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1.3 V Inorganic Sequential Redox Chain with an All-Anionic Couple 1–/2– in a Single Framework

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journal contribution
posted on 24.10.2021, 14:13 by Ana B. Buades, Clara Viñas, Xavier Fontrodona, Francesc Teixidor
The relatively low symmetry of [3,3′-Co­(1,2-C2B9H11)2] ([1]), along with the high number of available substitution sites, 18 on the boron atoms and 4 on the carbon atoms, allows a fairly regioselective and stepwise chlorination of the platform and therefore a very controlled tuning of the electrochemical potential tuning. This is not so easily found in other systems, e.g., ferrocene. In this work, we show how a single platform with boron and carbon in the ligand, and only cobalt can produce a tuning of potentials in a stepwise manner in the 1.3 V range. The platform used is made of two icosahedra sharing one vertex. The E1/2 tuning has been achieved from [1] by sequential chlorination, which has given potentials whose values increase sequentially and linearly with the number of chloro groups in the platform. [Cl8-1], [Cl10-1], and [Cl12-1] have been obtained, which are added to the existing [Cl-1], [Cl2-1], [Cl4-1], and [Cl6-1] described earlier to give the 1.3 V range. It is envisaged to extend this range also sequentially by changing the metal from cobalt to iron. The last successful synthesis of the highest chlorinated derivatives of cobaltabis­(dicarbollide) dates back to 1982, and since then, no more advances have occurred toward more substituted metallacarborane chlorinated compounds. [Cl8-1], [Cl10-1], and [Cl12-1] are made with an easy and fast method. The key point of the reaction is the use of the protonated form of [Co­(C2B9H11)2], as a starting material, and the use of sulfuryl chloride, a less hazardous and easier to use chlorinating agent. In addition, we present a complete, spectroscopic, crystallographic, and electrochemical characterization, together with a study of the influence of the chlorination position in the electrochemical properties.