Hydrotris(triazolyl)borate Complexes as Functional Models for Cu Nitrite Reductase: The Electronic Influence of Distal Nitrogens

Hydrotris­(triazolyl)­borate (Ttz) ligands form CuNOx (x = 2, 3) complexes for structural and functional models of copper nitrite reductase. These complexes have distinct properties relative to complexes of hydrotris­(pyrazolyl)­borate (Tp) and neutral tridentate N-donor ligands. The electron paramagnetic resonance spectra of five-coordinate copper complexes show rare nitrogen superhyperfine couplings with the Ttz ligand, indicating strong σ donation. The copper­(I) nitrite complex [PPN]+[(TtztBu,Me)­CuINO2]− has been synthesized and characterized and allows for the stoichiometric reduction of NO2– to NO with H+ addition. Anionic Cu­(I) nitrite complexes are unusual and are stabilized here for the first time because Ttz is a good π acceptor.