Grignard reagents, bonding metal catalyzed addition

Zirconocene dichlondc and related complexes catalyze the addition of trialkylaluminum compounds to tenninal acetylenes7 and olefins8 as well as the addition of ethyl, propyl, and butyl Grignard reagents to alkenes.9-12 These transformations occur with a high degree of regiosclectivity (cf. hydroboration), such that the metal atom always adds to the end position of a terminal multiple bond like that in 25. If addition is to a triple bond, M and R in the product are cis to each other... 

Although chlorosilanes are the most readily available silylating reagents, their use in catalytic silylation has not yet been achieved, probably because of the difficulty of oxidative addition of the Si-Cl bonds to transition metal centers. The first example of the transition metal-catalyzed silylation of alkenes with chlorosilanes and silylsulfides, silylselenides, and silyltellurides has been reported [33]. This reaction proceeds under mild conditions with a catalytic amount of a zirconocene complex in the presence of a Grignard reagent to give alkenylsilanes and/or allyl-silanes. 

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