Key indicators: single-crystal X-ray study; T = 90 K, P = 0.0 kPa; mean (C-C) = 0.003 Å; R factor = 0.032; wR factor = 0.077; data-to-parameter ratio = 24.3.In the title solvate, [Rh 2 (C 22 (2) and 2.090 (2) Å ], and one COD ligand via two 2 -bonds, each directed toward the mid-point of a C C bond (Cg): Rh-Cg = 2.007 (2), 2.013 (2), 2.000 (2) and 2.021 (2) Å . Each Rh I atom has a quasi-square-planar coordination geometry, with average r.m.s. deviations of 0.159 (1) and 0.204 (1) Å from the mean planes defined by Rh and the termini of its four coordinating bonds. The two COD ligands have quasi-C 2 symmetry, twisted from ideal C 2v symmetry by 30.0 (3) and À33.1 (3) , and are quasi-enantiomers of one another. The intramolecular RhÁ Á ÁRh distance of 5.9432 (3) Å suggests that there is no direct metal-metal interaction. Related literature