Scorpionates bearing nitro substituents: mono-, bis- and tris-(3-nitro-pyrazol-1-yl)borate ligands and their copper(i) complexes

Abstract

Two scorpionates sodium trihydro(3-nitro-pyrazol-1-yl)borate (Na[H₃B(3-(NO₂)pz)]) and sodium hydrotris(3-nitro-pyrazol-1-yl)borate (Na[HB(3-(NO₂)pz)₃]), featuring electron withdrawing substituents, have been synthesized in high yield starting from 3(5)-nitropyrazole and sodium borohydride. The treatment of CuX (X = (CH₃CN)₄PF₆, Cl or I) with Na[H₃B(3-(NO₂)pz)], Na[HB(3-(NO₂)pz)₃] or the related bis(pyrazolyl)borate Na[H₂B(3-(NO₂)pz)₂] in the presence of triphenylphosphine or tert-butyl isocyanide afforded the corresponding (azolyl)borate supported copper(I) triphenylphosphine or tert-butyl isocyanide adducts. These compounds have been characterized by elemental analyses, FT-IR, ESI-MS and multinuclear NMR spectroscopy. X-Ray crystal structures of [H₃B(3-(NO₂)pz)]Cu[P(C₆H₅)₃]₂, [H₂B(3-(NO₂)pz)]Cu(CNt-Bu)₂, and [HB(3-(NO₂)pz)₃]Cu[P(C₆H₅)₃], as well as that of the {[HB(3-(NO₂)pz)₃]Na}₄ are also reported. The latter displays a particularly interesting tetrameric structure with each tris(pyrazolyl)borate adopting an unusual inverted configuration and serves as a bridging ligand for three different sodium ions.