Copper(II) template synthesis of a new N ₂S ₂-donor macrocycle incorporating a pendent pyridyl substituent

The synthesis of the new potentially pentadentate ligand, 2,2′-(2-methyl-2-(pyridin-2-yl)propane-1,3-diyl)bis(sulfanediyl) diethanamine (L ¹ ), containing two thioether sulfurs, two -NH ₂ amines and a pyridyl nitrogen heteroatom is described. Reaction of L ¹ with copper(II) chloride and addition of hexafluorophosphate anion has led to isolation of the mixed anion complex Cu ₂(L ¹ ) ₂Cl(PF ₆) ₃. The synthesis and X-ray structure of cobalt(III) species, [Co(L ¹ )Cl](PF ₆) ₂, is also reported. In situ reaction of L ¹ with copper(II) as a metal template in the presence of formaldehyde and the carbon acid nitroethane together with triethylamine (as base) led to macrocycle ring closure to yield [Cu(L ² )Cl]PF ₆ (where L ² = 6,13-dimethyl-6-nitro-13-(pyridin-2-yl)-1,11-dithia-4,8- diazacyclotetradecane) whose X-ray structure shows that the copper centre has a distorted square pyramidal coordination geometry being bound by both -NH ₂ nitrogens and both sulfurs of L ² while the pyridyl nitrogen remains uncoordinated.