Ligands containing alternating 2,6-linked pyridine and 2,5-linked thiophene units

A variety of linear assemblies of alternating pyridine (2,6-linked) [P] and thiophene (2,5-linked) [T] units have been generated with up to seven units and their macrocyclisation investigated The optimal methods involved the palladium(0) catalysed reaction of thienyl Grignard reagents with bromopyridines. In this way were made TPT, TPTPT, TPTPTPT, BrPTPBr and various XCH2PTPTPCH2X derivatives (X = H, Br, OH, OR and SBu-t). Alternative routes whereby pyridine units were 2,6-linked by CH2SCH2 units, with the intention of converting the bridge groups into thiophenes by a Hinsberg reaction, were-also studied. The latter products. {(HOCH2[P]CH2)(2)S and (HOCH2[P]CH2SCH2)(2)[P]} proved to be highly effective ligands for transition metals, especially divalent ones such as Co2+, Ni2+ and Zn2+. No macrocyclisations were effective.