Synthesis and investigations of the crystal structure of a dinuclear diazadiene molybdenum oxo-imido complex with a unique N3Mo(mu-O)(2)MoN3 core

摘要

Ligand metathesis of the diimido and dioxo precursor complexes [Mo(X)(2)Cl-2(DME)] (X = O, NtBu) leads to the mixed oxo-imido derivative [Mo(NtBu)(O)Cl-2(DME)] (1). By treatment with Li(2)DAD (DAD = 1,4-di-tert-butyl-1,4-diazabuta-1,3-diene), 1 is converted into the complex [Mo(NtBu)(O)(DAD)](2) (2). The crystal structure determination on a nonmerohedral twin of 2 reveals a dinuclear molecular structure with nearly symmetrical bridging oxygen atoms. The smaller oxo ligand tends to be a better bridging functionality than the imido ligand; the unprecedented N3Mo(mu-O)(2)MoN3 configuration is favored over a ON2Mo(mu-N)(2)MoN2O core. Compared to other known molybdenum DAD complexes, 2 reveals some degree of pyramidalization at the nitrogen atoms of the DAD ligand. In accord with the Mo-N, N-C, and C-C bond lengths, complex 2 is best described as an ene-diamido complex of formally six-valent molybdenum.