Solid-state NMR as a spectroscopic tool for characterizing phosphane-borane frustrated lewis pairs

Area of Science:

• Chemistry
• Materials Science

Background:

• Frustrated Lewis pair (FLP) chemistry enables small molecule activation via cooperative Lewis acid-base interactions.
• Intramolecular phosphane-borane adducts are prominent FLPs with tunable catalytic properties.
• Understanding structure-reactivity relationships is crucial for designing effective FLP systems.

Purpose of the Study:

• To review advanced solid-state NMR techniques for characterizing intramolecular phosphane-borane FLPs.
• To connect NMR interaction parameters with structural and bonding information.
• To illustrate the utility of NMR and computational methods for quantifying FLP "frustration" and local geometry.

Main Methods:

• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy, including selective averaging techniques (decoupling/recoupling).
• Ab initio calculations using Density Functional Theory (DFT) methods.
• Analysis of (31)P and (11)B NMR chemical shifts, (11)B electric field gradient tensors, and (31)P-(11)B dipole-dipole interactions.

Main Results:

• Solid-state NMR provides insights into magnetic shielding, quadrupolar coupling, and spin-spin interactions in FLPs.
• Tailoring NMR experiments allows selective probing of specific interactions.
• (31)P and (11)B NMR parameters, alongside DFT, effectively quantify B-P bonding and local structures.

Conclusions:

• Advanced solid-state NMR and DFT calculations offer a powerful strategy for characterizing intramolecular borane-phosphane FLPs.
• This approach enables quantification of the "degree of frustration" and determination of critical structural parameters.
• The methodology aids in understanding and optimizing FLPs for catalytic applications.