Cadmium(II) and mercury(II) complexes of an NO2S2-donor macrocycle and its ditopic xylyl-bridged analogue

Abstract

The NO2S2-donor macrocycle (L-1) was synthesised from the ring closure reaction between Boc-N-protected 2,2'-iminobis(ethanethiol) (3) and 2,2- (ethylenedioxy) bis(benzyl chloride) (4) followed by deprotection of the Boc-group. alpha,alpha'-Dibromo-p-xylene was employed as a dialkylating agent to bridge two L-1 to yield the corresponding N-linked product (L-2). The X-ray structure of L-2 (as its HBr salt) is described. A range of Cd(II) and Hg(II) complexes of L-1 (6-9) and L-2 (10-12) were prepared and characterised. Reaction of HgX2 (X = Br or I) with L-1 afforded [Hg(L-1) Br](2) [Hg2Br6] . 2CH(2)Cl(2) 6 and [Hg(L-1) I-2] 7, respectively. For 6, the Hg(II) ion in the complex cation has a distorted tetrahedral coordination environment composed of S2N donor atoms from L-1 and a bromo ligand. In 7 the coordination geometry is highly distorted tetrahedral, with the macrocycle coordinating in an exodentate manner via one S and one N atom. The remaining two coordination sites are occupied by iodide ions. [Hg(L-1) (ClO4)] ClO4 8 was isolated from the reaction of Hg(ClO4)(2) and L-1. The X-ray structure reveals that all macrocyclic ring donors bind to the central mercury ion in this case, with the latter exhibiting a highly distorted octahedral coordination geometry. The O2S2-donors from the macrocyclic ring de ne the equatorial plane while the axial positions are occupied by the ring nitrogen as well as by an oxygen from a monodentate perchlorato ion. Reaction of Cd(NO3)(2) . 4H(2)O with L-1 afforded [Cd(L-1) (NO3)(2)] . 0.5CH(2)Cl(2) 9 in which L-1 acts as a tridentate ligand, binding exo-fashion via its S2N donors. The remaining coordination positions are filled by two bidentate nitrate ions such that, overall, the cadmium is seven-coordinate. Reactions of HgX2 (X = Br or I) with L-2 yielded the isostructural 2 : 1 (metal : ligand) complexes, [Hg-2(L-2) Br-4] 10 and [Hg-2(L-2)I-4] 11. Each mercury ion has a distorted tetrahedral environment made up of S and N donors from an exodentate L-2 and two coordinated halides. Contrasting with this, the reaction of L-2 with Cd(NO3)(2) . 4H(2)O yielded a 1-D coordination network, {[Cd-2(L-2) (NO3)(4)] . 2CH(2)Cl(2)}(n) 12 in which each ring of L-2 is exo-coordinated via two S atoms and one N atom to a cadmium ion which is also bound to one monodentate and one bidentate nitrate anion. The latter also has one of its oxygen atom attached to a neighboring cadmium via a nitroso (mu(2)-O) bridge such that the overall coordination geometry about each cadmium is seven-coordinate. The [Cd(L-2)(0.5)(NO3)(2)] units are linked by an inversion to yield the polymeric arrangement.