Synthesis, Electronic Spectra and Solvent-Induced Reversible Dissociation of Diphosphine(hexafluoroacetylacetonato)copper(I) Complexes

The complexes Cu (P-P)(hfac) with P-P = 1,2-bis(diphenylphosphino)ethane (diphos), 1,3-bis-(diphenylphosphino)propane (prophos), 2,2’-bis(diphenylphosphino)-1,1’-binaphthyl (binap) and hfac = hexafluoroacetylacetonate were synthesized and spectroscopically characterized. In the solid state or in solutions of non-polar solvents these compounds are yellow owing to a long-wavelength (hfac →P-P) ligand-to-ligand charge transfer absorption. In coordinating solvents such as CH CN the complexes undergo a reversible dissociation according to the equation: Cu(P-P)(hfac) + n CH CN ⇌ [Cu(P-P)(CH CN) hfac While the complexes are not luminescent the ion pairs [Cu(P-P)(CH CN) hfac are emissive at 77 K. The cations and the anions show separate emissions as indicated by the excitation spectra.