The highly distorted tetrahedral copper(1) complex of the 14-membered trans-N,S, macrocyclic ligand 6,7,15,16-tetrahydrodibenzo[f,m] [I,8 ,4,11 ]dithiadiazacyclotetradecine (L) undergoes reaction with triphenylphosphine to form an adduct in which one of the two sulphur donors of the macrocycle has been displaced from the primary co-ordination sphere of the metal ion, resulting in tetrahedral co-ordination via an N,PS donor array. The triphenylphosphine molecule is labile allowing the parent complex to be recovered upon recrystallization from an acetone-ethanol mixture. Crystal structures of both [CuL] CIO, (1 ) and [CuL( PPh,)] CIO4-0.5Me,CO (2) are reported. For (1): space group P6, a = 17.610(7), c = 5.377(2) A, Z = 3, R = 0.061 for 947 'observed' reflections. For (2): space group PT, a = 15.74(2), b = 12.29(1), c = 9.91 (1 ) A, O! = 82.07(9), p = 84.88(8), y = 84.43(9)", Z = 2, R = 0.1 0 for 1 796 'observed' reflections. The solid-state 31P n.m.r. spectrum for (2) shows a quartet centred on 2.3 p.p.m. with line spacings of 1.41, 1.55, and 1.65 kHz.