THE SYNTHESIS OF SOME LIPOPHILIC TETRADENTATE LIGANDS FOR USE IN THE FORMATION OF METAL-LINKED POLYMERS

Two lipophilic tetradentate ligands, 5,5'-di-t-butyl- and 5,5'-dihexyl-2,2'-bipyrimidine, were prepared via either Ullmann or nickel(0)-promoted reactions in low but useful yields. Approaches towards the synthesis of lipophilic ligands based on 2,2'-biimidazole, namely 4,4',5,5'-tetrabutyl-2,2'-biimidazole (from decane-4,5-dione) and various 4,4',5,5'-tetra(arylamino)-2,2'-biimidazoles (from 4,4',5,5'-tetrabromo-2,2'-biimidazole and arylamines), and a 2,2'-bibenzimidazole, 5,5',6,6'-tetra(octyloxy)-2,2'-bibenzimidazole (from NN'-bis[4,5-di(octyloxy)-2-nitrophenyl]oxamide), were uniformly unsuccessful for preparing the 2,2'-biheteroaryl compounds.