Synthesis and Investigations of the Crystal Structure of aDinuclear Diazadiene Molybdenum Oxo‐Imido Complex with a Unique N 3 Mo(μ‐O) 2 MoN 3 Core

Ligand metathesis of the diimido and dioxo precursor complexes [Mo(X) 2 Cl 2 (DME)] (X = O, N t Bu) leads to the mixed oxo‐imido derivative [Mo(N t Bu)(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(N t Bu)(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 N 3 Mo(μ‐O) 2 MoN 3 configuration is favored over a ON 2 Mo(μ‐N) 2 MoN 2 O 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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)