Journal Article

Isolation and electronic structures of derivatized manganocene, ferrocene and cobaltocene anions

Evans, Peter, Hill, Stephen, Goodwin Conrad A P, Vonci Michele, Nicholas, Hannah M, Greer, Samuel M, Mills, David P, Giansiracusa, Marcus J, Chilton, Nicholas F

2021

Overview

The discovery of ferrocene nearly 70 years ago marked the genesis of metallocene chemistry. Although the ferrocenium cation was discovered soon afterwards, a derivatized ferrocenium dication was only isolated in 2016 and the monoanion of ferrocene has only been observed in low-temperature electrochemical studies. Here we report the isolation of a derivatized ferrocene anion in the solid state as part of an isostructural family of 3d metallocenates, which consist of anionic complexes of a metal centre (manganese, iron or cobalt) sandwiched between two bulky Cpttt ligands (where Cpttt is {1,2,4-C5H2tBu3}). These thermally and air-sensitive complexes decompose rapidly above −30 °C; however, we were able to characterize all metallocenates by a wide range of physical techniques and ab initio calculations. These data have allowed us to map the electronic structures of this metallocenate family, including an unexpected high-spin S = 3/2 ground state for the 19e− derivatized ferrocene anion.Unlike ferrocene and its cationic counterpart ferrocenium, the ferrocene monoanion is an unusual species that has been observed through low-temperature electrochemical studies. Now, a family of isostructural 3d metallocenates has been isolated that consists of a manganocene, a cobaltocene and a high-spin ferrocene anion stabilized by cyclopentadienyl ligands bearing bulky aliphatic groups.

• Publisher: Nature Publishing Group
• Subject: Anions / Cations / Cobalt / Coordination compounds / Electrochemistry / Ligands / Low temperature / Manganese