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

Crystal structures of organometallic aqua complexes [Cp*Rh-III(bpy)(OH2)](2+) (1, Cp* = eta(5)-CsMe5, bpy = 2,2'-bipyridine) and [Cp*Rh-III(6,6'-Me(2)bpy)(OH2)](2+) (2, 6,6'-Me(2)bpy = 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) angstrom obtained for 1(PF6)(2) is Significantly different from that of 2.157(3) A obtained for the previously reported disorder model [Cp*Rh-III(bpy)(0.7H(2)O/0.3CH(3)OH)](CF3SO3)(2)center dot 0.7H(2)O in which the coordinated water is replaced by a coordinated methanol. The five-membered ring involving the Rh atom and the 6,6'-Me(2)bpy 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'-Me(2)bpy ligand and the Cp* ligand. Copyright (c) 2005 John Wiley C Sons, Ltd.