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

Abstract

A dinuclear manganese(III) complex (1) of an N-(carboxymethyl)-N-[3,5-bis(?,?-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 {[Mn2(L)2(OH)(OCH3)][Mn(H2O)3(CH3OH)3], 2, triclinic P[1 with combining macron], a = 13.172(3) ?, b = 15.897(3) ?, c = 19.059(4) ?, V = 3461.9(13) ?3} leading to a trinuclear complex {3, monoclinic P21/n, a = 11.7606(8) ?, b = 21.3505(8) ?, c = 26.7827(17) ?, V = 6722.7(7) ?3} with cyclization of two of the carboxy groups through the doubly-carboxy group coordinated Mn2+ ion. The reaction is discussed in terms of its significance as an illustration of how Mn2+ 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) ?, b = 16.390(8) ?, c = 37.968(19) ?, V = 5856(5) ?3) with different coordinated alcohols could be prepared indicating the potential synthetic uses of this method.