Syntheses, structures, and stereospecific FSBO/ESBO/MONO interconversions of rhodium(III) phosphine complexes

Abstract

Several face-sharing rhodium(III) dinuclear compounds have been synthesized and structurally characterized. These include the preparation and x-ray crystal structures of Rh2X6(PR3)3, (x = Cl, Br ; PR3 = Pet3, PPR^n3). All of the Rh2X6P3 complexes have the 1,5,6 ligand arrangements. The FSBO/ESBO/MONO interconversions of 1,5,6 ligand arrangements. The FSBO/ESBO/MONO interconversions of 1,5,6- Rh2X6P3 have been studied by the 31P(1H) NMR spectroscopic method. A solution of 1,5,6-Rh2X6P3 shows no tendency to isomerize at or below room temperature, and, upon treatment with slightly more than on molar equivalent of phosphine is converted exclusively to the 1,3,6,8- Rh2X6P3P;. when the 1,3,6,8-Rh2X6P4 compounds are heated under vacuum, 1,5,6-Rh2X6P3 is re-formed quantitatively and exclusively. The addition of slightly more than two equivalents of phosphine to 1,3,6,8-Rh2X6P4 produces quantitatively and exclusively the mer-RhX3(PR3)3. Several 1,5-Rh2X7(Pet3)2 ( = cl and Br) anionic complexes have been synthesized and structurally characterized. These include the preparation and x-ray crystal structures of [PPh4][1,5-Rh2Cl7(Pet3)2], [Y][1,5-Rh2Br7(Pet3)2] (Y = Net4 and PPh4). The FSBO/ESBO interconversions of these Rh2X7(Pet3)2 anions have also been studied by the 31;(1H) NMR spectroscopic method. In solution the 1,5-Rh2X7(Pet3)2 anion shows no tendency to isomerize at or below room temperature, and, upon treatment of one molar equivalent of phosphine, is converted exclusively to the 1,6,8-Rh2X7(Pet3)2(PR3) anion...