Hydrotris(triazolyl)borate complexes as functional models for Cu nitrite reductase: the electronic influence of distal nitrogens.

Hydrotris(triazolyl)borate (Ttz) ligands form CuNO(x) (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](+)[(Ttz(tBu,Me))Cu(I)NO(2)](-) has been synthesized and characterized and allows for the stoichiometric reduction of NO(2)(-) 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.