Binucleating N6 24- and 26-membered macrocyclic ligands. Part 1. Dilead complexes: X-ray crystal structure determination of a macrocyclic dilead complex containing nitrogen-only bridging thiocyanate

Abstract

The relatively restricting macrocycle 8,14,22,28-tetramethyl-9,13;23,27-dinitrilo-1,7,15,21 -tetra-aza-cyclo-octacosa-7,9,11,14,21,23,25,28-octaene ( L¹) co-ordinates to two lead atoms in such a way that the preferred bonding mode for bridging thiocyanate is a single-atom N only bridge. Infrared absorption in the range 1 950–1 970 cm^–1 is observed with mono-, bis-, and tetra-thiocyanato dilead complexes of this ligand. X-Ray structural analysis has been carried out on the tetrathiocyanato complex Pb₂L¹(NCS)₄ and confirms the N only bridge, the first example of a [graphic omitted]CS linkage. Spectroscopic evidence suggests that dilead thiocyanato complexes of a larger similar macrocycle (containing two more methylenes) may have a weakly bonded N only bridge, which is not retained on anion exchange. These macrocycles seem likely to generate binuclear transition metal complexes with interesting properties.