Enantioselective Synthesis of Optically Active Polymeric Homo- and Bimetallic Oxalate-Bridged Networks [M(2)(ox)(3)](n)().

Abstract

The synthesis of the enantiomeric forms of the two- and three-dimensional polymers: {[NBu(4)][MnCr(ox)(3)]}(n)() (1) (Bu = n-butyl, ox = oxalate), {[M(bpy)(3))][LiCr(ox)(3)]}(n)() (M = Ni (2), Ru (4)) (bpy = 2,2'-bipyridine), {[M(bpy)(3))][Mn(2)(ox)(3)]}(n)() (M = Ni (3), Ru (5)) using resolved [Cr(ox)(3)](3)(-) and [M(bpy)(3)](2+) (M = Ni, Ru) species as chiral building blocks, and their structural characterization are reported. The optical activity of these systems arises from the helical chirality of the tris-chelated subunits with Delta or Lambda configurations. Bimetallic two-dimensional optically active network 1 results from the stacking of similar metallo-oxalate honeycomblike layers containing [Cr(ox)(3)](3)(-) units of the same chirality. The assembly of homochiral species leads to optically active three-dimensional 3-connected 10-gon nets 2-5. Solid state circular dichroism (CD) measurements demonstrate the enantiomeric character of the obtained polymers. Absolute configurations of the metal centers have been assigned according to circular dichroism and X-ray diffraction data. Enantiomerically pure single crystals of the two enantiomeric forms, {[Ru(Delta)(bpy)(3))][Li(Delta)Cr(Delta)(ox)(3)]H(2)O}(n)() (4Delta) and {[Ru(Lambda)(bpy)(3))][Li(Lambda)Cr(Lambda)(ox)(3)]H(2)O}(n)() (4Lambda), have been obtained and the structures determined by X-ray diffraction studies (crystals data: cubic system, space group P2(1)3, a (Å) = 15.293(8) (4Delta), 15.289(2) (4Lambda), Z = 4).