Part 2. Synthesis, characterization and X-ray structure of a new enantiomerically pure bis-equatorial dirhodium(II) compound

The UV irradiation of an acetone solution of Rh2(O2CCF3)4 and the chiral phosphane (1S, 2S, 5R)-(2-hydroxy-5-isopropenyl-2-methyl-cyclohexyl)diphenylphosphane, (+)PPh2(CHR*OH) leads to the formation of two diastereoisomeric bis-equatorial compounds of formula Rh2(μ-O2CCF3)2(η1-O2CCF3)2(η2-(+)PPh2(CHR*OH))2P(+)2 and M(+)2 in a 1.5:1 ratio, respectively. Both compounds have been separated by standard column chromatography. The characterization of the enantiomer M(+)2 has been accomplished by X-ray crystallography. The molecular structure consists of an Rh2 4+ unit bridged by two trifluoroacetate ligands. The coordination of each metal center is fulfilled by one phosphine acting as a chelating equatorial (P atom), an axial (O atom) donor ligand and one monodentate trifluoroacetate providing an (M) configuration. The synthesis, X-ray analysis and a preliminary catalytic assay with M(+)2 are discussed in this note.