Jeffrey H. Wengrovius

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, 12 DMPE, 12 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.

X-ray crystallographic studies on octahedral oxo alkylidene complexes of tungsten(VI): W(O)(CHCMe3)(PMe3)2Cl2 and W(O)(CHCMe3)(PEt3)2Cl2

Abstract The reaction of Ta(CHCMe3)(PR3)2Cl3 and W(O)(OCMe3)4 yields mixed oxo-alkylidene complexes of tungsten(VI). Two have been subjected to single- crystal X-ray structural analysis. W(O)(CHCMe3)(PEt3)2Cl2 is disordered, but a full characterization of W(O)(CHCMe3)(PMe3)2Cl2 has been com- pleted. The oxo and alkylidene ligands occupy mutually cis locations with WO 1.701(15)A, WCHCMe3 2.006(15)A and