While the reaction of the monophosphaalkene [(2,4,6-tri-tert-butylphenyl)phosphanediylmethyl]-benzene (L2) with copper(I) chloride led to a dimeric complex [Cu2Cl2L22(NCMe)2]1, use of the diphosphaalkene 1,3-bis[(2,4,6-tri-tert-butylphenyl)phosphanediylmethyl]benzene (L1) gave rise to a tetrameric complex [Cu4Cl4L12]·3EtOH 2. The crystal structures of the complexes have been determined and indicate that 1 is a centrosymmetric dimer with tetrahedrally co-ordinated copper(I) centres, whereas 2 adopts a cubane-like structure with pairs of copper atoms bridged by different L1 units.