Bis(methylidene) Complex of Tantalum Supported by a PNP Ligand

Reaction of (PNP)Li with TaF5 produces pentagonal-bipyramidal (PNP)TaF4 (2). Alkylation of 2 with MeMgBr allows for the isolation of (PNP)TaMe4 (3). (PNP)TaMe4 (3) evolves thermally and/or photochemically into a bis(methylidene) complex (PNP)Ta(CH2)2 (4). The identity of the latter has been established by X-ray structural, NMR spectroscopic, and DFT computational studies. It does not appear that 4 possesses agostic interactions in solution.