Z/E isomerisation of ferrocenyl- and arylmethylidene-substituted derivatives of quinuclidine and camphor

2-Ferrocenylmethylidene-3-methyl-1-azoniabicyclo[2,2,2]octane-3-cation and 2-ferrocenylmethylidene-1,2,7,7-tetramethylbicyclo-[2,2,1]heptane-2-cation tetrafluoroborates and tetraphenylborates having bulky substituents in their molecules have been found to isomerise in solutions with inversion of configuration at the double bond. Tetrafluoroborates and tetraphenylborates of the 3-methyl-2,3-(1-piperidinium-1,4-diyl)-1-ferrocenylallyl cation and the 3-methyl-2,3-(1,2,2-trimethylcyclopentane-1,3-diyl)-1-ferrocenylallyl cation with bulky substituents at the C₁ atom isomerise in solutions with inversion of configuration at the C₁–C₂ bond.