Reactivity of [K3(phen)8][Cu(NPh2)2]3—a possible intermediate in the copper(i)-catalyzed N-arylation of N-phenylaniline

Abstract

Complex [K₃(phen)₈][Cu(NPh₂)₂]₃ (1, phen = phenanthroline) was isolated from the catalytic C–N cross coupling reaction based on the CuI-phen-tBuOK catalytic system. Complex 1 can react with 4-iodotoluene to give 4-methyl-N,N-diphenylaniline (3a) in 50% yield (based on all available NPh₂⁻ ligands of complex 1). In addition, 1 can also work as an effective catalyst for the C–N coupling reactions under the same reaction conditions, indicating that 1 may be an effective intermediate of the catalytic system. In the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), a radical scavenger, the stoichiometric reaction between complex 1 and 4-iodotoluene was significantly quenched to give a low yield of 12%. The results suggest that the radical path dominates in the reaction, with (phen)KNPh₂ as the possible radical source. The structures of 1 and (phen)KNPh₂ were both determined by single crystal X-ray diffraction studies.