1-Sila-[1]ferrocenophanes, structure and reactivity: Ring-opening by reactions with boron halides

1-Sila-[1]ferrocenophanes (1–5) were studied with respect to their NMR spectroscopic parameters, in particular the coupling constants involving the carbon atom C(1) [1J(13C(1),13C(2,5)), 1J(29Si,13C(1)) and 1J(57Fe,13C)]. The disiloxane 6, containing two 1-sila-[1]ferrocenophane units, possesses a linear SiOSi group, as shown by X-ray structural analysis, being different from the bent structure of the same compound that has been reported in the literature. Ring-opening reactions of the complexes 2–5 with some boron halides (PhBCl2, BCl3, BBr3 and BI3) gave the ferrocene derivatives 7–12, in which the cyclopentadienyl rings bear silyl and boryl groups, respectively. Two of these complexes (9a and 10) were treated with lithium diethylamide in a 1:1 molar ratio, and in both cases selective substitution at the boron atom was observed (13, 14). All products were characterised by their 1H-, 11B-, 13C- and 29Si-NMR data.