Organocopper Compounds: From Elusive to Isolable Species, from Early Supramolecular Chemistry with RCuI Building Blocks to Mononuclear R2–nCuII and R3–mCuIII Compounds. A Personal View

The first reports on copper-mediated organic reactions and speculations about the role of presumed organocopper compounds as intermediates or transient species date back to the early 20th century. Since that time, copper salt mediated and much later, copper-catalyzed C–X bond forming reactions (X = C, O, N) have been developed. Phenyl- and methylcopper(I) (highly explosive as a dry solid) were the first organocopper materials synthesized by Reich (1923) and Gilman (1952), respectively. However, it was not until the late 1960s and early 1970s that the first pure organocopper(I) compounds, which are also stable at room temperature, were isolated and structurally characterized. Recently, by the application of clever design and new synthetic approaches even organocopper(II) and -(III) compounds have been isolated, species that during the greater part of the last century were considered elusive. Significantly, these species had for some time been surmised, via kinetic and computational studies, to play a key role in copper-mediated and -catalyzed C–X bond forming reactions. In this personal account the various stages along which organocopper chemistry developed, with a steady pace, will be highlighted.