Ligand displacement for fixing manganese: relevance to cellular metal ion transport and synthesis of polymeric coordination complexes.

A dinuclear manganese(III) complex (1) of an N-(carboxymethyl)-N-[3,5-bis(α,α-dimethylbenzyl-2-hydroxybenzyl)]glycine (HDA) ligand (L) binds a manganese(II) species through displacement of its solvating ligands by appropriately dispositioned carbonyl groups of a dinuclear complex {[Mn(2)(L)(2)(OH)(OCH(3))][Mn(H(2)O)(3)(CH(3)OH)(3)], 2, triclinic P1, a = 13.172(3) Å, b = 15.897(3) Å, c = 19.059(4) Å, V = 3461.9(13) Å(3)} leading to a trinuclear complex {3, monoclinic P21/n, a = 11.7606(8) Å, b = 21.3505(8) Å, c = 26.7827(17) Å, V = 6722.7(7) Å(3)} with cyclization of two of the carboxy groups through the doubly-carboxy group coordinated Mn(2+) ion. The reaction is discussed in terms of its significance as an illustration of how Mn(2+) ions might be sequestered in biological systems. A similar solvato-ligand displacement reaction was used to synthesise coordination polymers of an HDA iron(III) complex involving polymerization through a bridging carboxylato group. Several isostructural polymers (5-7; for 5: orthorhombic Pbca, a = 9.411(5) Å, b = 16.390(8) Å, c = 37.968(19) Å, V = 5856(5) Å(3)) with different coordinated alcohols could be prepared indicating the potential synthetic uses of this method.