Nucleophilicity at copper(-I) in a compound with a Cu–Mg bond

Abstract A vast number of chemical reactions rely on the near-inevitable preference of copper for positive oxidation states to make useful compounds. In this work, we report that the reaction of an N-heterocyclic carbene (NHC) ligated copper alkoxide with a dimeric magnesium(I) compound results in a stable compound with a copper-magnesium bond, which conforms to the formal oxidation state of Cu(-I). Single crystal X-ray crystallography and quantum chemical calculations further support the assignment of a sub-zero oxidation state at copper. The Cu-Mg bond acts as a source of the cupride anion, transferring the NHC-copper fragment to electrophilic s-, p-, and d-block atoms to make known and new copper-containing compounds.