Synthesis of High Oxidation State Molybdenum Imido Heteroatom-Substituted Alkylidene Complexes

Abstract

Reactions between Mo(NAr)(CHR)(Me[subscript 2]Pyr)(OTPP) (Ar = 2,6-i-Pr[subscript 2]C[subscript 6]H[subscript 3], R = H or CHCMe[subscript 2]Ph, Me[subscript 2]Pyr = 2,5-dimethylpyrrolide, OTPP = O-2,3,5,6-Ph[subscript 4]C[subscript 6]H) and CH[subscript 2]═CHX where X = B(pin), SiMe[subscript 3], N-carbazolyl, N-pyrrolidinonyl, PPh[subscript 2], OPr, or SPh lead to Mo(NAr)(CHX)(Me[subscript 2]Pyr)(OTPP) complexes in good yield. All have been characterized through X-ray studies (as an acetonitrile adduct in the case of X = PPh[subscript 2]). The efficiencies of metathesis reactions initiated by Mo(NAr)(CHX)(Me[subscript 2]Pyr)(OTPP) complexes can be rationalized on the basis of steric factors; electronic differences imposed as a consequence of X being bound to the alkylidene carbon do not seem to play a major role. Side reactions that promote catalyst decomposition do not appear to be a serious limitation for Mo═CHX species.