Access to Heterobimetallic MII/CuI Complexes with a Multichelate Platform and Their Reactivity Studies in CO2RR

We describe the selective formation of heterobimetallic complexes, exploiting the coordination trends of the developed bis-terpyridyl trans -1,2-cyclohexadiamine platform ( L ). Following a stepwise addition, we first reacted ligand L toward tetrakisacetonitrile transition metal precursors, [M(MeCN) 4 ][BF 4 ] 2 (where M = Fe or Ni), to generate the monometallic complexes 1 ([FeL][BF 4 ] 2 ) and 2 ([NiL][BF 4 ] 2 ). These species were later combined with the tetrakisacetonitrile precursor [Cu(MeCN) 4 ][BF 4 ], generating the corresponding heterobimetallic complexes 3 ([FeCuL(MeCN) 2 ][BF 4 ] 3 ) and 4 ([NiCuL(MeCN) 2 ][BF 4 ] 3 ). The four species obtained, in high yields, have been structurally characterized. Their cyclic voltammetry analysis revealed the impact of the Cu I -atom presence on the heterobimetallic complexes under argon and carbon dioxide (CO 2 ) atmospheres. Controlled potential electrolysis studies revealed the instability of complexes 1 – 4 toward CO2RR, generating the heterogeneous material in solution and on the electrode surface. In contrast, CO 2 photoreduction studies revealed higher stability and photocatalytic activity for the Fe II -based complexes ( 1 and 3 ), generating CO with 88% selectivity.