Ring-opening addition of hydrogen chloride to monocyclic and spirocyclic [1]ferrocenophanes: a convenient and controlled route to ferrocenylchlorosilanes and germanes

Abstract

The ring-opening addition of HCl to [1]ferrocenophanes has been shown to provide a general method for the preparation of chlorosilanes and germanes with ferrocenyl substituents. Reaction of HCl with dimethyl[1]silaferrocenophane, fcSiMe₂ (1a) [fc=Fe(η-C₅H₄)₂], affords chlorodimethylferrocenylsilane, FcMe₂SiCl (3a) [Fc=(η-C₅H₄)Fe(η-C₅H₅)], in 68% yield. Trichloroferrocenylsilane, FcSiCl₃ (3b), and chlorodimethylferrocenylgermane, FcMe₂GeCl (3c), were prepared by an analogous route from ferrocenophanes fcSiCl₂ (1b) and fcGeMe₂ (1c). Ring-opening addition of HCl to the spirocyclic [1]ferrocenophane, fcSi(CH₂)₃ (4), leads to cleavage of the Si–C bond of the strained ferrocenophane, giving the silacyclobutane FcSiCl(CH₂)₃ (5) in 84% yield. Moreover, treatment of the spirocyclic [1]silaferrocenophane fc₂Si (6) with HCl affords orange crystals of dichlorodiferrocenylsilane, Fc₂SiCl₂ (7), in 88% yield. Hydrolysis of 7 in the presence of triethylamine generated diferrocenylsilanediol, Fc₂Si(OH)₂ (8), in 90% yield. A single crystal X-ray diffraction study combined with spectroscopic identification confirmed that 8 crystallizes in a new bead-and-chain motif.