A new NS4 quinquedentate macrocyclic ligand: synthesis, structure and properties of its Ni(ii), Pd(ii), Pt(ii), Cu(ii), Cu(i) and Ag(i) complexes

Abstract

An aza-thia macrocycle 2,5,14,17-tetrathia[6](1,2)benzeno[6](2,6)pyridinophane (11) and its complexes with Ni(II), Pd(II), Pt(II), Cu(II), Cu(I) and Ag(I) were synthesized and their crystal structures were determined. Ni(II) forms an octahedral complex coordinated to NS₃ of the ligand and two chlorine atoms of the metal salt; one of the sulfurs in the ligand is uncoordinated. The crystal structures of [Pd·11][PF₆]₂ and [Pt·11][PF₆]₂ confirm a [NS₃ + S] coordination in both complexes. NMR spectroscopic studies indicate that only one form of each complex is present in solution. Cu(II), Cu(I) and Ag(I) complexes of the macrocycle adopt a geometry in between a square pyramid and a trigonal bipyramid with NS₄ coordination around the metal ions in [Cu·11][ClO₄]₂, [Cu·11][PF₆] and [Ag·11][PF₆]. The electronic and redox properties of [Pd·11][PF₆]₂, [Pt·11][PF₆]₂ and the copper complexes in acetonitrile have been examined. The complexation behaviour of the macrocycle, 11, has also been studied in solution and found to lack good selectivity towards the selected transition metal ions.