[reaction: see structure] The first examples of efficient electrophilic Zr-catalyzed carbomagnesations are disclosed, where in contrast to previous catalytic carbomagnesations the alkyl moiety of the electrophile is transferred (vs that of the Grignard reagent). The identity of the Grignard reagent is manipulated so that Zr-Mg exchange is facilitated, leading to the formation of alkylmagnesium halide products.