Synthesis and reactions of tungsten oxo vinylalkylidene complexes: Reactions of WCl2(O)(PX(3)) (X=OMe, R) precursors with 3,3-diphenylcyclopropene

Complexes of the type WCl2(O)[PX(3)](3) (PX(3) = P(OMe)(3) (1); PMePh(2) (2)) were synthesized according to procedures previously described in the literature. Upon treatment with 3,3-diphenylcyclopropene, complexes 1 and 2 afforded the corresponding eta(2)-cyclopropene complexes. Spectroscopic data of W(eta(2)-diphenylcyclopropene)Cl-2(O)[PX(3)](2) (PX(3) = P(OMe)(3) (4); PMePh(2) (5)) were consistent with an octahedral geometry in which the two mutually trans PX(3) ligands and the cyclopropene ligand occupy equatorial positions cia to the apical oxo ligand. The;thermal rearrangement of the eta(2)-cyclopropene complexes leads to the dimerization product of 3,3-diphenylcyclopropene: 1,1,6,6-tetraphenyl-1,3,5-hexatriene. The presence of carbene species before the dimerization occurs has been demonstrated. Upon treatment with 2 equiv of lithium hexafluoro-tert-butoxide, complexes 4 and 5 give the vinyl alkylidene complexes W(=CHCH=CPh(2))(O)[OC(CH3)(CF3)(2)](2)[PX(3)] (PX(3) = P(OMe)(3) (10); PMePh(2)(7)). The spectroscopic data of 10 and 7 indicated a distorted trigonal bipyramid, where the oxo and alkylidene ligands are cis to each other and placed in the equatorial plane.