Synthesis, mechanism studies of rhodium complexes and electrochemical oxidation, spectroscopic properties of phenol derivatives

A series of rare five-coordinate organorhodium(III) intermediates [Rh(N^C)(PAr3)2CH=CHR]PF6 (N^C = benzo[h,f]quinoline, benzo[h]quinoline, 2-phenylpyridine, R = para-Ph-(SO2CF3, CF3, NO2, Cl, F, H, CH3, OCH3), CH2Ph, CH2CH2Ph, Ar = para-Ph-(OCH3, CH3, F)) and subsequent C–C coupling rhodium(I) compl...

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Main Author: Chen, Shan Shan
Other Authors: Li Xingwei
Format: Theses and Dissertations
Language:English
Published: 2011
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Online Access:https://hdl.handle.net/10356/46283
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-462832023-02-28T23:32:00Z Synthesis, mechanism studies of rhodium complexes and electrochemical oxidation, spectroscopic properties of phenol derivatives Chen, Shan Shan Li Xingwei Richard David Webster School of Physical and Mathematical Sciences DRNTU::Science::Chemistry A series of rare five-coordinate organorhodium(III) intermediates [Rh(N^C)(PAr3)2CH=CHR]PF6 (N^C = benzo[h,f]quinoline, benzo[h]quinoline, 2-phenylpyridine, R = para-Ph-(SO2CF3, CF3, NO2, Cl, F, H, CH3, OCH3), CH2Ph, CH2CH2Ph, Ar = para-Ph-(OCH3, CH3, F)) and subsequent C–C coupling rhodium(I) complexes [Rh(N^C–CH=CHR)(PAr3)2]PF6 have been isolated and fully characterized. The total mechanism of C–H activation and subsequent C–C reductive elimination from the rhodium center has been proposed and the electronic effects of reactive ligands CH=CHAr and ancillary ligands PAr3 on the rate of the C–C reductive elimination reactions from the five-coordinate intermediates were studied. The absolute rate of C–C reductive elimination has been measured and the rate decrease as the vinyl ligands with more electron-withdrawing groups and the ancillary ligands PAr3 with more electron-donating groups. We also measured the kinetics in different solvents like CD2Cl2, THF-d8 and acetone-d6 in order to probe the impact of the solvent’s polarity and donating ability on the rate of the reaction. The result shows that the coordinated solvent can accelerate the rate of reductive elimination step. Chelation-assisted activation of C–X bonds (X = Cl, Br, and I) took place in the reaction of [Rh(PPh3)2(acetone)2]PF6 and 2-(2-halophenyl)pyridine or 10-halobenzo[h]quinoline. A series of 16-electron five-coordinate cationic rhodium(III) monohalide complexes was synthesized at room temperature. Neutral octahedral rhodium(III) dihalide complexes were obtained when the corresponding cationic monohalide complexes were further heated in acetone. Rhodium and iridium diiodides with these cyclometalation motifs could be alternatively synthesized from the reaction of the corresponding cyclometalated hydride complexes and I2. X-ray crystal structures of representative monohalide and dihalide complexes are reported. Octahedral rhodium(III) dihalide complexes are active catalysts for the dimerization of terminal alkynes, while 16-electron cationic rhodium(III) monohalides are inactive. DOCTOR OF PHILOSOPHY (SPMS) 2011-11-28T06:59:12Z 2011-11-28T06:59:12Z 2011 2011 Thesis Chen, S. S. (2011). Synthesis, mechanism studies of rhodium complexes and electrochemical oxidation, spectroscopic properties of phenol derivatives. Doctoral thesis, Nanyang Technological University, Singapore. https://hdl.handle.net/10356/46283 10.32657/10356/46283 en 228 p. application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic DRNTU::Science::Chemistry
spellingShingle DRNTU::Science::Chemistry
Chen, Shan Shan
Synthesis, mechanism studies of rhodium complexes and electrochemical oxidation, spectroscopic properties of phenol derivatives
description A series of rare five-coordinate organorhodium(III) intermediates [Rh(N^C)(PAr3)2CH=CHR]PF6 (N^C = benzo[h,f]quinoline, benzo[h]quinoline, 2-phenylpyridine, R = para-Ph-(SO2CF3, CF3, NO2, Cl, F, H, CH3, OCH3), CH2Ph, CH2CH2Ph, Ar = para-Ph-(OCH3, CH3, F)) and subsequent C–C coupling rhodium(I) complexes [Rh(N^C–CH=CHR)(PAr3)2]PF6 have been isolated and fully characterized. The total mechanism of C–H activation and subsequent C–C reductive elimination from the rhodium center has been proposed and the electronic effects of reactive ligands CH=CHAr and ancillary ligands PAr3 on the rate of the C–C reductive elimination reactions from the five-coordinate intermediates were studied. The absolute rate of C–C reductive elimination has been measured and the rate decrease as the vinyl ligands with more electron-withdrawing groups and the ancillary ligands PAr3 with more electron-donating groups. We also measured the kinetics in different solvents like CD2Cl2, THF-d8 and acetone-d6 in order to probe the impact of the solvent’s polarity and donating ability on the rate of the reaction. The result shows that the coordinated solvent can accelerate the rate of reductive elimination step. Chelation-assisted activation of C–X bonds (X = Cl, Br, and I) took place in the reaction of [Rh(PPh3)2(acetone)2]PF6 and 2-(2-halophenyl)pyridine or 10-halobenzo[h]quinoline. A series of 16-electron five-coordinate cationic rhodium(III) monohalide complexes was synthesized at room temperature. Neutral octahedral rhodium(III) dihalide complexes were obtained when the corresponding cationic monohalide complexes were further heated in acetone. Rhodium and iridium diiodides with these cyclometalation motifs could be alternatively synthesized from the reaction of the corresponding cyclometalated hydride complexes and I2. X-ray crystal structures of representative monohalide and dihalide complexes are reported. Octahedral rhodium(III) dihalide complexes are active catalysts for the dimerization of terminal alkynes, while 16-electron cationic rhodium(III) monohalides are inactive.
author2 Li Xingwei
author_facet Li Xingwei
Chen, Shan Shan
format Theses and Dissertations
author Chen, Shan Shan
author_sort Chen, Shan Shan
title Synthesis, mechanism studies of rhodium complexes and electrochemical oxidation, spectroscopic properties of phenol derivatives
title_short Synthesis, mechanism studies of rhodium complexes and electrochemical oxidation, spectroscopic properties of phenol derivatives
title_full Synthesis, mechanism studies of rhodium complexes and electrochemical oxidation, spectroscopic properties of phenol derivatives
title_fullStr Synthesis, mechanism studies of rhodium complexes and electrochemical oxidation, spectroscopic properties of phenol derivatives
title_full_unstemmed Synthesis, mechanism studies of rhodium complexes and electrochemical oxidation, spectroscopic properties of phenol derivatives
title_sort synthesis, mechanism studies of rhodium complexes and electrochemical oxidation, spectroscopic properties of phenol derivatives
publishDate 2011
url https://hdl.handle.net/10356/46283
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