In operando fluorescence microscopy facilitated the direct observation of organozinc intermediate complexes on the surface of zinc particles, via oxidative addition of alkyl carbon–iodide sigma bonds into zinc. The reaction required 24 h at room temperature under N<sub>2</sub> to complete, and the organozinc intermediates were observed as bright green regions on the surface of the dark zinc particles. The analogous aryl carbon–iodide oxidative addition did not proceed at room temperature, but when the reaction was heated to 60 °C for 24 h under N<sub>2</sub>, bright green regions on the dark zinc particles were observed, consistent with organozinc intermediate formation. Lithium chloride was used to determine the mechanism of the direct insertion, which resulted in testing five mechanistic hypotheses. When lithium chloride was added to the solution after an initial observation window, the surface of the zinc particles immediately became dark, and subsequent analysis of new regions showed this effect was not due to photobleaching of the fluorescent core. The data are consistent with lithium chloride solubilizing organozinc reagents from the surface after oxidative addition. Trimethylsilyl chloride enables the removal of zinc oxide from the surface of zinc particles, resulting in increasingly pure zinc for direct insertion.

Role of LiCl in generating soluble organozinc reagents

253rd National Meeting (2017)

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