STEREOSPECIFIC AND REGIOSPECIFIC CONVERSIONS OF RH2X6(PR3)3 MOLECULESTO RH2X6(PR3)4 AND RHX3(PR3)3 MOLECULES

Studies by P-31 NMR spectroscopy have shown that the face-sharing bioc tahedral molecules Rh2X6(PR3)3 (X = Cl, Br; PR3 = PEt3, PPr3, PBu3) ex ist exclusively as the 1,2,6-isomers and are converted by addition of 1 molar equiv of PR'3 (R' may be R) exclusively to the 1,3,6,8-Rh2X6(P R3)3(PR'3) isomer, with the entering PR'3 occupying the 6-(or 8-) posi tion. Moreover, the edge-sharing 1,3,6,8-Rh2X6(PR3)4 type molecules re act further with trialkylphosphine to produce exclusively mer-RhX3(PR3 )3 products, even though, as is also demonstrated, the fac-RhX3(PR3)3 isomers are thermodynamically preferred.