Mechanisms of Activating Agents to Form Organozinc Reagents from Zinc Metal: Lessons for Reaction Design.

Activating agents enable the efficient preparation of organozinc complexes from zinc metal and organohalides, but their mechanisms had been obscured by the heterogeneous nature of these systems. Fluorescence microscopy, with the sensitivity to detect surface reaction intermediates, reveals distinct activating mechanisms of widely used activation strategies: trimethylsilyl chloride, LiCl, DMSO, and Rieke zinc powder. The resulting development of mechanistic models provides a better understanding of the oxidative-addition-solubilization sequence in organozinc reagent formation and contains lessons for methods development.