Towards Heteroleptic Dicoordinate Cu(II) Complexes.

In this work we detail our efforts to systematically generate stable dicoordinate Cu(II) 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 RCuOSO 3 Et ( 2 ), [RCu(THF)][Cu(NTf 2 ) 2 ] ( 3 ) and RCuNTf 2 ( 4 ) could be isolated. Spectroscopic indications corroborate more Cu(I) than Cu(II) character in all RCuX derivatives.