Structural and spectroscopic studies on three- and two-co-ordinate copper(I) halide tribenzylphosphine complexes

Abstract

Three-co-ordinate, monomeric 1∶2 complexes of tribenzylphosphine (PBz₃) with copper(I) halides, [Cu(PBz₃)₂X] (X = Cl, Br or I), have been synthesized and characterized by single crystal structure determinations, solid state ³¹P CPMAS NMR spectroscopy and low frequency vibrational spectroscopy. The two PBz₃ ligands show different conformational structures and this is reflected in a distorted ‘P₂CuX’ geometry for each complex. Solid state ³¹P CPMAS spectra show asymmetric quartets with ¹J(³¹P–⁶³Cu) ranging from 1.23 to 1.46 kHz and asymmetry parameters, dν_Cu, ranging from 8 × 10⁹ to 13 × 10⁹ Hz². Reported also are the synthesis, structure, solid state ³¹P NMR and far-IR spectra of the two-co-ordinate complex [Cu(PBz₃)₂][CuCl₂] and the crystal structure of the dimeric 1∶1 chloride complex, [Cu₂(PBz₃)₂Cl₂]·3C₆H₆, this latter structure being the first of this type reported for the PBz₃ ligand. Attempts to synthesize a 1∶1 chloro complex using acetonitrile, rather than chloroform, as solvent led to the formation of tribenzylphosphine oxide. The conversion of [Cu₂(PBz₃)₂Cl₂]·3C₆H₆ into [Cu(PBz₃)₂][CuCl₂] upon removal of benzene of solvation was followed by far-IR spectroscopy. The vibrational spectra of the bulk 1∶1 and 1∶2 complexes are consistent with the crystal structures. Bands due to the ν(CuX) modes of the neutral complexes and those due to the [CuX₂]⁻ ions in the ionic complexes have been assigned, and the relationship between the spectra and the structures of the compounds is discussed.

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