Synthesis of Tungsten Oxo Alkylidene Complexes

Abstract

Reaction of W(O)[subscript 2](CH[subscript 2]-t-Bu)[subscript 2](bipy) with a mixture of ZnCl[subscript 2](dioxane), PMe[subscript 2]Ph, and trimethylsilyl chloride in toluene at 100 °C produced the known tungsten oxo alkylidene complex W(O)(CH-t-Bu)Cl[subscript 2](PMe[subscript 2]Ph)[subscript 2] (1a) in 45% isolated yield. The neophylidene analogue W(O)(CHCMe[subscript 2]Ph)Cl[subscript 2](PMe[subscript 2]Ph)[subscript 2] was prepared similarly in 39% yield. The reaction between 1a and LiOR (LiOR = LiOHIPT, LiOHMT) in benzene at 22 °C led to formation of the off-white W(O)(CH-t-Bu)Cl(OR)(PMe[subscript 2]Ph) complexes 4a (OR = OHMT = 2,6-dimesitylphenoxide) and 4b (OR = OHIPT = 2,6-(2,4,6-triisopropylphenyl)[subscript 2]phenoxide). Compound 4a serves as a starting material for the synthesis of W(O)(CH-t-Bu)(OHMT)(2,6-diphenylpyrrolide) (6), W(O)(CH-t-Bu)[N(C[subscript 6]F[subscript 5])[subscript 2]](OHMT)(PMe[subscript 2]Ph) (7), W(O)(CH-t-Bu)[OSi(t-Bu)[subscript 3]](OHMT) (8), and W(O)(CH-t-Bu)(OHMT)[subscript 2] (10). The reaction between 8 and ethylene was found to yield the square-pyramidal metallacyclobutane complex W(O)(C[subscript 3]H[subscript 6])[OSi(t-Bu)[subscript 3]](OHMT) (9), while the reaction between 10 and ethylene was found to yield the square-pyramidal metallacyclobutane complex W(O)(C[subscript 3]H[subscript 6])(OHMT)[subscript 2] (11). Compound 11 loses ethylene to yield isolable W(O)(CH[subscript 2])(OHMT)[subscript 2] (12). X-ray structures were determined for 6, 7, 9, and 12.