Structure and nitrite reduction reactivity study of bio-inspired copper(i)-nitro complexes in steric and electronic considerations of tridentate nitrogen ligands.

Two copper(i)-nitro complexes [Tpm3-tBuCu(NO2)] (1) and [(Ph3P)2N][Tp3-tBuCu(NO2)] (2), containing steric bulky neutral tris(3-tert-butylpyrazolyl)methane and anionic hydrotris(3-tert-butylpyrazolyl)borate ligands, have been synthesized and characterized. Complex 2 adopts a unique κ2-binding mode of Tp3-tBu around the copper(i)-nitro environment in the solid state and shows a four-coordinated tetrahedral geometry surrounded by a nitro and three pz3-tBu groups in solution. Both complexes 1 and 2 allow for the stoichiometric reduction of NO2- to NO with H+ addition. The results of this effort show that increasing steric bulk and electron donation properties on the nitrogen ancillary ligand will improve the nitrite reduction ability of the copper(i)-nitro model complexes.