Structural and spectroscopic studies on three-coordinate complexes of copper(I) halides with tricyclohexylphosphine

Three-coordinate 1 : 1 and 1 : 2 compounds of copper(I) halides with tricyclohexylphosphine have been synthesised and characterized by single crystal X-ray structure determinations, Cu-63 NQR spectroscopy, solid state P-31 CPMAS NMR spectroscopy, and low frequency vibrational spectroscopy. The 1 : 1 compounds crystallize as isomorphous, centrosymmetric [(PCy3)Cu(mu-X)(2)Cu(PCy3)] dimers with three-coordinate (PCuX2) copper. Solid state P-31 CPMAS NMR spectra show asymmetric quartets with the spectra of the chloride and bromide compounds broadened by quadrupole relaxation effects. For X = I, (1)J(P-31-Cu-63) is 1.74 kHz with the quadrupole distortion parameter, dnu(Cu), 11.5 x 10(9) Hz(2). Far infrared spectra of the compounds are unusually complex with groups of strong bands in the region expected for nu(CuX) vibrational modes (100-260 cm(-1)). The 1 : 2 compounds crystallize as [CuX(PCy3)(2)] monomers. The solid state P-31 NMR spectra of the bromide and iodide compounds show sharp asymmetric quartets with (1)J(P-Cu) 1.20 and 1.23 kHz and dnu(Cu) 8.7 and 10.3 x 10(9) Hz(2) respectively. Relaxation effects collapse the spectrum of the chloride to a broad doublet. Room temperature Cu-63 NQR frequencies for [CuX(PCy3)(2)] are found to be 34.5, 33.43 and 32.06 MHz for X = Cl, Br and I respectively and are of the order of 4 MHz greater than values recorded for the 1 : 1 complexes. Far infrared spectra of the complexes exhibit strong bands due to nu(CuX) vibrational modes at 253, 189 and 156 cm(-1) for X = Cl, Br and I.