Structural diversity and spectral and thermal properties of the first alkaline earth metal tetracyanidoborates: [Mg(H₂O)₆][B(CN)₄]₂, [Mg(H₂O)₂][B(CN)₄]₂, [Mg(DMF)₆][B(CN)₄]₂, [Ca(H₂O)₃][B(CN)₄]₂, and [Ca(H₂O)₂(CH₃CN)][B(CN)₄]₂

Abstract

The first members of tetracyanidoborate salts with alkaline earth cations, [Mg(H2O)6][B(CN)4]2 (1), [Mg(H2O)2][B(CN)4]2 (2), [Mg(DMF)6][B(CN)4]2 (3), [Ca(H2O)3][B(CN)4]2 (4), and [Ca(H2O)2(CH3CN)][B(CN)4]2 (5), were synthesized. Their structures, obtained by single crystal X-ray diffraction, IR- and Raman spectra, as well as their thermal properties were determined. Whereas 1 and 3 consist of isolated ions, the other three compounds comprise coordination polymers. IR and Raman spectra give information about the coordination modes of the respective tetracyanidoborate anions. Calorimetric measurements show that the coordinated solvent molecules can be removed at elevated temperatures and anhydrous/solvent free compounds form. The anhydrous compounds are thermally very stable. They do not start to decompose below 500 °C. No melting is observed below decomposition.

Cyanoborates

“…Examples are Ag[B(CN) 4 ],[12a] M [B(CN) 4 ] 2 ( M = Cu, Zn, Hg), complex transition metals salts, e.g. with iron and cobalt, alkaline earth metal salts, and rare‐earth metal salts . Not only metatheses starting from alkali metal tetracyanoborates, but also TCB ‐ILs, e.g.…”

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

“…[5,7,22,23] This is obvious from a comparison of their stability against the oxonium ion; (H 3 O)[B(CN) 4 ] [18,19] and (H 3 O)[BF(CN) 3 ] [18,20] are stable in the solid and in solution, whereas (H 3 O)[BF 2 (CN) 2 ] is stable in solution, only, [18] and (H 3 O)[BF 3 (CN)] decomposes even in aqueous solution. Examples for coordination compounds with the TCB and MFB ion include main group metal salts [24] and transition metal [8,25,26,27] as well as lanthanide complexes. [15,28] Again, potential applications have been studied, for example, Li[BF(CN) 3 ] was tested as component of non-aqueous electrolytes used in lithium batteries.…”

Rare‐Earth Tetracyanidoborate Salts – Structural Features and Properties Including Luminescence of [RE­(H2O)8][B(CN)4]3·nH2O and [RE­(H2O)7{κ1N‐B(CN)4}][B(CN)4]2 (RE = Y, Tb, Dy, Ho, Er, Tm, Yb, Lu; n ≤ 3)

“…Even though the anion has a weak coordination ability, network structures are observed quite often with strong Lewis acidic mono-or divalent metal cations. [7][8][9][10][11][12][13][14][15][16][17] To date, only one tetracyanidoborate salt has been described with a triply charged metal cation, namely, [Fe(H 2 O) 6 ][B(CN) 4 ] 3 . [1] Tetracyanidoborate salts have been tested for many useful applications, for example, for use in ionic liquids, membranes, fuel cells, or as battery electrolytes.…”