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Measurement of Aluminum–Carbon Distances Using S‐RESPDOR NMR Experiments
Author(s) -
Pourpoint Frédérique,
Trébosc Julien,
Gauvin Régis M.,
Wang Qiang,
Lafon Olivier,
Deng Feng,
Amoureux JeanPaul
Publication year - 2012
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201200490
Subject(s) - heteronuclear molecule , dephasing , chemistry , analytical chemistry (journal) , saturation (graph theory) , pulse sequence , nuclear magnetic resonance spectroscopy , spectroscopy , molecular physics , nuclear magnetic resonance , physics , stereochemistry , mathematics , combinatorics , chromatography , quantum mechanics
Abstract It is demonstrated that reliable aluminum–carbon distances can be measured in samples with 13 C natural abundance by NMR spectroscopy. Overcoupled resonators, with only one radio‐frequency synthesizer and one amplifier, are used to irradiate in the same pulse sequence 27 Al and 13 C nuclei, which differ by only 3.6 % in Larmor frequencies. The combination of 27 Al saturation pulse with heteronuclear dipolar recoupling yields dipolar dephasing of the 13 C signal, which only depends on the AlC distance and the efficiency of the saturation pulse. Therefore, reliable distances can be obtained by rapid fitting of experimental data to an analytical expression. It is demonstrated that with natural isotopic abundance this approach allows recovery of AlC distances of 216 pm for the covalent bond in lithium tetraalkyl aluminates, commonly used as a co‐catalyst in olefin polymerization processes, and which range from 274 to 381 pm for the three carbon atoms in aluminum lactate. The accuracy of the measured internuclear distances is carefully estimated.