Acceptor Strengths of Some Group IV Lewis Acids by Electron Paramagnetic Resonance Studies of Their Complexes with Aliphatic Nitroxides

Allan H. Cohen; Brian M Hoffman

doi:10.1021/ic50136a046

Acceptor Strengths of Some Group IV Lewis Acids by Electron Paramagnetic Resonance Studies of Their Complexes with Aliphatic Nitroxides

Allan H. Cohen, Brian M Hoffman^*

^*Corresponding author for this work

Chemistry

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45 Scopus citations

Abstract

Molecular complexes have been formed between two aliphatic nitroxides, di-tert-butyl nitroxide and 2,2,6,6-tetramethylpiperidine-N-oxyl, and group IV Lewis acids. Analysis of the epr spectra shows that in all cases 1:1 complexes are formed. The π-electron spin density of a nitroxide complex can be analyzed from its epr spectrum and changes in the nitroxide ¹⁴N hfs upon complexation are a measure of the acceptor strength of the Lewis acid. For the acids studied here the order of acceptor strength is TiCl₄ > SnCl₄ > SnBr₄ > SiF₄ ≳ Sn(t-Bu)₂Cr(CO)₅ ≈ SiCl₄ ≳ GeCl₄ ≈ Ti(OPh)₄. In some cases epr spectra show the nitroxide and its complex to be in equilibrium and thermodynamic constants for complex formation are obtained.

Original language	English (US)
Pages (from-to)	1484-1491
Number of pages	8
Journal	Inorganic chemistry
Volume	13
Issue number	6
DOIs	https://doi.org/10.1021/ic50136a046
State	Published - Jun 1 1974

ASJC Scopus subject areas

Physical and Theoretical Chemistry
Inorganic Chemistry

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@article{a8146041fb10428a9f4f71648c1d4046,

title = "Acceptor Strengths of Some Group IV Lewis Acids by Electron Paramagnetic Resonance Studies of Their Complexes with Aliphatic Nitroxides",

abstract = "Molecular complexes have been formed between two aliphatic nitroxides, di-tert-butyl nitroxide and 2,2,6,6-tetramethylpiperidine-N-oxyl, and group IV Lewis acids. Analysis of the epr spectra shows that in all cases 1:1 complexes are formed. The π-electron spin density of a nitroxide complex can be analyzed from its epr spectrum and changes in the nitroxide 14N hfs upon complexation are a measure of the acceptor strength of the Lewis acid. For the acids studied here the order of acceptor strength is TiCl4 > SnCl4 > SnBr4 > SiF4 ≳ Sn(t-Bu)2Cr(CO)5 ≈ SiCl4 ≳ GeCl4 ≈ Ti(OPh)4. In some cases epr spectra show the nitroxide and its complex to be in equilibrium and thermodynamic constants for complex formation are obtained.",

author = "Cohen, {Allan H.} and Hoffman, {Brian M}",

year = "1974",

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journal = "Inorganic chemistry",

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TY - JOUR

T1 - Acceptor Strengths of Some Group IV Lewis Acids by Electron Paramagnetic Resonance Studies of Their Complexes with Aliphatic Nitroxides

AU - Cohen, Allan H.

AU - Hoffman, Brian M

PY - 1974/6/1

Y1 - 1974/6/1

N2 - Molecular complexes have been formed between two aliphatic nitroxides, di-tert-butyl nitroxide and 2,2,6,6-tetramethylpiperidine-N-oxyl, and group IV Lewis acids. Analysis of the epr spectra shows that in all cases 1:1 complexes are formed. The π-electron spin density of a nitroxide complex can be analyzed from its epr spectrum and changes in the nitroxide 14N hfs upon complexation are a measure of the acceptor strength of the Lewis acid. For the acids studied here the order of acceptor strength is TiCl4 > SnCl4 > SnBr4 > SiF4 ≳ Sn(t-Bu)2Cr(CO)5 ≈ SiCl4 ≳ GeCl4 ≈ Ti(OPh)4. In some cases epr spectra show the nitroxide and its complex to be in equilibrium and thermodynamic constants for complex formation are obtained.

AB - Molecular complexes have been formed between two aliphatic nitroxides, di-tert-butyl nitroxide and 2,2,6,6-tetramethylpiperidine-N-oxyl, and group IV Lewis acids. Analysis of the epr spectra shows that in all cases 1:1 complexes are formed. The π-electron spin density of a nitroxide complex can be analyzed from its epr spectrum and changes in the nitroxide 14N hfs upon complexation are a measure of the acceptor strength of the Lewis acid. For the acids studied here the order of acceptor strength is TiCl4 > SnCl4 > SnBr4 > SiF4 ≳ Sn(t-Bu)2Cr(CO)5 ≈ SiCl4 ≳ GeCl4 ≈ Ti(OPh)4. In some cases epr spectra show the nitroxide and its complex to be in equilibrium and thermodynamic constants for complex formation are obtained.

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Acceptor Strengths of Some Group IV Lewis Acids by Electron Paramagnetic Resonance Studies of Their Complexes with Aliphatic Nitroxides

Abstract

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