Ferrocenylketene and Ferrocenyl-1,2-bisketenes: Direct Observation and Reactivity Measurements

Ferrocenylketene (1) is calculated to be destabilized by 1.6 kcal/mol relative to phenylketene (10)
by B3LYP isodesmic comparison to the corresponding alkenes. Ketene 1 generated by Wolff
rearrangement in CH3CN is identified by the IR band at 2119 cm-1 and has a rate constant for
reaction with n-BuNH2 less than that for 10 by a factor of 5. 1,2-Bisferrocenyl-1,2-bisketene 18
and 1-ferrocenyl-2-trimethylsilyl-1,2-bisketene 21 were prepared by photochemical ring opening
of the corresponding cyclobutenediones, and 18 undergoes rapid ring closure 67 times faster than
the corresponding 1,2-diphenyl-1,2-bisketene, while bisketene 21 is longer lived than 18 by a factor
of 3.2 × 104.