Mixed base pyridine (py)/triphenylphosphine adducts of the copper(1) halides, CuX, have been synthesized for 1 : 1 : 1 stoichiometry for X = chloride and iodide; single-crystal X-ray structure determinations of these show them to be isomorphous and isostructural with that of the bromide recorded elsewhere, being µ,µ′- dihalo-bridged dimers , [(PPh₃)( py )CuX₂Cu( py )(PPh₃)], monoclinic, C2/c, a ≈ 26.2, b ≈ 14.3, c ≈ 11 .2 Å , β ≈ 95, Z = 4 dimers. The bromide has been isolated as a new monoclinic C 2/m polymorph, a 11 .279(8), b 14.268(6), c 13.858(4) Å, β 109.33(6)º, Z=4 dimers, and details of its structure are also recorded. The structures of their pyridine-4-carbonitrile (pycn) analogues have also been determined and found to be also binuclear, with no cyano-copper interactions; these also are an isomorphous, isostructural series, monoclinic P2₁/n, a ≈ 15.4, b ≈ 8.1, c ≈ 17.9 Å , β ≈ 101 º, Z = 2 dimers. In each series of dimers, one half of the dimer is crystallographically independent, the generators of the other half being twofold rotor (C₂/c phase), mirror (C₂/m phase) and inversion centre (P2₁/n phase) respectively.