Recent advances in transition metal diborane(6), diborane(4) and diborene(2) chemistry

Construction of σ-Aromatic AlB2Ring via Borane Coupling with a Dicoordinate Cyclic (Alkyl)(Amino)Aluminyl Anion

“…Note that compound 5 is the first structurally authenticated example of an aluminum complex of diboran(6). 37 The Al−B distances The bonding situation of the AlB 2 unit in 5 was further investigated computationally using the adaptive natural density partitioning (AdNDP) method. 38 The two-center twoelectron (2c-2e) σ-bonding is confirmed at the four exocyclic B−H bonds (Figure S45).…”

Chemistry of Dicationic Diboranes

“…Neutral diboranes with sp 2 -hybridization of the two boron atoms are valuable compounds in modern synthetic chemistry, used extensively as borylation and diboration reagents, some being produced on an industrial scale. [11,27,28] The uncharged three-coordinate boron atom is isoelectronic to the monocationic carbon atom of the same coordination number and, hence, is marked by distinct Lewis acidity. The latter becomes even significantly higher if positively charged boron atoms are introduced, in some cases leading to Lewis super acids.…”

“…Our group introduced in 2018 an electron-rich neutral diborane (4) (11) by adding an organic Lewis base or the inorganic Lewis acid MCl 3 (M = Al or Ga) thus enabling the reactivity study of dicationic sp 2 -hybridized diboranes for the first time (see chapters 4.2 and 5 for more detailed information).…”

“…In line with their monoboron relatives, the reactivity of diborane compounds with an intact B-B bond is mainly determined by the vacant boron p orbitals characterizing them as electrophiles despite the low boron oxidation number. [11] However, the electrophilicity and reactivity of diborane(4) compounds can be effectively diminished by π-donor ligands, making them stable and easy to handle.…”

A Facile Synthesis of Robinson's NHC‐Stabilised Diborane(4)

“…Diboranes [ 1 ] with a boron‐boron single bond, such as the commercially available bis(pinacolato)diboron (B 2 pin 2 ), are commonly employed reagents in synthetic chemistry for numerous borylation reactions, [ 1–4 ] and their further conversion of the resulting C–B fragments allows the transformation into a wide range of functional groups. [ 1,4 ] Diboranes with three‐coordinate boron centres can be activated by the coordination of anionic ligands or neutral σ‐donors, e.g.…”