Thermal decomposition of a thiolatocopper(ii) complex Cu(SCPh(3))(HB(3,5-Pr(2)(i)pz)(3)) 1 yields a novel mu-eta(2):eta(2)-disulfide dinuclear copper(ll) complex (Cu[HB(3,5-Pr(2)(i)pz)(3)]),(S-2) 2 whose crystal structure was determined by X-ray crystallography.