Formation of a strained [3]ferrocenophane via base-catalyzed intramolecular cyclization

Carbon-Rich Trinuclear Octamethylferrocenophanes

“…A similar reaction has been reported when 1,1′-bis-(ferrocenoyl)ferrocene was treated with a large excess of both MeLi and AlCl 3 (6b, Scheme 2). 53 In that case, the isolation of a 1,1′-divinyl species was not reported, and a mechanism involving nucleophilic addition of a methyl group and subsequent deprotonation followed by rearrangement was proposed. In light of the results presented here, it seems likely that 1,1′-bis(1-ferrocenylvinyl)ferrocene is intermediate in the formation of 6b.…”

“…As expected, none of the terminal ferrocenes exhibit a noteworthy tilt. The central ferrocene of 6b is reported to have a tilt angle of 8.5° . The slightly smaller tilt regarding of 6 and the essentially non-tilted structures of 5 and 7 are in line with our previous observation that octamethylferrocenophanes are less tilted compared to non-methylated ferrocenophanes of similar structure, likely due to steric repulsion between the methyl groups on opposing rings.…”

Intramolecular Hydroalkylation as a Route to Strained Dicationic Bis(arene) [3]Ruthenocyclophanes

“…Previously reported propenyl-bridged [3]metallocenophanes possess structural features (α ≈ 10−14°, large internal bond angles in the bridge) very similar to those observed for 4 [BPh 4 ] 2 . − However, the lack of consensus as to how much ring strain is present in these complexes produces descriptions varying from essentially unstrained 38 to dramatically strained . The presence of significant ring strain in 3 and 4 can be independently demonstrated by the fact that the arene ligands in these complexes are more susceptible to dissociation than in unbridged bis(arene)ruthenium complexes.…”

1,1′-(1-Propene-1,3-diyl)-ferrocene: modified synthesis, crystal structure, and polymerisation behaviour

“…The most prominent feature of the structure, which should be relatively unaffected by the disorder is the ring tilt of 11.3°. This angle is somewhat larger than those observed for other [3](1,1 0 )ferrocenophanes with saturated bridges (8.8-10.9°) [32][33][34][35][36]; comparable dehydro [3](1,1 0 )ferrocenophanes, 1,1 0 -(1-ferrocenyl-1-propene-1,3-diyl)-ferrocene and 1,1 0 -(1,3-diferrocenyl-3-methyl-1-propene-1,3-diyl)-ferrocene, have ring tilts of 12.3°and 12.6°, respectively [39,37,38]. Ring tilts of 7.2°and 11.1°have been reported for two independent molecules of the unsaturated [4]ferrocenophane, 1,1 0 -(1-methoxybutadiene-1,4-diyl)-ferrocene [40]; values of 21.6°and 23°have been reported for CH 2 CH 2 and CH@CH bridged [2]ferrocenophanes, respectively [4,11].…”