Ein planares, aromatischesbicyclo-Tetraboran(4)

Abstract

Bei der Reduktion von Dimethylaminodichlorboran und Dimethylaminodichlordiboran(4) mit NaK2.8‐Legierung wurde das neue Tetraboran(4) 1 erhalten (siehe Schema). Die ungewöhnliche Bindungssituation in 1 wird anhand von Molekülorbitalrechnungen veranschaulicht.

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

“…Known tetraorganyltetraboranes(4) 1 a and 1 b have a tetrahedral structure,1, 2 the recently described planar 1,3‐diamino‐2,4‐diboryltetraborane(4) 2 a 3 is diamond‐shaped with edges of about equal length (Scheme ). We present here compound 2 b , a tetraalkyltetraborane(4) with a distorted diamond‐shaped structure (Scheme ).…”

“… Known tetrahedral tetraorganyltetraboranes(4) 1 a (R= t Bu)1 and 1 b (R=2,4,6‐trimethylphenyl),2 the planar tetraborane(4) 2 a ,3 as well as the unknown pentaborane(7) 3 a . The ellipse denotes two cyclically delocalized π electrons.…”

Aromatic Boranes with Planar-Tetracoordinate Boron Atoms and Very Short B−B Distances

“…The bonding 1,3‐interaction is further strengthened by a 4c2e π bond, whose electrons according to the NBO analysis are preferentially (36 % each) localized on the boron centers of the short diagonal. In contrast, additional σ electrons must occupy molecular orbitals with 1,3‐antibonding character 16. This explanation is supported by the fact that the B⋅⋅⋅B distance in 9 (165.2 pm) with six σ framework electrons is significantly longer than in 8 and 3 (150.9 and 153.0 pm, respectively) with four σ framework electrons each.…”

Two-electron aromatics containing three and four adjacent boron atoms

“…As a first experimental approach to compounds of type 2, the boryl-bridged 2a was obtained recently by addition of 4-t-butylpyridine to the first repre-sentative of two-electron aromatic tetraboranes(6) with nonclassical σ-bonds, 3 [10]. A first derivative of the corresponding two-electron aromatic tetraborane(4) 4 was also presented [11].…”