Towards Heteroleptic Dicoordinate Cu(II) Complexes

In this work we detail our efforts to systematically generate stable dicoordinate CuII complexes. Initial experiments via metathesis reactions of a bulky potassium carbazolide (RK) with copper(II) salts indeed yielded a stable product, RCuOTf (1). However, subsequent attempts to grasp systematic synthetic access to complexes of the type RCuX (X=monoanionic ligand) proved difficult as many of the complexes rapidly decomposed in solution. By using triflate-related ligands such as ethyl sulfate and bistriflimide, the additional dicoordinate copper complexes RCuOSO3Et (2), [RCu(THF)][Cu(NTf2)2] (3) and RCuNTf2 (4) could be isolated. Spectroscopic indications corroborate more CuI than CuII character in all RCuX derivatives.