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

Abstract

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, 63Cu NQR spectroscopy, solid state 31P CPMAS NMR spectroscopy, and low frequency vibrational spectroscopy. The 1 ∶ 1 compounds crystallize as isomorphous, centrosymmetric [(PCy3)Cu(μ-X)2Cu(PCy3)] dimers with three-coordinate (PCuX2) copper. Solid state 31P CPMAS NMR spectra show asymmetric quartets with the spectra of the chloride and bromide compounds broadened by quadrupole relaxation effects. For X = I, 1J(31P–63Cu) is 1.74 kHz with the quadrupole distortion parameter, dνCu, 11.5 × 109 Hz2. Far infrared spectra of the compounds are unusually complex with groups of strong bands in the region expected for ν(CuX) vibrational modes (100–260 cm−1). The 1 ∶ 2 compounds crystallize as [CuX(PCy3)2] monomers. The solid state 31P NMR spectra of the bromide and iodide compounds show sharp asymmetric quartets with 1J(P–Cu) 1.20 and 1.23 kHz and dνCu 8.7 and 10.3 × 109 Hz2 respectively. Relaxation effects collapse the spectrum of the chloride to a broad doublet. Room temperature 63Cu 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 ν(CuX) vibrational modes at 253, 189 and 156 cm−1 for X = Cl, Br and I.