The “couple” was popularized after the report by Simmons and Smith, published in 1959, on its application as an activated source of zinc required for formation of an organozinc reagent in the Simmons–Smith cyclopropanation of alkenes.
The couple is frequently prepared as a darkly-colored powder and is slurried in an ethereal solvent prior to being used in slight excess relative to the substrate.
Activation of zinc by copper is essential to the couple’s utility, but the origin of this effect is poorly documented.
An early method for the synthesis of zinc–copper couple entailed treatment of a mixture of zinc dust and copper(II) oxide with hydrogen gas at 500 °C.
[1] A more convenient and cheaper method proceeds by treatment of zinc powder with hydrochloric acid and copper(II) sulfate.