Preparation, stereochemistry, and crystal structures of some complexes of the macrocycle 3,3,7,7,11,11,15,15-octamethyl-1,9-dithia-5,13-diazacyclohexadecane with CoII, NiII, CuI, CuII, ZnII, RhIII, AgI, CdII, PtII, and HgII salts

Abstract

The preparation of some complexes of the macrocycle 3,3,7,7,11,11,15,15-octamethyl-1,9-dithia-5,13-diazacyclohexadecane (L) with Co^II, Ni^II, Cu^I, Cu^II, Zn^II, Rh^III, Ag^I, Cd^II, Pt^II, and Hg^II salts is reported. X- Ray structural studies have been carried out on [CoLX₂](X = Cl or Br), [RhLCl₂]PF₆, and [CuLCl₂]·0.5C₇H₈. These structures are compared with those found earlier for [AgL(O₂CMe)]·2H₂O, [PdL][PF₆]₂, and [PdL]Cl₂·2H₂O. In all of them the metal ions bond with the macrocyclic ligand atoms in a square-planar, or near square-planar, array and no example of tetrahedral or ‘folded’ coordination geometry was obtained. In these structures, the macrocycle displays four of the five possible relative configurations for the NH hydrogens and sulphur lone pairs. The chelate rings vary from chairs to flattened chairs and twist-boats. Proton and ¹³C n.m.r., u.v.–visible, and conductivity properties of these complexes are also summarised. In solution, facile conversion between two or more configurational isomers occurs for Co^II, Rh^III, Pt^II, and Cd^II complexes, although these are slow on the n.m.r. time-scale. Exchange processes are even faster for Cu^I, Ag^I, Zn^II, and Hg^II complexes although these exist as essentially one configurational isomer. Conformational rigidity of the chelate rings does not appear to complicate the ¹H and ¹³C n.m.r. spectra for any of these complexes.