Starke hyperkonjugative und induktive Effekte auf C‐C‐X‐Bindungswinkel (X = Hauptgruppenelement): Kristallstruktur von Triethylboran und ab‐initio‐Untersuchungen

Abstract

Eher die Ausnahme als die Regel sind ideale Tetraederwinkel in Organoelementverbindungen. Die Abweichungen können beträchtlich sein, wie die Aufweitung des C‐C‐B‐Winkels in Triethylboran auf fast 120° (Strukturbild rechts) zeigt. Dies läßt sich mit einer hyperkonjugativen Wechselwirkung des leeren Bor‐p‐Orbitals mit den bindenden Orbitalen der α‐C‐H‐Bindungen erklären, was durch ab‐initio‐Berechnungen und Strukturbestimmungen anderer Verbindungen mit dem Strukturelement Et‐X (X = Hauptgruppenelement) gestützt wird.

Experimental and Theoretical Studies of the Potential Interconversion of the Amine–Borane iPr2NH·BH(C6F5)2 and the Aminoborane iPr2N=B(C6F5)2 Involving Hydrogen Loss and Uptake

“…The B=N bond length of 1.376(4) Å is within the range formed by unconstrained aminoboranes containing organic substituents at both B and N [1.365(5)-1.441(2) Å]. [67][68][69][70][71][72][73] In addition, this represents a significant length contraction of 15 % from 1, which is consistent with an increase in bond order and change in hybridisation state.…”

1‐Silacyclopent‐2‐enes and 1‐silacyclohex‐2‐enes bearing functionally substituted silyl groups in 2‐positions. Novel electron‐deficient SiHB bridges

“…With the exception of the C14-C15 bond [152.0(5) pm], all other bond lengths and angles are found in the expected range. The elongation of the C14-C15 bond can be explained by the effect of hyperconjugation 32,33 involving this C-C σ bond and the formally empty boron p z orbital, 34,35 in agreement with the arrangement of the 9-BBN group.…”

Agostic Interactions in d0Metal Alkyl Complexes

“…[ 85,86] Comparison of anagostic 14 with its agostic dmpe complex 11, (Figure 8 b), clearly reveals the nature of the interaction. In each case the HOMO represents the TiÀC a s-bonding orbital as described above.…”