Crystal and molecular structures of di-µ-acetato-OO′-bis[acetato-OO′)-methylrhenium(III)](4Re–Re) and di-µ-acetato-OO′-bis[chloro(methyl)rhenium(III)](4Re–Re)–dimethyl sulphoxide (1/1)

Abstract

The crystal structures of the title compounds, denoted (A) and (B) respectively, have been determined by single-crystal X-ray analysis. Compound (A) is monoclinic, space group C2/c with a= 17.102, b= 6.567, c= 14.724 Å, β= 105.56°, and Z= 4. The structure has been refined to an R value of 0.039 using 1 681 observed [I > 1.5σ(I)] intensities measured on an automatic diffractometer. The centrosymmetric molecule contains two bridging and two chelating acetate groups. One oxygen atom from each chelating acetate group lies along the Re–Re axis at a distance of 2.462 Å. In spite of the two axially co-ordinated ligands, the Re[graphic omitted]Re distance [2.177(1)Å] is equal to the shortest Re–Re distance yet recorded. Compound (B) is triclinic, space group P, with a= 7.382. b= 11.259, c= 10.891 Å, α= 94.69, β= 109.87, γ= 73.56°, and Z= 2. The structure has been refined to an R value of 0.035 using 3 936 observed intensities. This molecule also contains two bridging acetate groups in a mutually trans arrangement, but the axial–equatorial chelating acetates have now been replaced by equatorially bonded chloride ligands with just one of the rhenium atoms carrying an axial ligand, a dimethyl sulphoxide molecule co-ordinated via its oxygen atom (Re–O 2.302 Å). The Re–Re distance in this molecule is longer than in (A), but at 2.184 Å it is still very short.