Cu(I) Complexes of Multidentate and Carbodiphosphorane Ligands and Their Photoluminescence.

A series of dinuclear copper(I) and carbodiphosphorane (CDP) complexes using multidentate ligands CDP(Py) () and (CDP(CHPPh) () have been isolated and characterized. Detailed structural information was gained by single-crystal XRD analyses of nine representative examples. The common structural motive is the central double ylidic carbon atom with its characteristic two lone pairs involved in the binding of two geminal L-Cu(I) fragments at Cu-Cu distances in the range 2.55-2.67 Å. In order to enhance conformational rigidity within the characteristic Cu-C-Cu triangle, two types of chelating side arms were symmetrically attached to each phosphorus atom: two 2-pyridyl functions in ligand CDP(Py) () and its dinuclear copper complexes and , as well as two diphenylphosphinomethylene functions in ligand CDP(CHPPh) () and its di- and mononuclear complexes -. Neutral complexes were typically obtained via the reaction of with Cu(I) species CuCl, CuI, and CuSPh or via the salt elimination reaction of [(CuCl)(CDP(Py)] () with sodium carbazolate. Cationic Cu(I) complexes were prepared upon treating with two equivalents of [Cu(NCMe)]PF, followed by the addition of either two equivalents of an aryl phosphine (PPh P(CHOMe)) or one equivalent of bisphosphine ligands bis[(2-diphenylphosphino)phenyl] ether (DPEPhos), 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (XantPhos), or 1,1'-bis(diphenyl-phosphino) ferrocene (dppf). For the first time, carbodiphosphorane CDP(CHPPh) () could be isolated upon treating its precursor [CH(dppm)]Cl () with NaNH in liquid NH. A protonated and a deprotonated derivative of ligand were prepared, and their coordination was compared to neutral CDP ligand . NMR analysis and DFT calculations reveal that the most stable tautomer of does not show a CDP (or carbone) structure in its uncoordinated base form. For most of the prepared complexes, photoluminescence upon irradiation with UV light at room temperature was observed. Quantum yields () were determined to be 36% for dicationic (CuPPh)(CDP(Py)) () and 60% for neutral [(CuSPh)(CDP(CHPPh)] ().