Studies of dirhodium(II) tetra(trifluoroacetate). 5. Remarkable examples of the ambidentate character of dimethyl sulfoxide

The ambidentate character of dimethyl sulfoxide, already known for dirhodiu m carboxylotes, has been remarkably manifested in new ways. Three novel com plexes 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), hav e been obtained by deposition from the vapor phase, and their crystal struc tures have been determined by X-ray crystallography. The crystallographic p arameters 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, alph a = 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) An gstrom, b = 9.017(2) Angstrom, c = 19.841(3) Angstrom, alpha = 101.91(2)4 b eta = 97.144(8)degrees gamma = 100.206(9)degrees, and Z = 1. In the oligome ric molecule of 1, six DMSO ligands bridge seven dirhodium tetra(trifluoroa cetate) 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 als o 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 missi ng in 3, so that two of every three Rh-2(O2CCF3)(4) units are associated th rough the O atoms of carboxylate groups to give the overall composition [Rh -2(O2CCF3)(4)](3)(DMSO)(2).