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

The ligand trihydrido(3,5-diphenylpyrazol-1-yl) borate([ Mp(Ph2)](-)) 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(Mp(Ph2))(L-2)] [L-2 = (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 Cu-I center and one of the hydride atoms of the borate ligand. Complexes [Cu-(Mp(Ph2))(PPh3)(2)] and [Cu(Mp(Ph2))(dppbz)] are mononuclear, whereas complex [Cu-2(Mp(Ph2))(2)(mu-dppe)(2)] is dinuclear with bridging dppe ligands. In the solid state, fluorescent emissions are observed in [Cu(Mp(Ph2))(PPh3)(2)] and [Cu-2(Mp(Ph2))(2)(mu-dppe)(2)] but not in [Cu(Mp(Ph2))(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(Mp(Ph2))(dppbz)] is attributed to mixed interligand and metal-to-ligand charge transfer (3)(MLCT + pi-pi*) excited states.