Systematic Approach to the Synthesis of Cobaltocenium Salts with Reduced Forms of TCNQF 4 : Two [Cp 2 Co](TCNQF 4 ) Polymorphs and [Cp 2 Co]Li(TCNQF 4 )
journal contribution
posted on 2024-11-02, 20:18authored byJinzhen Lu, Ruchika OjhaRuchika Ojha, Alan Bond, Lisandra Martin
Three new crystallographically characterized compounds were prepared in high yield from reactions between [Cp 2 Co]PF 6 (Cp = cyclopentadiene) and lithium salts of the radical anion of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (TCNQF 41- ) or the dianionic TCNQF 42- . The two [Cp 2 Co]TCNQF 4 compounds (1 and 2) with 1:1 stoichiometry were found to be polymorphic, α and β. Remarkably, the syntheses only differed by the presence of a small amount of neutral TCNQF 4 in the case of polymorph β (2). The role of the TCNQF 4 has been rationalized on the basis of a transient intermediate, postulated as [Cp 2 Co](TCNQF 4 ) 2 . Compound 3 contains TCNQF 42- and crystallized as [Cp 2 Co]Li(TCNQF 4 ). This material highlights a novel coordination mode for the Li + cation that participated in the formation of a metal-organic framework accommodating the [Cp 2 Co] + cation. All complexes were comprehensively characterized by Fourier transform infrared spectroscopy, UV-vis spectroscopy, and electrochemistry. Polymorph β (2) has a conductivity of 5.8 × 10 -4 S cm -1 , which lies well within the semiconductor range. Previous work in this area employed redox chemistry based on the reaction of cobaltocene or ferrocene with neutral TCNQ. The introduction of metathesis reactions enhances the synthetic flexibility enabling a systematic approach to new materials.