Enantioselective synthesis of optically active polymeric homo- and bimetallic oxalate-bridged networks [M-2(ox)(3)](n)

The synthesis of the enantiomeric forms of the two- and three-dimensional p olymers: {[NBu4] [MnCr(ox)(3)]}(n) (1) (Bu = n-butyl, ox = oxalate), {[M(bp y)(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 th ese 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 honey comblike 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) measureme nts demonstrate the enantiomeric character of the obtained polymers. Absolu te configurations of the metal centers have been assigned according to circ ular dichroism and X-ray diffraction data. Enantiomerically pure single cry stals of the two enantiomeric forms, ([Ru-Delta(bpy)(3))][LiDeltaCrDelta(ox )(3)]H2O}(n) (4 Delta) and {[Ru-Lambda(bpy)(3))][LiLambdaCrLambda(ox)(3)]H2 O}(n) (4 Lambda), have been obtained and the structures determined by X-ray diffraction studies (crystals data: cubic system, space group P2(1)3, a (A ngstrom) = 15.293(8) (4 Delta), 15.289(2) (4 Lambda), Z = 4).