The compounds, [(PPh3)4Cu] ClO4, (I), [(CH3CN)( PPh3)2 Cu] ClO4, (2), and [(CH3CN)2(PPh3)2Cu]-ClO4, (3) ( PPh3 = triphenylphosphine ), have been characterized by solid-state 31P n.m.r . spectroscopy and crystal structure analysis. Crystals of (2) are orthorhombic, Pcab , a 24.506(9), b 22.49(1), c 17.905(8) ?, Z = 8; R was 0.089 for 2178 independent 'observed' reflections. Crystals of (3) are monoclinic, P21/n, a 15.506(6), b 26.98(1), c 9.220(3) ?, ߠ94.70(3)ଠZ = 4; R was 0.070 for 2622 independent reflections. In both cations, the copper(:) atom is four-coordinate by the phosphine and acetonitrile ligands . In (2), Cu-P are 2.321(5)-2.338(5) ?, with Cu-N, 2.11(1) ?; N-Cu-P lie between 100.1(3) and 106.0(3)ଠwhile P-Cu-P range from 113.0(2) to 119.3(2)஠In (3), Cu-P are 2.257(3), 2.278(3) and Cu-N, 2.068(8) and 2.020(8) ?; with P-Cu-P, 127.6(1), N-Cu-N, 99.2(3), and P-Cu-N, 101.7(2)-109.9(3)஠Solid state 31P n.m.r . spectra of (1), (2) and (3) show one, three and two sets of overlapping quartets respectively. The average chemical shift data for each quartet with respect to 85% phosphoric acid is: (1)-5.0ppm; (2)2.6, 1.2, -0.6 ppm ; (3) 4.0,-3.0 ppm [cf. free PPh3 in the solid state, -9.9 ppm ]. The magnitude, ?vi, and asymmetry, Avvij, of the splitting between the peaks of each quartet is consistent with a distorted tetrahedral environment for the three compounds. Infrared spectroscopic, differential scanning calorimetric, solid state 31P n.m.r . and powder XRD measurements show that heating of (2) and (3) leads to the desolvated complexes, [(PPh3)3CuClO4], (4), and [(PPh3)2CuClO4], (5), in which the perchlorate anions function as monodentate and bidentate ligands respectively.