The ambidentate character of dimethyl sulfoxide, already known for dirhodium carboxylotes, has been remarkably manifested in new ways. Three novel complexes of dirhodium(II) tetra(trinuoroacetate) with the DMSO ligand, namely, [Rh-2(O2CCF3)(4)]m(DMSO)(n) With m:n = 7:8 (1), 1:1 (2), and 3:2 (3), have been obtained by deposition from the vapor phase, and their crystal structures have been determined by X-ray crystallography. The crystallographic parameters are as follows: for 1, monoclinic space group P2(1)/c with a = 28.261(2) Angstrom, b = 16.059(4) Angstrom, c = 17.636(2) Angstrom, beta = 92.40(4)degrees, and Z = 2; for 2, triclinic space group P (1) over bar with a = 8.915(2) Angstrom, b = 10.592(2) Angstrom, c = 11.916(2) Angstrom, alpha = 84.85(1)degrees, beta = 88.86(1)degrees, gamma = 65.187(8)degrees, and Z = 2; and for 3, triclinic space group P (1) over bar with a = 8.876(2) Angstrom, b = 9.017(2) Angstrom, c = 19.841(3) Angstrom, alpha = 101.91(2)4 beta = 97.144(8)degrees gamma = 100.206(9)degrees, and Z = 1. In the oligomeric molecule of 1, six DMSO ligands bridge seven dirhodium tetra(trifluoroacetate) units in a bidentate fashion via S and O atoms, and two additional DMSO molecules terminate the chain. In the structure of the monoadduct Rh-2(O2CCF3)(4)(DMSO) (2), the dirhodium blocks are bridged through the O atoms of DMSO ligands, forming a one-dimensional polymeric chain. Compound 3 also has an infinite chain structure with the molecules of dimethyl sulfoxide acting in a bidentate mu-DMSO-S,O mode. Every second DMSO molecule is missing in 3, so that two of every three Rh-2(O2CCF3)(4) units are associated through the O atoms of carboxylate groups to give the overall composition [Rh-2(O2CCF3)(4)](3)(DMSO)(2).