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Effect of AlH···HO dihydrogen bond on the reaction between diphenylmethanol and pyrazolate‐bridged dialuminum complex. An ONIOM DFT/AM1 study
Author(s) -
Shi FuQiang,
Song BaoAn
Publication year - 2007
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.21573
Subject(s) - oniom , chemistry , molecule , hydrogen bond , computational chemistry , organic chemistry
Abstract To elucidate the nature of the AlH···HO dihydrogen bond and its effect on the reaction between diphenylmethanol and pyrazolate‐bridged dialuminum complex, a theoretical study was carried out using the ONIOM(B3LYP/6‐31+G(d,p):AM1) method. Calculations indicate that this reaction is a two‐step process. The first step is nucleophilic addition and the resulting intermediate is stabilized by an AlH···HO dihydrogen bond. Topology analyses based on the “atoms‐in‐molecules” theory show that the AlH···HO dihydrogen bond in dialuminum intermediate is stronger than normal hydrogen bond. This step is not barrierless, which is contrary to the result predicted by using simplified model. The second step, eliminating a molecule of dihydrogen, requires an activation free energy of 9.9 kcal/mol in gas phase, which implies the simplified model underestimates the energy barrier of this elimination step. ONIOM calculations also show that, using the simplified model without zero‐point energy correction, the dihydrogen bonding strength has been underestimated and unreliable results have been obtained. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008