Solid-State Nuclear Magnetic Resonance Techniques for the Structural Characterization of Geminal Alane-Phosphane Frustrated Lewis Pairs and Secondary Adducts

Author(s)

Wuebker, Anna-Lena ^[1] ; Koppe, Jonas ^[1] ; Bradtmueller, Henrik ^{[1, 2]} ; Keweloh, Lukas ^[3] ; Pleschka, Damian ^[3] ; Uhl, Werner ^[3] ; Hansen, Michael Ryan ^[1] ; Eckert, Hellmut ^{[4, 1]}

Affiliation

^[1] WWU Munster, Inst Phys Chem, Corrensstr 28-30, D-48149 Munster - Germany

^[2] Univ Fed Sao Carlos, Vitreous Mat Lab, Dept Mat Engn, CP 676, BR-13565905 Sao Carlos, SP - Brazil

^[3] WWU Munster, Inst Anorgan & Analyt Chem, Corrensstr 28-30, D-48149 Munster - Germany

^[4] Univ Sao Paulo, Inst Fis Sao Carlos, BR-13566590 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: CHEMISTRY-A EUROPEAN JOURNAL; v. 27, n. 52 AUG 2021.
• Web of Science Citations: 0

Abstract

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 Al-27-P-31 spin-spin coupling constants, and Al-27 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 P-31 NMR chemical shifts for the studied Al/P FLPs are very sensitive to slight structural inequivalences. The Al-27 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 Al-27 wideband uniform rate smooth truncation (WURST) Carr-Purcell-Meiboom-Gill (WCPMG) NMR experiment. Al-27 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 angstrom. (AU)

• FAPESP's process: 13/07793-6 - CEPIV - Center for Teaching, Research and Innovation in Glass
• Grantee: Edgar Dutra Zanotto
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC
• FAPESP's process: 19/26399-3 - Elucidating structural rearrangements during glass relaxation and crystallization
• Grantee: Henrik Bradtmüller
• Support Opportunities: Scholarships in Brazil - Post-Doctoral