Table 1. Metal–metal distances (Å) in complexes 1–4 .

Compound	Cu—Cu distance
Complex 1	2.7173 (7)
Complex 2	2.657 (3) and 2.669 (3)
Complex 3	2.6571 (6) and 2.6685 (6)
Complex 4	2.6469 (7) and 2.6592 (8)

Compounds 2–4 each contain two crystallographically independent clusters.