Reactivity of Organometallic Tantalum Complexes Containing a Bis(phenoxy)amide (ONO)3– Ligand with Aryl Azides and 1,2-Diphenylhydrazine

The reactivity of tantalum dimethyl and diphenyl complexes (ONOcat)TaMe2 (2) and (ONOcat)TaPh2 (3) with aryl azides and 1,2-diphenylhydrazine is reported. p-Tolyl azide inserts into a Ta–C bond of 2 or 3 to afford (ONOcat)TaMe(η2-MeNNN-p-C6H4Me) (6) or (ONOcat)TaPh(η2-PhNNN-p-C6H4Me) (7), respectively. In the presence of another 1 equiv of azide, another insertion occurs, affording the bis(triazenido) complexes (ONOcat)Ta(η2-MeNNN-p-C6H4Me)2 (4) and (ONOcat)Ta(η2-PhNNN-p-C6H4Me)2 (5). Complexes 2 and 3 also react with 1,2-diphenylhydrazine, resulting in the loss of 2 equiv of methane or benzene, respectively, along with 1/2 equiv of azobenzene. The tantalum-containing product was isolated as the pyridine adduct {(ONOcat)Ta(μ2-NPh)(py)}2 (8), which implicates a tantalum(III) intermediate. The viability of this (ONOcat)TaIII intermediate was proven by KC8 reduction of (ONOcat)TaCl2 (1) in THF, resulting in activation of a C–O bond of THF and formation of {(ONOcat)Ta(μ-O(CH2)3CH2)}2 (10), which was characterized by single-crystal X-ray diffraction studies.