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(CH₂CH₂NR₂)₂(CH₂CH₂NRCH₂CH=CH₂) (R = H or CH₃) 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(O) couples cathodically relative to Cu(2+/+)(aq) and the complexes Cu(II)L/Cu(I)L where L = R₂NCH₂CH₂NRCH₂CH₂NR(CH₂CH₂=CH₂). 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.