Attempts to prepare alkylidene zirconium complexes by α-hydrogen atom abstraction

We prepared several new neopentyl halide complexes of zirconium in order to test whether they could be induced to lose neopentane and give neopentylidene complexes by adding phosphorus or nitrogen donor ligands. ZrNp₂X₂ (X  Cl or Br) can be prepared in ether and isolated as a dietherate (an oil). It reacts with L (L  PMe₃, PMe₂Ph, NEt₃, $\text{1}\text{2}$ DMPE, $\text{1}\text{2}$ TMEDA) to give ZrNp₂X₂L₂. ZrNp₃Cl can be prepared by adding MgNp₂ to ZrNp₂Cl₂(ether)₂ and isolated by sublimation in 25% yield. On adding PMe₃ or TMEDA, it disproportionates to ZrNp₄ and ZrNp₂Cl₂L₂. ZrCp″NpCl₂ (Cp″ = η⁵-C₅Me₅), ZrCp″Np₂Cl, and ZrCp″Np₃ were prepared by adding MgNp₂ to ZrCp″Cl₃. Only the last is a solid, only the first forms an adduct, ZrCp″NpCl₂(PMe₃). None of the complexes decomposed to tractable products in the presence of L. Photolysis of ZrNp₂Cl₂(PMe₃)₂ yielded Zr(PMe₃)₂Cl₃]₂ by an apparently complex reaction initiated by homolytic ZrNp bond fission.