogen. The reaction is catalytic for bulky azides, and is postulated to proceed via metal-nitrene intermediate [Fe(OR)2(NAr)]. Mechanistic, spectroscopic, structural, and theoretical studies will be presented. For chromium, stable Cr(OR)2(NAr) complexes are obtained, which display catalytic reactivity in nitrene transfer to isocyanides. We will also describe our most recent results concerning synthesis, characterization, and reactivity of the formally Co(IV)-carbene complex.
Stanislav Groysman, Wayne State University
Nitrene and Carbene Chemistry at Middle and Late First-Row Metals in Bis(alkoxide) Ligand Environments