Convenient access to the tricyanoborate dianion B(CN)₃²⁻ and selected reactions as a boron-centred nucleophile

Abstract

Alkali metal tricyanoborates M2B(CN)3 (M = Na, K) are accessible by the reaction of tricyanofluoroborates with alkali metals (i) in liquid NH3 or (ii) in THF-naphthalene. The M2B(CN)3 are versatile starting materials for the synthesis of K[RB(CN)3] (R = Et, C6F5, CH2=CHCH2).

Cyanohydridoborate Anions: Synthesis, Salts, and Low‐Viscosity Ionic Liquids

“…The syntheses of salts of 2 and 3 known, so far, are summarized in Scheme . In 1983 the first syntheses for salts of both anions were reported . Na 3 ⋅2 dioxane was obtained starting from Na[BH 4 ] and Hg(CN) 2 .…”

“…Follow‐up metathesis with organic chlorides or bromides gave organic salts and ILs with anion 2 . Instead of tetracyanoborates, easily accessible tricyanofluoroborates M [BF(CN) 3 ] ( M =Na, K) can be used to synthesize M 2 B(CN) 3 . M [BF(CN) 3 ] and M [BF 2 (CN) 2 ] were reduced in ethanol to yield salts of 2 and 3 in a single step…”

“…[15,16] In 1983 the first syntheses for salts of both anions were reported. [10,12,[15][16][17][18][19][20][21][22] Na3·2 dioxanew as obtained startingfrom Na[BH 4 ]a nd Hg(CN) 2 . [16] Because of the byproducts mercury and HCN, this method is not applicable for the preparation of larger quantities of dicyanodihydridoborates.…”

Easy access to nucleophilic boron through diborane to magnesium boryl metathesis

“…Although a rich and varied chemistry has since arisen from the reactivity of compound 1 and related N- heterocyclic boryl anions with organic914, transition metal15161718 and main group electrophiles1419202122232425, alternative nucleophilic boron reagents remain very rare species262728293031. Notable exceptions are Braunschweig's dimetalloborylene and borolyl anions (for example, 2 and 3 )3233 Bertrand and Kinjo's carbene-stabilised monovalent boron species (for example, 4 )3435363738 and a remarkable tricyanoborandiyl dianion394041. Although the transient generation of {BH 2 } − anion equivalents has also been achieved within the coordination sphere of 1,3-bis-(2,6-diisopropyl-phenyl)imidazol-2-ylidene42, the syntheses of all these species require strongly reducing and potentially problematic reaction conditions (for example, Li metal or C 8 K) to achieve the formal B(I) oxidation state.…”

Low Melting Tetracyanidoborate Salts with Alkyl‐, Arylammonium, and Pyridinium Cations: Syntheses, Structures, Properties.

“…This range indicates that the electron density at the B atom in the TCB anion is very high resulting in a weak coordination ability at the N atoms. It increases on replacement of the CN groups by other ligands . Because of this weak coordination property TCB salts with organic cations tend to be ionic liquids.…”