Exocyclic coordination chemistry of an O2S2-macrocycle with copper(i), mercury(ii) and palladium(ii) ions

Abstract

The preparation and structures of the exocyclic coordination-based supramolecular complexes of a 14-membered dibenzo-O₂S₂-macrocycle, L, with thiaphilic soft metal ions Cu(I), Hg(II) and Pd(II) are reported. The X-ray crystal structures of the eight complexes have been determined, and a range of the less common structural types, including mono- and multinuclear species with discrete and infinite forms were obtained. L reacts with copper(I) halides and afforded isostructural complexes of type [(Cu₂X₂)L]_n (1: X = Cl, 2: X = Br) adopting a two-dimensional (2-D) polymeric structure linked by square-type Cu₂X₂ clusters, while copper(I) iodide gave a yellow emissive complex {[(Cu₄I₄)L₂]·2.5H₂O}_n (3) whose crystal structure was not available. Treatment of L with copper(I) thiocyanate gave an infinite 2-D coordination network [CuLSCN]_n (4) in which copper atoms are linked by SCN⁻ forming a 1-D backbone, then further cross-linked by Lvia Cu–S bonds resulting in a grid-type layered structure. Reactions of L with HgX₂ (X = Br and I) resulted in the formation of an interesting “ivy-leaves” shaped complex [HgLBr₂]_n (5) with a syndiotactic arrangement and a single-stranded complex [(Hg₂I₄)L]_n (6), respectively, adopting an infinite 1-D structure. Unlike the copper(I) and mercury(II) complexes with the infinite structures, reactions of L with Pd(NO₃)₂ gave a 1 : 1 (metal-to-ligand) dinitrato complex cis-[PdL(NO₃)₂] (7) and a 1 : 2 bis(macrocycle) complex cis-[PdL₂](NO₃)₂ (8) in a discrete form depending on the molar ratio of the reactants. A straightforward one-pot reaction of Pd(NO₃)₂ with two equivalents of L also resulted in the isolation of the bis(macrocycle) complex 8. The comparative NMR and ESI-mass studies for the palladium(II) complexes were also carried out. The results are discussed in terms of the exo-coordination modes as well as the anion coordination.