The Reduction Chemistry of Ferrocenylborole

Abstract

Time to B radical: One‐electron reduction of 1‐ferrocenyl‐2,3,4,5‐tetraphenylborole results in a radical anion with 5 π electrons in the borole ring. Both EPR spectroscopic investigations and spin density calculations confirm the formation of a borol radical (see picture). Further reduction stimulates an intramolecular [(C5H5)Fe] migration from the cyclopentadienyl anion to the borole dianion.

A theoretical study of the aromaticity in neutral and anionic borole compounds

“…In addition, we have investigated corresponding NICS values for the negatively charged derivatives. As previously reported by the groups of Herberich, [52] Yamaguchi [18] and Braunschweig, [15,17,[53][54][55] the synthesis and isolation of various dianionic and a monoanionic species has been successfully achieved ( Figure 4). The addition of one electron noticeably decreases the antiaromatic character of boroles, as judged by both the NICS and multicenter indices.…”

A Computational Study on a Strategy for Isolating a Stable Cyclopentadienyl Cation

“…[14] Piers and co-workers reported the perfluorinated analogue (5) shortly thereafter. [15] These compounds are indefinitely stable when stored under N 2 or Ar and both species have demonstrated unusual and interesting reactivity, such as H 2 activation, [16][17] reduction chemistry, [18][19][20][21][22] and CO ligation. [23] The boroles owe their increased stability (although they are very strong Lewis acids) to a loss in degeneracy in the highest occupied molecular orbital (HOMO) from [Cp] + , which is caused by the smaller electronegativity of boron in comparison with carbon in [Cp] + (Figure 1).…”

O,N,B-Containing eight-membered heterocycles by ring expansion of boroles with nitrones

“…As the O1−B1 bond (1.360 (2) As mentioned above, we observed an initial deep red colour of the reaction solutions below −50 °C. Given that both boroles and nitrones are known to form stable radicals, 34,43,44,45 we also considered a radical reaction mechanism in which a borole monoradical anion and/or a nitrosyl radical might be involved. To this end, EPR measurements at 180 -200 K were carried out during the reaction of borole 2 and nitrone 3, as this reaction seems to produce the most stable intermediate.…”