Isolation and crystal and molecular structures of [(CHBr)Fe], [(CHBr)Fe] and [(CBr)(CBrHgBr)Fe].

The reaction of [(CHBr)Fe] with lithium tetramethylpiperidinide (LiTMP) in a 1:10 molar ratio in tetrahydrofuran yields, after quenching with CHBr, a mixture of the polybromoferrocenes [CHBrFe] with n = 4-9, from which single crystals of bis(1,2,3-tribromocyclopentadienyl)iron(II), [Fe(CHBr)], and bis(1,2,3,4-tetrabromocyclopentadienyl)iron(II), [Fe(CHBr)Fe], were obtained by a combination of chromatography and fractional crystallization. Treatment of `[C(HgOAc)Fe]' with KBr yields a mixture of polybromoferrocenes [CHBrFe] with n = 8-10 and bromomercurioferrocenes [CHBr(HgBr)Fe] with n = 7-9, from which single crystals of (1-bromomercurio-2,3,4,5-tetrabromocyclopentadienyl)(1,2,3,4,5-pentabromocyclopentadienyl)iron(II), [FeHgBr(CBr)(CBr)], were obtained by fractional crystallization. The crystal structures of all the compounds show Br...Br, Br...H and sometimes Br...Cp...π (Cp is a ring centroid) interactions, as well as π-π interactions. The findings are supported by Hirshfeld analyses.