Bright Cyan Phosphorescence of a (Phosphane)copper(I) Complex of the Tri-hydrido-pyrazolylborate Ligand H sub(3)B(3,5-Ph sub(2)Pz) super(-)

The ligand trihydrido(3,5-diphenylpyrazol-1-yl)borate([Mp super(Ph2)] super()- 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 super(Ph2))(L sub(2))] [L sub(2) = (PPh sub(3)) sub(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 super(I) center and one of the hydride atoms of the borate ligand. Complexes [Cu(Mp super(Ph2))(PPh sub(3)) sub(2)] and [Cu(Mp super(Ph2))(dppbz)] are mononuclear, whereas complex [Cu sub(2)(Mp super(Ph2)) sub(2)( mu -dppe) sub(2)] is dinuclear with bridging dppe ligands. In the solid state, fluorescent emissions are observed in [Cu(Mp super(Ph2))(PPh sub(3)) sub(2)] and [Cu sub(2)(Mp super(Ph2)) sub(2)( mu -dppe) sub(2)] but not in [Cu(Mp super(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 super(Ph2))(dppbz)] is attributed to mixed interligand and metal-to-ligand charge transfer super(3)(MLCT + pi - pi *) excited states. Reaction of (diphosphane)(halido)copper(I) complexes with trihydrido(3,5-diphenylpyrazolyl)borate results in the formation of heteroleptic complexes that exhibit interesting luminescent properties and structural features such as pronounced agostic Cu...HB interactions.