Redox-Initiated Reactivity of Dinuclear β‑Diketiminatoniobium Imido Complexes

High-valent dichloride and dimethylniobium complexes 1 and 2 bearing tert-butylimido and N,N′-bis­(2,4,6-trimethylphenyl)-β-diketiminate (BDI^Ar) ligands were prepared. The dimethyl complex reacted with dihydrogen to release methane and generate the hydride-bridged diniobium­(IV) complex 3 in high yield. One-electron oxidation of 3 with silver salts resulted in the release of dihydrogen and conversion to a mixed-valent Nb^III–Nb^IV complex, 4, that displayed a frozen-solution X-band electron paramagnetic resonance signal consistent with a slight dissymmetry between the two Nb centers. Spectroscopic and computational analysis supported the presence of Nb–Nb σ-bonding interactions in both 3 and 4. Finally, one-electron reduction of 4 resulted in conversion to the highly dissymmetric Nb^V–Nb^V dimer 5 that formed from the reductive C–N bond cleavage of one of the BDI^Ar supporting ligands.