PYRIDYL-FUNCTIONALIZED CYCLOPENTADIENYL LIGANDS - BUILDING-BLOCKS FOROLIGONUCLEAR ORGANOMETALLIC ASSEMBLIES

Lithiated 2-methylpyridine reacts with 2,3,4,5-tetramethylfulvene (TMF ) to give 2-[2-(2,3,4,5-tetramethylcyclopenta-1,4-dien-1-yl) ethyl]pyr idine (2H) after aqueous work-up. Similarly, a mixture of tetramethylc yclopenta-1,4-dien-1-yl)ethyl]pyridine (3H) and tetramethylcyclopenta- 1,4-dien-1-yl)ethyl]pyridine (4H(2)) was obtained from monolithiated 2 ,6-dimethylpyridine and TMF. All three compounds were obtained as a ro ughly statistical mixture of double-bond isomers. 2-Lithiopyridine rea cts with 2,3,4,5-tetramethylcyclopent-2-enone to yield 3,4,5-tetrameth ylcyclopenta-1,3-dien-1-yl)pyridine (5H) after acidic work-up. This co mpound was obtained as a nonstatistical mixture of double-bond isomers , which is presumably due to intramolecular hydrogen-bond interactions . The Lithiated derivatives 2Li, 3Li and 5Li react with iron(II) chlor ide to afford the respective ferrocenes (2)(2)Fe (8), (3)(2)Fe (9) and (5)(2)Fe (10). The structure of 10 was determined by a single-crystal X-ray diffraction study. The cyclopentadienyl ii gands adopt a stagge red conformation; the pyridyl rings are arranged in a stacked fashion with the closest ring-ring contact being 3.16 Angstrom. The distance b etween the iron atom and the cyclopentadienyl ring centroids is 1.66 A ngstrom.