The Hexacyanodiborane(6) Dianion [B₂(CN)₆]²⁻

Abstract

Diborane(6) dianions with substituents that are bonded to boron via carbon are very reactive and therefore only a few examples are known. Diborane(6) derivatives are the simplest catenated boron compounds with an electron-precise B-B σ-bond that are of fundamental interest and of relevance for material applications. The homoleptic hexacyanodiborane(6) dianion [B2 (CN)6 ](2-) that is chemically very robust is reported. The dianion is air-stable and resistant against boiling water and anhydrous hydrogen fluoride. Its salts are thermally highly stable, for example, decomposition of (H3 O)2 [B2 (CN)6 ] starts at 200 °C. The [B2 (CN)6 ](2-) dianion is readily accessible starting from 1) B(CN)3 (2-) and an oxidant, 2) [BF(CN)3 ](-) and a reductant, or 3) by the reaction of B(CN)3 (2-) with [BHal(CN)3 ](-) (Hal=F, Br). The latter reaction was found to proceed via a triply negatively charged transition state according to an SN 2 mechanism.

Lanthanide Coordination Polymers and MOFs based on the Dicyanodihydridoborate Anion

“…The Pr−N (pyridyl) distances of 266.3 and 268.5 pm are also in good agreement with known compounds, for example, the above mentioned 2 ∞ [Pr 2 Cl 6 (μ‐bipy)(py) 6 ] (Pr−N: 263.7–267.3 pm) . Furthermore, the B−C distances are in a range of 157.1(7)–160.5(7) pm and show good accordance with the B−C distances in 3 and the above mentioned literature . Although they exhibit the same coordination number of 8, there are differences in the coordination spheres between 5 and the related compounds 3 ∞ [LnCl 3 {1,3‐C 6 H 4 (CN) 2 }] (Ln=Eu, Tb) as the latter ones show a trigonal prismatic coordination sphere.…”

“…Coordination of cyano groups to lanthanide cations can also be observed when dinitriles such as 1,3‐C 6 H 4 (CN) 2 and 1,4‐C 6 H 4 (CN) 2 are used, leading to the closely related products 3 ∞ [LnCl 3 {1,3‐C 6 H 4 (CN) 2 }] (Ln=Eu, Tb, Ho) and 3 ∞ [LnCl 3 {1,4‐C 6 H 4 (CN) 2 }] (Ln=Sm, Gd, Tb, Y) . Both cyanoborates and dinitriles can be utilized as suitable linkers for lanthanide coordination compounds giving access to new compounds ranging from one‐dimensional up to three‐dimensional coordination polymers . The most evident difference between these ligands is their electronic character, as cyanoborates are anions, acting not only as linker but also assuring charge compensation of the Ln 3+ ions, whereas the neutral dinitriles are donor ligands and require additional components like chloride ions for charge compensation.…”

“…[18] Both cyanoborates andd initriles can be utilized as suitable linkersf or lanthanide coordination compounds giving access to new compounds ranging from one-dimensional up to three-dimensional coordination polymers. [10,[15][16][17][18][19] The most evident differenceb etweent hese ligands is their electronic character,a sc yanoborates are anions, acting not only as linker but also assuring chargec ompensation of the Ln 3 + ions, whereas the neutrald initrilesa re donor ligandsa nd requirea dditional components like chloride ions for chargec ompensation. Despite these differences, both mentioned ligand types can be used to unlock lanthanide luminescence in the obtained products.…”

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.…”

On the Dual Reactivity of a Nucleophilic Dihydrido‐Diborane: Reaction at the B−B Bond and/or the B−H Bond

“…They can be regarded as boryl‐substituted boranes that react as electrophiles. Lately several spectacular results were reported with sp 3 –sp 3 ‐hybridized diborane(4) and also sp 3 –sp 3 ‐diborane(6) derivatives, but nevertheless their chemistry is still underdeveloped. Braunschweig et al.…”