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Redox-Initiated Reactivity of Dinuclear β‑Diketiminatoniobium Imido Complexes

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journal contribution
posted on 2017-01-18, 18:23 authored by Benjamin M. Kriegel, Lara C. E. Naested, Grégory Nocton, K. V. Lakshmi, Trevor D. Lohrey, Robert G. Bergman, John Arnold
High-valent dichloride and dimethylniobium complexes 1 and 2 bearing tert-butylimido and N,N′-bis­(2,4,6-trimethylphenyl)-β-diketiminate (BDIAr) 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 NbIII–NbIV 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 NbV–NbV dimer 5 that formed from the reductive C–N bond cleavage of one of the BDIAr supporting ligands.