The Role of [BF₄]⁻ and [B(CN)₄]⁻ Anions in the Ionothermal Synthesis of Chalcogenidometalates

Abstract

The role of borate anions in ionothermal syntheses of crystalline chalcogenidometalates was shown by the directed ionothermal synthesis of seven new selenidostannates in ionic liquids with either [BF ] or [B(CN) ] anions. Single crystal structures are presented of four compounds, (C C C Im) [Sn Se ][BF ] (1, Im=imidazolium), (DMMPH) [Sn Se ] (2, DMMP=2,6-dimethylmorpholine), (C C Im) (DMMPH) [Sn Se ] (3), and K [Sn Se ] (4), and how the chosen ionic liquid anion, and the reaction temperature, influences the product spectrum is discussed: Notably, 1 contains an entire formula unit of the ionic liquid, (C C C Im)[BF ], while 4 contains neither the cation nor the anion of the ionic liquid-both observations being very uncommon for ionothermal syntheses. Three further compounds were obtained that exhibit strong disorder in the crystal structures (I-III), for which only their anionic substructures are discussed herein. Compound 4 and I-III are based on the same layered selenidostannate substructure, 2D-{[Sn Se ] }, yet with different inter-layer distances, which is clearly reflected in the crystal colors and quantitative optical absorption properties.

Cyanoborates

“…[EMIm][B(CN) 4 ], can be used for the preparation of metal salts via ionothermal reactions, for instance for the preparation of lanthanum tetracyanoborate coordination polymers. [44c] Recently, related ionothermal reactions of EMIm‐ TCB to give chalcogenidometalates were published …”

Ionic liquid cations as methylation agent for extremely weak chalcogenido metalate nucleophiles

“…Besides the well-known incorporation of ionic liquid cations as a whole,15–21 methylation of amines22 was observed upon their addition as auxiliary agents for controlling the basicity of the reaction medium or as structure-directing agents 23. Recently, we have furthermore reported the distinct influence of the ionic liquid anion on the course of the reactions, though the incorporation of the anions in the finally isolated reaction products has remained rare so far 24…”

Innovative Syntheses of Cyano(fluoro)borates: Catalytic Cyanation, Electrochemical and Electrophilic Fluorination

“…[12,13] These cyanoborate-ILs have been used as reaction media for ionothermal synthesis providing access to new compounds that often contain cyanoborate anions as an integral component. [14,15] The aforementioned beneficial properties of cyanoborate-ILs are related to the stabilizing effect of the cyano group due to its electron withdrawing nature. [6] Furthermore, in recent years other cyanoborate-ILs were developed, [6] which include ILs with cyanohydridoborate anions [BH n (CN) 4Àn ] À (n = 1-3) [16] and perfluoroalkylcyano(fluoro)borate anions [R F BF n (CN) 3Àn ] À (n = 0-2).…”