Premium
Solid‐State Nuclear Magnetic Resonance Techniques for the Structural Characterization of Geminal Alane‐Phosphane Frustrated Lewis Pairs and Secondary Adducts
Author(s) -
Wübker AnnaLena,
Koppe Jonas,
Bradtmüller Henrik,
Keweloh Lukas,
Pleschka Damian,
Uhl Werner,
Hansen Michael Ryan,
Eckert Hellmut
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202102113
Subject(s) - geminal , chemistry , chemical shift , quadrupole , coupling constant , frustrated lewis pair , nuclear magnetic resonance crystallography , nuclear magnetic resonance spectroscopy , solid state nuclear magnetic resonance , nuclear quadrupole resonance , density functional theory , nuclear magnetic resonance , computational chemistry , fluorine 19 nmr , stereochemistry , atomic physics , lewis acids and bases , physics , organic chemistry , catalysis , particle physics
The first comprehensive solid‐state nuclear magnetic resonance (NMR) characterization of geminal alane‐phosphane frustrated Lewis pairs (Al/P FLPs) is reported. Their relevant NMR parameters (isotropic chemical shifts, direct and indirect 27 Al‐ 31 P spin‐spin coupling constants, and 27 Al nuclear electric quadrupole coupling tensor components) have been determined by numerical analysis of the experimental NMR line shapes and compared with values computed from the known crystal structures by using density functional theory (DFT) methods. Our work demonstrates that the 31 P NMR chemical shifts for the studied Al/P FLPs are very sensitive to slight structural inequivalences. The 27 Al NMR central transition signals are spread out over a broad frequency range (>200 kHz), owing to the presence of strong nuclear electric quadrupolar interactions that can be well‐reproduced by the static 27 Al wideband uniform rate smooth truncation (WURST) Carr‐Purcell‐Meiboom‐Gill (WCPMG) NMR experiment. 27 Al chemical shifts and quadrupole tensor components offer a facile and clear distinction between three‐ and four‐coordinate aluminum environments. For measuring internuclear Al⋅⋅⋅P distances a new resonance‐echo saturation‐pulse double‐resonance (RESPDOR) experiment was developed by using efficient saturation via frequency‐swept WURST pulses. The successful implementation of this widely applicable technique indicates that internuclear Al⋅⋅⋅P distances in these compounds can be measured within a precision of ±0.1 Å.