Uranium−Nitrogen Multiple Bonding: Isostructural Anionic, Neutral, and Cationic Uranium Nitride Complexes Featuring a Linear U═N═U Core

Reaction of the uranium (III) tris (anilide) complex (THF) U (Nt-BuAr) (3) (1, THF = tetrahydrofuran; Ar = 3, 5-Me (2) C (6) H (3) ) with MN (3) (M = Na, N (n-Bu) (4) ) results in the formation of the bimetallic diuranium (IV/IV) complexes M (mu-N) (U (N[t-BuAr) (3) ) (2) ] (M3), which feature a single nitride ligand engaged as a linear, symmetric bridge between two uranium centers. The stability of the U=N=U core across multiple charge states is illustrated by stepwise chemical oxidation of Na3 to the diuranium (IV/V) complex (mu-N) (U (Nt-BuAr) (3) ) (2) (3) and the diuranium (V/V) complex (mu-N) (U (N[t-BuAr) (3) ) (2) ]B (Ar (F) ) (4) 3B (Ar (F) ) (4) ; Ar (F) = 3, 5- (CF (3) ) (2) C (6) H (3). M3, 3, and 3B (Ar (F) ) (4) were characterized by NMR spectroscopy, single-crystal X-ray diffraction, and elemental analysis. The cyclic voltammogram of 3 reveals two clean, reversible one-electron electrochemical events at E (1/2) = -1. 69 and -0. 67 V, assigned to the 3 (-) /3 and 3/3 (+) redox couples, respectively. The X-ray crystal structures of N (n-Bu) (4) 3, 3, and 3B (Ar (F) ) (4) reveal a linear U=N=U core that contracts by only approximately 0. 03 A across the 3 (n) (n = -1, 0, +1) series, an effect that is rationalized as being primarily electrostatic in origin. 3B (Ar (F) ) (4) reacts with NaCN, eliminating NaB (Ar (F) ) (4) and forming the known diuranium (IV/IV) cyanoimide complex (mu-NCN) (U (Nt-BuAr) (3) ) (2), suggesting that the U=N=U core has metallonitrene-like character.