Rhodium, tetrakis[μ-[(αR)-4,5,6,7-tetrachloro-1,3-dihydro-1,3-dioxo-α-tricyclo[3.3.1.13,7]dec-1-yl-2H-isoindole-2-acetato-κO2:κO′2]]di-, (Rh-Rh)