Bright Cyan Phosphorescence of a (Phosphane)copper(I) Complex of the Tri­hydrido­pyrazolylborate Ligand H3B(3,5‐Ph2Pz)–

Abstract

AbstractThe ligand trihydrido(3,5‐diphenylpyrazol‐1‐yl)borate([MpPh2]–) has been synthesized from 3,5‐diphenylpyrazole and sodium borohydride in N,N‐dimethylformamide. By using this ligand, three phosphane‐stabilized copper(I) complexes [Cu(MpPh2)(L2)] [L2 = (PPh3)2, 1,2‐bis(diphenylphosphanyl)ethane (dppe), or 1,2‐bis(diphenylphosphanyl)benzene (dppbz)] were synthesized. The complexes were characterized by multinuclear NMR spectroscopy, IR spectroscopy, and X‐ray crystallography. The crystal structures of these complexes show that the copper ions are in trigonal‐pyramidal geometries with the apical position formed by agostic Cu–H interactions between the CuI center and one of the hydride atoms of the borate ligand. Complexes [Cu(MpPh2)(PPh3)2] and [Cu(MpPh2)(dppbz)] are mononuclear, whereas complex [Cu2(MpPh2)2(μ‐dppe)2] is dinuclear with bridging dppe ligands. In the solid state, fluorescent emissions are observed in [Cu(MpPh2)(PPh3)2] and [Cu2(MpPh2)2(μ‐dppe)2] but not in [Cu(MpPh2)(dppbz)], which exhibits bright cyan phosphorescence at room temperature that shifts to green when the sample is cooled to 77 K. The phosphorescence of [Cu(MpPh2)(dppbz)] is attributed to mixed interligand and metal‐to‐ligand charge transfer 3(MLCT + π–π*) excited states.