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 dirhodium carboxylates, has been remarkably
manifested in new ways. Three novel complexes of dirhodium(II) tetra(trifluoroacetate) with the DMSO ligand,
namely, [Rh2(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 P21/c with a = 28.261(2) Å, b =
16.059(4) Å, c = 17.636(2) Å, β = 92.40(4)°, and Z = 2; for 2, triclinic space group P1̄ with a = 8.915(2) Å,
b = 10.592(2) Å, c = 11.916(2) Å, α = 84.85(1)°, β = 88.86(1)°, γ = 65.187(8)°, and Z = 2; and for 3, triclinic
space group P1̄ with a = 8.876(2) Å, b = 9.017(2) Å, c = 19.841(3) Å, α = 101.91(2)°, β = 97.144(8)°, γ =
100.206(9)°, 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 Rh2(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 μ-DMSO-S,O mode. Every second
DMSO molecule is missing in 3, so that two of every three Rh2(O2CCF3)4 units are associated through the O
atoms of carboxylate groups to give the overall composition [Rh2(O2CCF3)4]3(DMSO)2.