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Dynamic/Thermochemical Balance Drives Unusual Alkyl/F Exchange Reactions in Siloxides and Analogs

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Autor(es):
Correra, Thiago C. [1] ; Fernandes, Andre S. [1] ; Riveros, Jose M. [1]
Número total de Autores: 3
Afiliação do(s) autor(es):
[1] Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05508000 Sao Paulo - Brazil
Número total de Afiliações: 1
Tipo de documento: Artigo Científico
Fonte: Journal of Physical Chemistry A; v. 120, n. 10, p. 1644-1651, MAR 17 2016.
Citações Web of Science: 0
Resumo

A recent report has shown that siloxides can undergo an unusual Me/F exchange reaction promoted by NF3 in the gas phase (Angew. Chem. Int. Ed. 2012, SI, 8632-8635). A more extensive study of this kind of exchange has been carried out using mass spectrometry techniques (FT-ICR), DFT calculations, natural bond orbital (NBO) analysis, and Born-Oppenheimer molecular dynamics simulations (BOMD), using NF3, SO2F2, and CF4 as fluorine donors and evaluating the effect of replacing the Si center by Ge and C. This comprehensive approach shows that NF3 is crucial for the exchange reaction, as SO2F2 forms SO3F- via a pentacoordinated channel whereas no reaction is observed for CF4. The uniqueness of NF3 is caused by favorable thermochemical consideration and by dynamic effects that preclude the formation of the ubiquitous Si-F pentacoordinated species. Me3GeO- was shown to be as reactive as siloxides toward NF3, whereas C analogs showed no reactions under our experimental conditions. The exchange reaction was also shown to take place for triethylsiloxides. These exchange reactions are examples of reaction systems that avoid the lower energy pathway and are driven by dynamic effects that cannot be explained by the potential energy surface. (AU)

Processo FAPESP: 14/15962-5 - Mecanismos de reação de sistemas catalíticos assimétricos por espectrometria de massas e espectroscopia vibracional de íons na fase gasosa
Beneficiário:Thiago Carita Correra
Linha de fomento: Auxílio à Pesquisa - Apoio a Jovens Pesquisadores