Abstract
A series of [Rh(PCH2XRCH2P)2]+ complexes was prepared to investigate second and outer coordination sphere effects on CO2 hydrogenation catalysis, where X is CH2 (dppp) or X-R is N-CH3, N-CH2COOH (glycine), N-CH2COOCH3 (Gly-OMe), or N-CH2C(O)N-CH(CH3)COOCH3 (GlyAla-OMe). All of these complexes were active for CO2 reduction to formate, with the N-CH3 derivative offering an 8-fold enhancement over the dppp derivative, which is consistent with increased electron density around the metal. Despite the increase in rate with the addition of the pendant nitrogen, the addition of electron withdrawing amino acids and dipeptides to the amine resulted in complexes with reductions in rate of 1 to 2 orders of magnitude, most consistent with a change in pKa of the pendant amine, resulting in lower activity. Collectively, the data suggest multiple contributions of the pendant amine in this catalytic system.
| Original language | English |
|---|---|
| Pages (from-to) | 3663-3670 |
| Number of pages | 8 |
| Journal | ACS Catalysis |
| Volume | 4 |
| Issue number | 10 |
| DOIs | |
| Publication status | Published - Oct 3 2014 |
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Keywords
- amino acid catalysts
- CO hydrogenation
- homogeneous catalysis
- in situ NMR
- outer coordination sphere
ASJC Scopus subject areas
- Catalysis
Cite this
The influence of the second and outer coordination spheres on Rh(diphosphine)2 CO2 hydrogenation catalysts. / Bays, J. Timothy; Priyadarshani, Nilusha; Jeletic, Matthew S.; Hulley, Elliot B.; Miller, Deanna L.; Linehan, John; Shaw, Wendy J.
In: ACS Catalysis, Vol. 4, No. 10, 03.10.2014, p. 3663-3670.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - The influence of the second and outer coordination spheres on Rh(diphosphine)2 CO2 hydrogenation catalysts
AU - Bays, J. Timothy
AU - Priyadarshani, Nilusha
AU - Jeletic, Matthew S.
AU - Hulley, Elliot B.
AU - Miller, Deanna L.
AU - Linehan, John
AU - Shaw, Wendy J.
PY - 2014/10/3
Y1 - 2014/10/3
N2 - A series of [Rh(PCH2XRCH2P)2]+ complexes was prepared to investigate second and outer coordination sphere effects on CO2 hydrogenation catalysis, where X is CH2 (dppp) or X-R is N-CH3, N-CH2COOH (glycine), N-CH2COOCH3 (Gly-OMe), or N-CH2C(O)N-CH(CH3)COOCH3 (GlyAla-OMe). All of these complexes were active for CO2 reduction to formate, with the N-CH3 derivative offering an 8-fold enhancement over the dppp derivative, which is consistent with increased electron density around the metal. Despite the increase in rate with the addition of the pendant nitrogen, the addition of electron withdrawing amino acids and dipeptides to the amine resulted in complexes with reductions in rate of 1 to 2 orders of magnitude, most consistent with a change in pKa of the pendant amine, resulting in lower activity. Collectively, the data suggest multiple contributions of the pendant amine in this catalytic system.
AB - A series of [Rh(PCH2XRCH2P)2]+ complexes was prepared to investigate second and outer coordination sphere effects on CO2 hydrogenation catalysis, where X is CH2 (dppp) or X-R is N-CH3, N-CH2COOH (glycine), N-CH2COOCH3 (Gly-OMe), or N-CH2C(O)N-CH(CH3)COOCH3 (GlyAla-OMe). All of these complexes were active for CO2 reduction to formate, with the N-CH3 derivative offering an 8-fold enhancement over the dppp derivative, which is consistent with increased electron density around the metal. Despite the increase in rate with the addition of the pendant nitrogen, the addition of electron withdrawing amino acids and dipeptides to the amine resulted in complexes with reductions in rate of 1 to 2 orders of magnitude, most consistent with a change in pKa of the pendant amine, resulting in lower activity. Collectively, the data suggest multiple contributions of the pendant amine in this catalytic system.
KW - amino acid catalysts
KW - CO hydrogenation
KW - homogeneous catalysis
KW - in situ NMR
KW - outer coordination sphere
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U2 - 10.1021/cs5009199
DO - 10.1021/cs5009199
M3 - Article
VL - 4
SP - 3663
EP - 3670
JO - ACS Catalysis
JF - ACS Catalysis
SN - 2155-5435
IS - 10
ER -