2-Pyridylmetallocenes: Part 3 [1]. Cyclomercuration of 2-pyridyl-ferrocene and 1-(2-pyridyl)-2-methyl-ferrocene. Molecular structures of [1-(2-C5H4N)-2-(CH3)C5H3]Fe(C5H5), [1-(ClHg)-2-(2-C5H4N)C5H3]Fe(C5H5) and [1-(ClHg)-2-(2-C5H4N)-3-(CH3)C5H2]Fe(C5H5)

Mercuration of 2-pyridylferrocene [(2-C5H4N)C5H4]Fe(C5H5) (1a) and its 2-methylated derivative 1b with Hg(OAc)2 followed by treatment with LiCl gave after chromatographic workup the cyclomercurated and [1-(ClHg)-2-(2-C5H4N)-3-(R)C5H2]Fe(C5H5) (R = H: 2a; Me: 2b)) in 43% and 21% yield. The molecular structures of 1b, 2a and 2b have been determined by X-ray crystallography.

The 2-pyridyl metallocenes [(2-C5H4N)(R)C5H3]Fe(C5H5) (R = H, Me) can be mercurated by Hg(OAc)2/LiCl to give the corresponding cyclomercurated compounds [1-(ClHg)-2(2-C5H4N)(3-R)C5H2]Fe(C5H5) in moderate yields. The crystal structure determinations show weak N–Hg interactions, however with no deviation from linearity of the C–Hg–Cl bond. Also the formation of intermolecular contacts between two HgCl groups on one side and weak hydrogen bonds between one chloride and a cyclopentadienyl proton of a neighboring molecule lead to a polymeric structure.Figure optionsDownload as PowerPoint slideHighlights
► Pyridylferrocenes and Hg(OAc)2/LiCl react to give [(ClHg)(2-C5H4N)C5H2R]Fe(C5H5).
► X-ray structure determination shows weak Hg coordination of the pyridine nitrogen.
► Intermolecular Hg2Cl2 contacts and CH–Cl hydrogen bonds lead to polymeric structure.