Crystallographic report: Crystal structures of organometallic aqua complexes [Cp*RhIII(bpy)(OH2)]2+ and [Cp*RhIII(6,6′-Me2bpy)(OH2)]2+ used as key catalysts in regioselective reduction of NAD+ analogues

Abstract

Crystal structures of organometallic aqua complexes [Cp*RhIII(bpy)(OH2)]2+ (1, Cp* = η5-C5Me5, bpy = 2,2′-bipyridine) and [Cp*RhIII(6,6′-Me2bpy)(OH2)]2+ (2, 6,6′-Me2bpy = 6,6′-dimethyl-2,2′-bipyridine) used as key catalysts in regioselective reduction of NAD+ analogues were determined definitely by X-ray analysis. The yellow crystals of 1(PF6)2 and orange crystals of 2(CF3SO3)2 used in the X-ray analysis were obtained from aqueous solutions of 1(PF6)2 and 2(CF3SO3)2. The Rh–Oaqua length of 2.194(4) Å obtained for 1(PF6)2 is significantly different from that of 2.157(3) Å obtained for the previously reported disorder model [Cp*RhIII(bpy)(0.7H2O/0.3CH3OH)](CF3SO3)2·0.7H2O in which the coordinated water is replaced by a coordinated methanol. The five-membered ring involving the Rh atom and the 6,6′-Me2bpy chelating unit in 2(CF3SO3)2 is not flat, whereas the five-membered chelate ring in 1(PF6)2 is nearly flat. Such a non-planar structure in 2(CF3SO3)2 is ascribed to the steric repulsion between the 6,6′-Me2bpy ligand and the Cp* ligand. Copyright © 2005 John Wiley & Sons, Ltd.