Nickel(II) Cyclen Complexes Bearing Ancillary Amide Appendages for the Electrocatalytic Reduction of CO2

Substituted cyclen complexes of nickel(II) containing either one or two pendant amide groups were prepared as potential electrocatalysts for the reduction of CO2 to CO. Four complexes bearing two amide substituents with either tert-butyl ([Ni(DMCy2tBu)](PF6)2), mesityl ([Ni(DMCy2mes)](PF6)2), 3,5-bis(trifluoromethyl)phenyl ([Ni(DMCy2CF3)](PF6)2) and pentafluorophenyl ([Ni(DMCy2C6F5)](PF6)) groups, were all easily prepared and isolated without the need for column chromatography. Similarly, two other nickel(II) cyclen derivatives containing a single mesityl substituted amide pendant ([Ni(DMCyMes)(Cl)](PF6) and [Ni(TrMCyMes)(Cl)]Cl) were also prepared. X-ray crystal structures were obtained for each of complexes and show that the pendant amides are bound to the nickel(II) center at the core of the cyclen complexes. The amides coordinate to the central metal via either the amide oxygen or nitrogen atoms depending on the electronic properties of the amide group. The ability of each of the six complexes to elec...