organozincs

Organozincs are organometallic compounds containing carbon–zinc bonds. They exist as organozinc halides of the form RZnX (X = Cl, Br, I) and as dialkylzincs of the form R2Zn, among other derivatives. In organic synthesis they are used as relatively mild nucleophiles and as cross-coupling partners, offering greater tolerance for sensitive functional groups than many Grignard or organolithium reagents.

Preparation methods include transmetalation from organomagnesium reagents with zinc salts (for example, R-MgX + ZnCl2 → RZnX + MgCl2) and direct insertion of zinc metal into organic halides under activating conditions, often with copper or nickel co-catalysts and additives such as LiCl. Dialkylzincs can be generated by transmetalation from other zinc species or through zincation of organohalides under suitable conditions.

In reactivity, organozincs are valued for their compatibility with a range of functional groups and their ability to participate in carbon–carbon bond formation under milder conditions than many other organometallic reagents. A key application is the Negishi cross-coupling, where RZnX couples with aryl or vinyl halides under palladium or nickel catalysis to form new C–C bonds. They also participate in various carbonyl additions and other coupling processes, providing versatile routes to complex molecules.

Handling and limitations: organozincs are typically air- and moisture-sensitive and are often prepared and used in situ. Some dialkylzinc compounds are highly reactive and pyrophoric, requiring careful inert-atmosphere techniques. The practical scope depends on the reagent, the substrate, and the catalyst system, with cost and accessibility of zinc reagents also considered in planning syntheses.