One-Electron Bonds in Frustrated Lewis Pair TPB Ligands: Boron Behaving as a Lewis Base

Angewandte Chemie - International Edition

5 years ago

One-Electron Bonds in Frustrated Lewis Pair TPB Ligands: Boron Behaving as a Lewis Base

M. Merced Montero-Campillo, Elena Kusevska, Otilia Mó, Manuel Yáñez

Owing to its versatility in synthetic chemistry, TPB (tris[2-diisopropylphospino)phenyl]borane) is a very important frustrated Lewis Pair. The unusual stability of the neutral radical (TPB)Cu has been related to the presence of a one-electron B−Cu bond. Herein we show, through the use of different computational chemistry methods, that the existence and nature of this kind of A⋅⋅⋅M bond (A=donor atom, M=transition metal) depends on the surrounding chemical structure, and can be genuine one-electron sigma bonds only if appropriate metal ligands (Y), able to trap the charge in the desired region, are chosen. This ability is modulated by the subtle balance between the electronegativity of the different atoms along the A⋅⋅⋅M⋅⋅⋅Y bond paths. Most importantly, contrary to many TPB complexes in which boron acts as a Lewis acid, in one-electron-bond-containing structures boron behaves as a Lewis base. Basic instinct: In a frustrated Lewis Pair, such as the TPB ligand, boron usually accepts charge from the metal. However, in one-electron-bond-containing structures, boron behaves as a Lewis base. Computational chemistry methods are used to explain the chemical structure needed to observe such a behavior.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/anie.201701161