Organozinc Pivalate Reagents: Segregation, Solubility, Stabilization, and Structural Insights

The pivalates RZnOPiv⋅Mg(OPiv)X⋅ n  LiCl (OPiv=pivalate; R=aryl; X=Cl, Br, I) stand out amongst salt‐supported organometallic reagents, because apart from their effectiveness in Negishi cross‐coupling reactions, they show more resistance to attack by moist air than conventional organometallic compounds. Herein a combination of synthesis, coupling applications, X‐ray crystallographic studies, NMR (including DOSY) studies, and ESI mass spectrometric studies provide details of these pivalate reagents in their own right. A p ‐tolyl case system shows that in [D 8 ]THF solution these reagents exist as separated Me( p ‐C 6 H 4 )ZnCl and Mg(OPiv) 2 species. Air exposure tests and X‐ray crystallographic studies indicate that Mg(OPiv) 2 enhances the air stability of aryl zinc species by sequestering H 2 O contaminants. Coupling reactions of Me( p ‐C 6 H 4 )ZnX (where X=different salts) with 4‐bromoanisole highlight the importance of the presence of Mg(OPiv) 2 . Insight into the role of LiCl in these multicomponent mixtures is provided by the molecular structure of [(THF) 2 Li 2 (Cl) 2 (OPiv) 2 Zn].