Preparation and some chemistry of ferrocenylethynyl ketones

Abstract

Reactions of Fc′(CHO)2 1 (Fc′ = 1,1′-ferrocenediyl) with LiCCR gave substituted propargylic alcohols Fc′{CH(OH)CCR}2 (R = SiMe3 2, Fc 9). Oxidation (MnO2) of these alcohols afforded the bis(alkynyl ketone)s Fc′{C(O)CCR}2 (R = SiMe3 3, Fc 10), the former being accompanied by the partially desilylated Fc′{C(O)CCH}-1-{C(O)CCSiMe3}-1′ 4. The reaction between 4 and RuCl(dppe)Cp in the presence of Na[BPh4] gave the cyclic vinylidene complex [Ru{CC[C(O)Fc′C(O)CHCH]}(dppe)Cp]BPh4 5. The diastereomers were separated by flash chromatography (2) or preparative t.l.c. (9) to give the cis (2a, 9a) and trans (2b, 9b) isomers. Cyclisation of each isomer to the corresponding ferrocenophane was catalysed by pTSA to give Fc′{[CH(CCR)]2O} (R = SiMe3 6a, 6b; Fc 11a, 11b), of which 6a, 6b could be desilylated to Fc′{[CH(CCH)]2O} 7a, 7b, and further transformed into the bis(η2-alkyne-dicobalt) complexes Fc′{[CH(η2-C2H[Co2(μ-dppm)(CO)4])]2O} 8a, 8b with Co2(μ-dppm)(CO)6. Molecular structures of 3, 5, 6a, 6b, 7a, 7b and 10 were determined by single-crystal XRD methods.