Dark and photochemical reactions of Co3Rh(CO)12 with diphenylacetylene yield two butterfly clusters with the alkyne inserted into the tetrametal framework. One of them is the previously unknown cluster Co3Rh(μ - CO)2(CO)8(μ4,η2, - PhC2Ph). It was characterized by X-ray crystallography (dark violet compound crystallizing in monoclinic space group C2/c, a = 15.665(2), b = 17.947(5), c = 9.078(1) Å, β = 93.91(1)°, v = 2546.1(8) Å3, Z = 4). The 13C NMR study showed that the solid state structure is retained in solution. The second product is the Co2Rh2(μ - CO)2(CO)8(μ4,η2 - PhC2Ph) cluster obtained earlier and identified herein by its 13C NMR spectrum. The formation of this cluster is evidently caused by bimolecular metal-metal exchange between cluster molecules in the course of the reaction. © 1994.