Hydroalumination of a Dinuclear Tantalum Dinitrogen Complex: N−N Bond Cleavage and Ancillary Ligand Rearrangement

Abstract

The addition of diisobutylaluminum hydride (DIBAL) to the side-on end-on dinitrogen complex ([NPN]Ta)2(μ-η1:η2-N2)(μ-H)2, 1 (where [NPN] = (PhNSiMe2CH2)2PPh), is described. The two end products are diastereomeric rotational isomers in which N−N bond cleavage has occurred with an Al(iBu)H group attached to one of the nitride atoms. The reaction proceeds through addition of DIBAL to 1 to generate a thermally sensitive intermediate that has been characterized in solution as the result of Al−H addition across the TaN2 moiety, namely, ([NPN]TaH)(μ-η1:η2-NNAliBu2)(μ-H)2(Ta[NPN), 2. This material subsequently rearranges via a second thermally labile intermediate to ultimately generate two diastereomeric end products that show N−N bond cleavage, loss of H2, loss of an aluminum isobutyl group, and NPN ligand migration from tantalum to aluminum. Both of these complexes have been isolated in crystalline form and analyzed by single-crystal X-ray diffraction. The second thermally sensitive intermediate has been charac...