[Me2NN]Co(η6-toluene): OO, NN, and ON Bond Cleavage Provides β-Diketiminato Cobalt μ-Oxo and Imido Complexes

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Abstract
The synthesis and structure of a novel β-diketiminato Co(I) arene adduct [Me2NN]Co(η6-toluene) (2) are described, that serves as a synthon to the reactive, “naked” 12-electron [Me2NN]Co fragment via loss of toluene in its reactions with dioxygen, organoazides, and a nitrosobenzene. Exposure of 2 to dioxygen in ether leads to {[Me2NN]Co}2(μ-O)2 (3), a rare example of a cobalt−oxo complex thermally stable at room temperature. The X-ray structure of 3 reveals a short Co−Co separation of 2.716(4) Å and exhibits positional disorder for the bridging oxo groups; the predominant configuration contains oxygen atoms in square-planar sites with short Co−O distances (1.784(3) and 1.793(4) Å). Reaction of 2 with organoazides N3R (R = 3,5-Me2C6H3 (Ar) or 1-adamantyl (Ad)) results in the formation of imido complexes whose structure depends on the nature of the azido substituent. The synthesis and structures of both {Me2NN]Co}2(μ-NAr)2 (4) with arylimido groups in tetrahedral bridging sites or the three-coordinate, 16-electron [Me2NN]Co⋮NAd (5) are described. The X-ray structure of terminal imide 5 reveals a short Co−N bond distance (1.624(4) Å) and only somewhat bent imido linkage (Co−N−C = 161.5(3)°) consistent with a significant degree of multiple bond character. Complex 2 cleaves the ON bond of the nitrosobenzene ONAr (Ar = 3,5-Me2C6H3) to form the binuclear oxo−imido complex {[Me2NN]Co}2(μ-O)(μ-NAr) (6) that possesses a structure intermediate between square-planar 3 and tetrahedral 4 in which the [Me2NN]Co fragments are mutually orthogonal.

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