The π-Electron-Accepting Ability of the Boron Atom in Ethynylboranes and Related Compounds – An Approximate Weight Computation for Resonance Structures☆
✍ Scribed by Vinzenz Bachler; Nils Metzler-Nolte
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 725 KB
- Volume
- 1998
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
A theoretical analysis was performed to quantify the πelectron-accepting ability of the boron atom in ethynylboranes. An expansion technique was employed which permits to obtain a set of localized bonding schemes and their weights from a delocalized molecular orbital determinantal wavefunction. The derived manifold of bonding schemes is close to the classical resonance hybrid used in organic chemistry (valence-bond description). We quantified the π-electron transfer into the empty π-orbital of the boron atom by investigating nine model compounds where substituents with π-electron-donating ability are adjacent to a boron atom. This led to an ordering of the substituents according to their electron-donating ability towards boron. The boron atom hesitates to accept πelectrons from the ethynyl group in ethynylboranes in particular when good π-donors like amino groups are present. The π-electron donation from the vinyl group to the adjacent boron centre is slightly stronger than from the