Lead(II) and barium(II) complexes of a potentially octadentate macrocyclic ligand (H4L), capable of providing endogenous alkoxy and phenoxy bridges. The X-ray crystal structures of [Pb(H4L)][ClO4]2, [Pb2(H2L)][ClO4]2, and [(H6L)(H2O)2][ClO4]2

Abstract

Condensation of 2,6-diformyl-4-methylphenol with 1,3-diamino-2-hydroxypropane in the presence of Pb(ClO₄)₂·6H₂O resulted in the sequential formation of three products which have been characterised by X-ray crystallography as mononuclear [Pb(H₄L)][ClO₄]₂(1), binuclear [Pb₂(H₂L)][ClO₄]₂(2), and a diaquo complex of the partly protonated macrocycle [(H₆L)(H₂O)₂][ClO₄]₂(3)(where H₄L is a 20-membered, potentially octadentate, macrocyclic ligand, with an N₄O₄ donor set which is capable of providing endogenous phenoxy and alkoxy bridges). The use of Pb(NCS)₂ as a template agent, gave only the mononuclear complex [Pb(H₄L)(NCS)₂]·2H₂O (4), under all conditions investigated. Similarly when Ba(ClO₄)₂·6H₂O or Ba(NCS)₂·H₂O were used the only products were the mononuclear complexes [Ba(H₄L)X₂]·yH₂O [(5), X = NCS, y= 2; and (6), X = ClO₄, y= 1). These complexes were characterised by microanalysis, i.r., and ¹H and ¹³C n.m.r. spectra. The mononuclear lead and barium complexes have been shown to have distinctly different co-ordination and this is ascribed to the relative sizes of the ions concerned.