Conjugated Pyridines with an End-Capping Ferrocene

This study reports the synthesis of new pyridyl ligands incorporating an alkyne entity with an end-capping ferrocenyl moiety: 1-(ferrocenylethynyl)-4-((4-pyridyl)ethynyl)benzene (FEPEB), 1-ferrocenyl-6-(4-pyridyl)hexatriyne (FPHT), and 1-ferrocenyl-4-(4-pyridyl)butadiyne (FPBD). The complexes W(CO) 4 (L)(FEPEB) (L = CO, PPh 3, P(OMe) 3, PMe 3 ), W(CO) 4 (L)(FPHT) (L = CO, PPh 3, P(OMe) 3, PMe 3 ), and W(CO) 5 (FPBD) are obtained by ligating FEPEB, FPHT, and FPBD to W(CO) 4 (L)(THF). The energy of tungsten metal to pyridyl π* charge transfer (MLCT) depends on both the pyridyl ligand and the ancillary ligand, L. Treating FPHT and FPBD with MeI causes N -methylpyridinium derivatives to form, which exhibit a strong low-lying charge-transfer band. As a comparative study, the complexes 1-(ferrocenylethynyl)-4-((4-nitrophenyl)ethynyl)-benzene (FENEB) and 1-(ferrocenylethynyl)-4-((4-aminophenyl)ethynyl)benzene (FEAEB) have also been synthesized. X-ray analysis has been employed to examine the structures of 1-(ferrocenylethynyl)-4-ethynylbenzene, W(CO) 4 (PPh 3 )(FEPEB), W(CO) 5 (FPHT), and 1,8-diferrocenyloctatetrayne.