Tantalum Complexes of Diphenyldipyrrolide Dianion: Partial Hydrogenation of a Phenyl Ring

The reactivity of the pentavalent dipyrrolide complex {[Ph2C(C4H3N)2]2TaCl2}{Li(THF)4}·2THF was investigated. While an isostructral dimethyl derivative was readily prepared by
treatment with MeLi, reaction with NaHBEt3 gave a major reorganization, affording a
mixture of [Ph2C(C4H3N)2]Ta[(1,4-η1:η1-2,3-η2-C6H7PhC(C4H3N)2][Na(OEt2)] and [Ph2C(C4H3N)2]3Ta[Na(OEt2)]2·(OEt2). The first complex arises from partial hydrogenation of one
of the ligand phenyl rings performed by an intermediate Ta hydride. In the second case,
ligand scrambling occurred along with reduction of the metal center.