A trimetal chain cocooned by two heptadentate polypyridylamide ligands.

Compounds of nickel in which a chain of three metal atoms is closely embraced by two interlocking heptadentate dianions derived from a chain of five pyridyl groups linked at the 2, or 2 and 6, positions by four amide nitrogen atoms are reported. This new type of extended metal atom chain (EMAC) compound differs from earlier ones in that ligand exchange at the axial positions cannot occur, because the axial ligands are part of the entire ligand. Four such compounds, all crystallographically characterized, are reported. This work is a proof-of-concept project that will be extended to other metals with these and other homologous ligands.