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

Abstract

[Structure: see text]. 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 x 10(4).

Ferrocene‐Based Trimethylsilyl Chalcogenide Reagents for the Assembly of Functionalized Metal–Chalcogen Architectures

“…However, the solid-state structures of 12 and 13 are actually most closely related to the one-directional [Cd(TeC 6 H 2 Me 3 ) 2 ] 1 and [Ag 10 10 ] 1 complexes. [21] Although the coordination polymers 12 and 13 do not contain any phosphine ligands, the structures can be described in a manner similar to that of 20c] with the shortest bond length to the linear silver center.…”

“…Ferrocenoyl chloride was first prepared in situ through the addition of oxalyl chloride to a stirred suspension of ferrocene carboxylic acid in CH 2 Cl 2 at RT. [10] The reaction with NEt 3 / 2-bromoethanol generated 2-bromoethylferrocenylcarboxy- [7g] However, the chalcogenols [FcC(O)OCH 2 CH 2 EH] (2a E = S, 3a E = Se) could be prepared through the addition of tetrabutylammonium fluoride hydrate (TBAF) to a wellstirred solution of 1 with EA C H T U N G T R E N N U N G (SiMe 3 ) 2 in THF at À10 8C. [11] Tetrabutylammonium bromide was removed through precipitation with heptane and filtration of the reaction mixtures.…”

“…À (E = S, Se), [31] [FcC(O)OH], [32] [FcC(O)Cl], [10] were prepared and purified according to literature preparations. Celite was dried by heating at 100 8C under vacuum for 48 h. AgOAc was purchased from Strem Chemicals.…”

First preparation and isolation of a stable ferrocenylketene

“…3 1,2-Bisferrocenyl-1,2-bisketene 4 was also prepared as a transient intermediate by photochemical ring opening of the corresponding cyclobutenedione 3, and 4 underwent rapid ring closure back to the cyclobutenedione with a rate constant 67 times greater than that for the corresponding 1,2-diphenyl-1,2-bisketene (Scheme 2). 3 Thus the computational and experimental results indicated that ferrocenylketenes are less stabilized and more reactive than phenylketenes. This is consistent with the known destabilizing effects of electron donating substituents on ketenes, 1d and the strong electron donating ability of the ferrocenyl group.…”

“…Ferrocenylketene 1 was generated by Wolff rearrangement in CH 3 CN and was directly observed by UV and IR spectroscopy as a short-lived and reactive intermediate in solution. 3 Ferrocenylketene was identified by the characteristic IR band at 2119 cm -1 , and was found to have a rate constant for reaction with n-BuNH 2 forming the corresponding amide less than that for phenylketene by a factor of 5 (Scheme 2). 3 1,2-Bisferrocenyl-1,2-bisketene 4 was also prepared as a transient intermediate by photochemical ring opening of the corresponding cyclobutenedione 3, and 4 underwent rapid ring closure back to the cyclobutenedione with a rate constant 67 times greater than that for the corresponding 1,2-diphenyl-1,2-bisketene (Scheme 2).…”