Abstract
A recoverable, water soluble, hydrogenation catalyst was synthesized by reacting poly-N-isopropylacrylamide containing a terminal amino group (H2N-CH2CH2-S-pNIPAAm) with [Rh(CO)2Cl]2 in organic solvents to form the square planar rhodium complex (Rh(CO)2Cl(H2N-CH2CH2-S-pNIPAAm)). The catalyst-ligand structure was characterized using in situ multinuclear NMR, XAFS and IR spectroscopic methods. Model complexes containing glycine (H2NCH2COOH), cysteamine (H2NCH2CH2SH) and methionine methyl ester (H2NCH(CH2CH2SCH3)COOCH3) ligands were studied to aid in the interpretation of the coordination sphere of the rhodium catalyst. The spectroscopic data revealed a switch in ligation from the amine bound (Rh-NH2-CH2CH2-S-pNIPAAm) to the thioether bound (Rh-S(-CH2CH2NH2)(-pNIPAAm)) rhodium when the complex was dissolved in water. The evolution of the structure of the rhodium complex dissolved in water was followed by XAFS. The structure changed from the expected monomeric complex to form a rhodium cluster of up to four rhodium atoms containing one SRR′ ligand and one CO ligand per rhodium center. No metallic rhodium was observed during this transformation. The rhodium-rhodium interactions were disrupted when an alkene (3-butenol) was added to the aqueous solution. The kinetics of the hydrogenation reaction were measured using a novel high-pressure flow-through NMR system and the catalyst was found to have a TOF of 3000/Rh/h at 25 °C for the hydrogenation of 3-butenol in water.
| Original language | English |
|---|---|
| Pages (from-to) | 2111-2118 |
| Number of pages | 8 |
| Journal | Journal of Organometallic Chemistry |
| Volume | 693 |
| Issue number | 12 |
| DOIs | |
| Publication status | Published - Jun 1 2008 |
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Keywords
- Aqueous rhodium catalysts
- High pressure NMR
- Homogeneous catalysis
- Recoverable catalyst
- Stimulus sensitive polymers
ASJC Scopus subject areas
- Chemical Engineering (miscellaneous)
- Materials Science (miscellaneous)
- Materials Chemistry
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry
- Biochemistry
Cite this
Structural evolution of a recoverable rhodium hydrogenation catalyst. / Shaw, Wendy J.; Chen, Yongsheng; Fulton, John; Linehan, John; Gutowska, Anna; Bitterwolf, Tom.
In: Journal of Organometallic Chemistry, Vol. 693, No. 12, 01.06.2008, p. 2111-2118.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Structural evolution of a recoverable rhodium hydrogenation catalyst
AU - Shaw, Wendy J.
AU - Chen, Yongsheng
AU - Fulton, John
AU - Linehan, John
AU - Gutowska, Anna
AU - Bitterwolf, Tom
PY - 2008/6/1
Y1 - 2008/6/1
N2 - A recoverable, water soluble, hydrogenation catalyst was synthesized by reacting poly-N-isopropylacrylamide containing a terminal amino group (H2N-CH2CH2-S-pNIPAAm) with [Rh(CO)2Cl]2 in organic solvents to form the square planar rhodium complex (Rh(CO)2Cl(H2N-CH2CH2-S-pNIPAAm)). The catalyst-ligand structure was characterized using in situ multinuclear NMR, XAFS and IR spectroscopic methods. Model complexes containing glycine (H2NCH2COOH), cysteamine (H2NCH2CH2SH) and methionine methyl ester (H2NCH(CH2CH2SCH3)COOCH3) ligands were studied to aid in the interpretation of the coordination sphere of the rhodium catalyst. The spectroscopic data revealed a switch in ligation from the amine bound (Rh-NH2-CH2CH2-S-pNIPAAm) to the thioether bound (Rh-S(-CH2CH2NH2)(-pNIPAAm)) rhodium when the complex was dissolved in water. The evolution of the structure of the rhodium complex dissolved in water was followed by XAFS. The structure changed from the expected monomeric complex to form a rhodium cluster of up to four rhodium atoms containing one SRR′ ligand and one CO ligand per rhodium center. No metallic rhodium was observed during this transformation. The rhodium-rhodium interactions were disrupted when an alkene (3-butenol) was added to the aqueous solution. The kinetics of the hydrogenation reaction were measured using a novel high-pressure flow-through NMR system and the catalyst was found to have a TOF of 3000/Rh/h at 25 °C for the hydrogenation of 3-butenol in water.
AB - A recoverable, water soluble, hydrogenation catalyst was synthesized by reacting poly-N-isopropylacrylamide containing a terminal amino group (H2N-CH2CH2-S-pNIPAAm) with [Rh(CO)2Cl]2 in organic solvents to form the square planar rhodium complex (Rh(CO)2Cl(H2N-CH2CH2-S-pNIPAAm)). The catalyst-ligand structure was characterized using in situ multinuclear NMR, XAFS and IR spectroscopic methods. Model complexes containing glycine (H2NCH2COOH), cysteamine (H2NCH2CH2SH) and methionine methyl ester (H2NCH(CH2CH2SCH3)COOCH3) ligands were studied to aid in the interpretation of the coordination sphere of the rhodium catalyst. The spectroscopic data revealed a switch in ligation from the amine bound (Rh-NH2-CH2CH2-S-pNIPAAm) to the thioether bound (Rh-S(-CH2CH2NH2)(-pNIPAAm)) rhodium when the complex was dissolved in water. The evolution of the structure of the rhodium complex dissolved in water was followed by XAFS. The structure changed from the expected monomeric complex to form a rhodium cluster of up to four rhodium atoms containing one SRR′ ligand and one CO ligand per rhodium center. No metallic rhodium was observed during this transformation. The rhodium-rhodium interactions were disrupted when an alkene (3-butenol) was added to the aqueous solution. The kinetics of the hydrogenation reaction were measured using a novel high-pressure flow-through NMR system and the catalyst was found to have a TOF of 3000/Rh/h at 25 °C for the hydrogenation of 3-butenol in water.
KW - Aqueous rhodium catalysts
KW - High pressure NMR
KW - Homogeneous catalysis
KW - Recoverable catalyst
KW - Stimulus sensitive polymers
UR - http://www.scopus.com/inward/record.url?scp=43449121221&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=43449121221&partnerID=8YFLogxK
U2 - 10.1016/j.jorganchem.2008.03.011
DO - 10.1016/j.jorganchem.2008.03.011
M3 - Article
VL - 693
SP - 2111
EP - 2118
JO - Journal of Organometallic Chemistry
JF - Journal of Organometallic Chemistry
SN - 0022-328X
IS - 12
ER -