Synthesis and Reactions of Tungsten Oxo Vinylalkylidene Complexes: Reactions of WCl2(O)(PX3) (X = OMe, R) Precursors with 3,3-Diphenylcyclopropene

Complexes of the type WCl 2 (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 η 2 -cyclopropene complexes. Spectroscopic data of W(η 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 cis to the apical oxo ligand. The thermal rearrangement of the η 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(CH 3 )(CF 3 ) 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.