N-hydroxymethylation of ethylene-bridged glycine metal(II) complexes by formaldehyde

The (N,N'-ethylenediglycinato)metal(II) complexes, M(edg) (M = Cu, Zn, Ni, Co) undergo N-hydroxymethylation with formaldehyde in the pH range similar to3.5-9.5 to yield the respective [N,N'-ethylenedi(N-hydroxymethyl-glycinato)]metal(II), ML x H2O (L = N,N'-ethylenedi(N-hydroxymethylglycinate); x = 4, 4.5). The crystal and molecular structures of the Ni(edg) 3H(2)O and ML 4H(2)O (M = Ni, Cu, Co) complexes have been determined; all the complexes have distorted octahedral geometries and their tetradentate ligands have oc-cis configuration. Analysis of these structures also shows that the N-hydroxymethylated ligands are stereospecifically coordinated. However, M(edg) do not undergo Mannich ammomethylation with formaldehyde and ammonia. In the reactions studied, the alpha-carbon of M(edg) is unaffected by formaldehyde attack. No further condensation of the N-hydroxymethyl substituents and their potential reactivity are also explained. (C) 2002 Elsevier Science B.V. All rights reserved.