Structural and vibrational spectroscopic studies of complexes of trimethylphosphine with copper(I) and silver(I) halides

Abstract

New copper(I) halide–trimethylphosphine adducts were prepared by reaction of CuX with PMe₃ in benzene suspension, and characterized by room-temperature single-crystal X-ray studies and vibrational spectroscopy. [(Me₃P)₂Cu(µ-I)₂Cu(PMe₃)₂], monoclinic, space group P2₁/c, a= 9.296(2), b= 16.206(7), c= 9.577(3)Å, β= 113.76(2)°, Z= 2 dimers, conventional R on |F| 0.040 for 1369 ‘observed’[I > 3σ(I)] reflections at convergence; [{Cu₄Cl₄(PMe₃)₃}_∞], rhombohedral, space group R3c, a= 17.776(2), c= 11.708(7)Å(hexagonal setting), Z= 6, R= 0.045 for 820 observed reflections. The latter is a novel one-dimensional polymer of quasi-cubanoid Cu₄Cl₄ units disposed with their body diagonals coincident with the crystallographic 3-axis and linked by Cu–Cl bonds between the four-co-ordinate apical atoms of successive Cu₄Cl₄ units. Unlike the related [{Cu₄I₄(NEt₃)₃}_∞] polymer, however, the off-axis copper atoms are planar three- rather than four-co-ordinate, having (µ-Cl)₂CuP environments. The far-IR and Raman spectra of the compounds, and of the 1 : 1 Agl–PMe₃ complex with the proposed tetrameric ‘cubane’ structure [Ag₄I₄(PMe₃)₄], have been recorded and assigned. The frequencies and activities of the v(MX) modes correlate well with the observed or proposed structures, and a comparison of the Raman spectra for the series of three compounds allows the first rational assignment of v(MP) modes for multinuclear complexes of this type.