[B(CO₂H)₄]⁻ and [B(CNCH₃)₄]³⁺: Homoleptic Boron Complexes Containing Carboxy and Methylisocyanide Ligands

Abstract

Series clincher: The synthesis of salts of the [B(CO2H)4]− ion and the [B(CNCH3)4]3+ ion starting from [nBu4N][B(CN)4] are described. Thus, the series including [B(CN)4]−, [B(CO2H)4]−, and [B(CF3)4]− has now been completed. The figure shows the [B(CO2)2(CO2H)2]3− ion in [Co(NH3)6][B(CO2)2(CO2H)2]⋅2 H2O (O red, C black, B yellow, H white).

Cyanoborates

“…[7e], The [B(CF 3 ) 4 ] – anion is among the most weakly coordinating anions known,[1d], [1e], [7c], [30g], and it was used as starting material for the synthesis of the unprecedented borane carbonyl (CF 3 ) 3 BCO. [7c], [30g], A second example for the transformation of all four CN groups of the TCB anion into other substituents is the permethylation with the strong methylation reagent methyl triflate CF 3 SO 3 CH 3 to give the [B(CNCH 3 ) 4 ] 3+ cation . This cation reacted with water in the presence of HNO 2 to give the tetrakis(carboxylato)borate anion [B{C(O)OH} 4 ] – (Scheme , B ) .…”

“…[7c], [30g], A second example for the transformation of all four CN groups of the TCB anion into other substituents is the permethylation with the strong methylation reagent methyl triflate CF 3 SO 3 CH 3 to give the [B(CNCH 3 ) 4 ] 3+ cation . This cation reacted with water in the presence of HNO 2 to give the tetrakis(carboxylato)borate anion [B{C(O)OH} 4 ] – (Scheme , B ) . The addition of up to four boron‐based Lewis acids to the TCB anion to give [B(CNB R 3 ) 4 ] – ( R = CF 3 (Scheme , C ),[7c], C 6 F 5 , ) is related to the aforementioned permethylation.…”

Syntheses and Structures of New Rare-Earth Metal Tetracyanidoborates

“…[3c], [3f], [3g], [3i], Despite the high stability of the [B(CN) 4 ] – anion in general, tetracyanidoborates have been successfully used as starting materials for the preparation of salts with other borate anions, e.g. [B(CF 3 ) 4 ] – [3e,3f,6] and [B(CO 2 H) 4 ] – . Tetracyanidoborates with large organic cations have low melting points, compose low viscosities, and are classified as room temperature ionic liquids.…”

Biodegradation potential of cyano-based ionic liquid anions in a culture of Cupriavidus spp. and their in vitro enzymatic hydrolysis by nitrile hydratase

“…For example in the case of tetracyanoborate, the borate could already be prepared as a carboxylated anion, e.g. B(CO 2 H) 4 − (Bernhardt et al 2006), and a hydrogenated one, e.g. BH 2 (CN 2 ) (Györi et al 1983), as well as a dianion B(CN) 3 2− (Bernhardt et al 2011) that could change the accessibility of the molecule for enzymatic attack.…”