Topomerization of a Distorted Diamond‐Shaped Tetraborane(4) and Its Hydroboration to a closo‐Pentaborane(7) with a nido Structure

Abstract

The exchange of the short and long diagonal of the B4 diamond of 1 is the simplest variant to date of the diamond–square–diamond rearrangement, which plays a central role in the isomerization of polyhedral boranes, carboranes, and metallaboranes. Compound 2, which is readily accessible from 1, is the first derivative of pentaborane(7).

Electron‐Deficient Triborane and Tetraborane Ring Compounds: Synthesis, Structure, and Bonding

“…They also showed that the hydrogenation of diboretes with H 2 /Pd yielded 1,3-diboretanes (CHR 1 ) 2 (BR 2 ) 2 (e.g. [61,62] Reduction and chloride abstraction from aparticular dichlorotetraborane(6) led to aneutral tetraborane(4), [63] which was eventually further reduced to a( B 4 H 4 ) 2À derivative (Scheme 12 c). [60] Diboretes (CR 3 ) 2 (BtBu) 2 with R 3 = Me,E t, CH 2 tBu, or SiMe 3 (Scheme 12 b) as well as (CtBu) 2 (BMe) 2 were synthesized by Berndt and co-workers,and then reduced with K/Na to radical monoanions.…”

“…[74] Thee lectronic structure and bond parameters of tetrahedral B 4 H 4 were studied in several theoretical studies, [75] and the bonding could be described in terms of four (3c,2e)b onds.H ence,e ach boron atom participates in four bonds:o ne (2c,2e)t erminal bond (B À H) and three (3c,2e) bonds with the other boron atoms.E PR measurements suggest that B 4 (tBu) 4 can be reduced with Na/K to ar adical monoanion. [63,70] Thec ompound B 4 (NMe 2 ) 2 [(B(NMe 2 ) 2 ] 2 reported by Siebert and co-workers [70] is the product of the reduction of am ixture of dichloro(methyl)borane and dichlorobis(dimethylamino)diborane(4). [63,70] Thec ompound B 4 (NMe 2 ) 2 [(B(NMe 2 ) 2 ] 2 reported by Siebert and co-workers [70] is the product of the reduction of am ixture of dichloro(methyl)borane and dichlorobis(dimethylamino)diborane(4).…”

Four Boron Atoms, Four Positive Charges, and Four Skeletal Electrons: A Fluorescent σ‐Aromatic Tetraborane(4)

“…Siebert et al reported 1984 ad erivative of the isoelectronic neutral C 2 B 2 H 4 ,w ith amino groups in place for hydrides at the boron atoms. [7,8] Scheme 1shows the derivative [B 4 [B(NMe 2 ) 2 ] 2 (NMe) 2 ]. [6] Formal two-electron oxidation of [B 4 H 4 ] 2À leads to neutral B 4 H 4 with aplanar rhomboid B 4 core and delocalized s-and p-systems.…”

Vier Boratome, vier positive Ladungen und vier Gerüstelektronen: ein fluoreszierendes σ‐aromatisches Tetraboran(4)

“…Siebert et al berichteten bereits 1984 von einem Derivat des isoelektronischen, neutralen C 2 B 2 H 4 mit Aminogruppen anstelle der borgebundenen Hydride. [7,8] (6) mit einem planaren, rhomboiden B 4 -Gerüst und 6GE. [6] Eine Zwei-Elektronen-Oxidation von [B 4 H 4 ] 2À führt formal zu neutralem B 4 H 4 mit einem planaren rhomboiden B 4 -Gerüst und delokalisierten s-u nd p-Systemen.…”

“…[9] Das weitere Entfernen von zwei Elektronen würde letztlich das Te trakation [B 4 H 4 ] 4+ mit nur 4GE ergeben. [11][12][13] Das Dihydrido-Diboran [HB(hpp)] 2 (1;h pp = 1,3,4,6,7,pyrimidinat;Schema 2a)ist ein besonders elektronenreiches Beispiel. Die vier Gerüstelektronen bieten keine ausreichende Bindungsenergie,u m die massive Coulomb-Abstoßung zwischen den vier HB + -Einheiten zu kompensieren ("Coulomb-Explosion").…”