Copper(I) Complexes with Trispyrazolylmethane Ligands: Synthesis, Characterization, and Catalytic Activity in Cross-Coupling Reactions

Three novel Cu­(I) complexes bearing tris­(pyrazolyl)­methane ligands, Tpmx, have been prepared from reactions of equimolar amounts of CuI and the ligands Tpm, (HC­(pz)3), Tpm*, (HC­(3,5-Me2-pz)3), and TpmMs, (HC­(3-Ms-pz)3). X-ray diffraction studies have shown that the Tpm and TpmMs derivatives exhibit a 2:1 Cu:ligand ratio, whereas the Tpm* complex is a mononuclear species in nature. The latter has been employed as a precatalyst in the arylation of amides and aromatic thiols with good activity. The synthesis of a Tpm*Cu­(I)-phthalimidate, a feasible intermediate in this catalytic process, has also been performed. Low temperature 1H NMR studies in CDCl3 have indicated that this complex exists in solution as a mixture of two, neutral and ionic forms. Conductivity measurements have reinforced this proposal, the ionic form predominating in a very polar solvent such as DMSO. The reaction of Tpm*Cu­(I)-phthalimidate with iodobenzene afforded the expected C–N coupling product in 76% yield accounting for its role as an intermediate in this transformation.