Design of Ligands Which Improve Cu(I) Catalysis

It seemed plausible that tri- and tetraamine ligands with a substituent which binds to Cu(I) but not to Cu(II), e.g., an allyl, stabilize Cu(I) in aqueous solutions and shift its redox potential cathodically relative to Cu + (aq). Therefore, the ligands N(CH 2 CH 2 NR 2 ) 2 (CH 2 CH 2 NRCH 2 CH CH 2 ) (R = H or CH 3 ) were synthesized. These ligands indeed stabilize Cu(I) in aqueous solutions and shift the redox potential of the Cu(II)/Cu(I) and Cu(I)/Cu(0) couples cathodically relative to Cu 2+/+ (aq) and the complexes Cu II L/Cu I L where L = R 2 NCH 2 CH 2 NRCH 2 CH 2 NR(CH 2 CH CH 2 ). Therefore, the copper complexes with the new ligands are expected to be better catalysts to processes in which the redox step is the rate-determining step.