Reactions between Mo(NAr)(CHR)(Me<sub>2</sub>Pyr)(OTPP)
(Ar = 2,6-<i>i</i>-Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>, R = H or CHCMe<sub>2</sub>Ph, Me<sub>2</sub>Pyr = 2,5-dimethylpyrrolide,
OTPP = O-2,3,5,6-Ph<sub>4</sub>C<sub>6</sub>H) and CH<sub>2</sub>CHX
where X = B(pin), SiMe<sub>3</sub>, <i>N</i>-carbazolyl, <i>N</i>-pyrrolidinonyl, PPh<sub>2</sub>, OPr, or SPh lead to Mo(NAr)(CHX)(Me<sub>2</sub>Pyr)(OTPP) complexes in good yield. All have been characterized
through X-ray studies (as
an acetonitrile adduct in the case of X = PPh<sub>2</sub>). The efficiencies
of metathesis reactions initiated by Mo(NAr)(CHX)(Me<sub>2</sub>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 MoCHX species