Three-co-ordinate, monomeric 12 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, dCu, ranging from 8 נ109 to 13 נ109 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 11 chloride complex, [Cu2(PBz3)2Cl2]糃6H6, this latter structure being the first of this type reported for the PBz3 ligand. Attempts to synthesize a 11 chloro complex using acetonitrile, rather than chloroform, as solvent led to the formation of tribenzylphosphine oxide. The conversion of [Cu2(PBz3)2Cl2]糃6H6 into [Cu(PBz3)2][CuCl2] upon removal of benzene of solvation was followed by far-IR spectroscopy. The vibrational spectra of the bulk 11 and 12 complexes are consistent with the crystal structures. Bands due to the (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.