p - Tetrahydroborato - bis( bis( triphenylphosphine)- copper(l)] perchlorate, C72H64BClC~Z04 P4, is orthorhombic, space group Pnnb with a = 23.17(l), b = 18.90(l), c = 14.94(l) A, Z =4. The structure was refined to R = 0.045 by fulmla trix least squares using 2203 observed reflections. Two tetrahedral Cu(I) atoms are linked by a tetrahedral BH,- group through bidentate hydrogen bridges, The coordination sphere about each copper is completed by two triphenylphosphines The P-Cu-P angles are distorted /119.7(l) and 124.5(l)']. The former is the smallest angle observed for this type of structure.