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

Abstract

Two copper(I)–nitro complexes [Tpm^3-tBuCu(NO₂)] (1) and [(Ph₃P)₂N][Tp^3-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 Tp^3-tBu around the copper(I)–nitro environment in the solid state and shows a four-coordinated tetrahedral geometry surrounded by a nitro and three pz^3-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.