Journal of the American Chemical Society
Article
1.48 (m), 1.25 (dd, J = 12.2, 9H), 1.24 (dd, J = 13.1, 9H), 1.17 (d, J =
12.0, 9H), 1.15 (d, J = 12.3, 9H), −10.47 (ddd, J = 23.4, 19.0, 5.0 Hz,
1H), −12.20 (ddt, J = 38.7, 5.9, 5.2 Hz, 1H), −15.72 (dd, J = 30.1, 5.1
Hz, 1H). 31P{1H} NMR (162 MHz; C6D6): δ 113.6, 98.7.
of 1.89 kcal/mol. The standard state correction for ethyl acetate was
3.27 kcal/mol when the ester was both the substrate and the solvent, in
Schemes 9−13. All organic molecules (acetaldehyde, ethanol, ethyl
acetate, 1-ethoxyethanol) and TS9 were optimized using the M06-L/
def2-QZVP and M06-2X/def2-QZVP methods, followed by frequency
calculations at the same level of theory. The nature of the following
transition states TS2, TS4, TS5, and TS11 was confirmed by intrinsic
reaction coordinate (IRC) calculations. Dynamics has not been taken
into account when modeling the structures with the explicit, hydrogen-
bonded ethanol.
NMR Data for 7. 1H NMR (300 MHz; THF-d8, −30 °C): δ 7.94 (d,
J = 5.5 Hz, 1H), 7.83 (d, J = 6.0 Hz, 1H), 7.06 (t, J = 7.6 Hz, 1H), 6.94
(t, J = 7.6 Hz, 1H), 6.80 (d, J = 8.2 Hz, 1H), 6.74 (d, J = 8.2 Hz, 1H),
6.68 (m, 2H), 6.65 (d, J = 6.7 Hz, 1H), 6.58 (d, J = 8.5 Hz, 1H), 6.47 (d,
J = 7.1 Hz, 1H), 6.40 (t, J = 6.3 Hz, 1H), 6.01 (m, 2H), 3.21 (dd, J =
11.4, 15.5 Hz, 1H), 3.07 (dd, J = 11.4, 15.6 Hz, 1H), 2.49 (dd, J = 7.9,
15.5 Hz, 1H), 2.37 (dd, J = 6.7, 15.6 Hz, 1H), 1.60 (d, J = 12.0 Hz,
CH3), 1.25 (br, CH3), 1.07 (br, CH3), 0.86 (d, J = 11.5 Hz, CH3),
−13.40 (ddd, J = 2.4, 16.0, 23.7 Hz, 1H), −20.05 (ddd, J = 4.3, 12.1,
16.0 Hz, 1H). 31P{1H} NMR (121 MHz; THF-d8): δ 104.8 (s), 122.7
(s).
ASSOCIATED CONTENT
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sı
* Supporting Information
The Supporting Information is available free of charge at
NMR Data for 9 (Main Species) Formed upon Dissolving 5 in
1
Ethanol-d6. H NMR (400 MHz; ethanol-d6): δ 9.01 (m, 1H, Py),
Representative NMR spectra, computed energies, and a
summary of the crystal data collection and refinement
parameters for 5, 6, and 7 (PDF)
7.84 (td, J = 7.8, 1.6 Hz, 1H, Py), 7.34 (overlapped m, 2H, Py), 3.98 (d, J
= 11.6 Hz, 1H, NCH), 3.06 (t, J = 11.6 Hz, 1H, NCH), 2.40−1.63 (m,
8H, CH2), 1.38 (d, J = 13.2 Hz, 9H, CH3), 1.35 (d, J = 13.2 Hz, 9H,
CH3), −16.68 (d, J = 26 Hz, 1H). 13C{1H} NMR (100 MHz; ethanol-
d6): δ 206.5 (d, J = 15.7 Hz, CO), 164.6, 153.5, 137.7, 124.0, 121.8 (Py),
69.0 (d, J = 2.9 Hz, NCH), 65.1 (m, NCH), 38.0 (d, J = 14.7 Hz, C, t-
Bu), 37.6 (d, J = 23.9 Hz, C, t-Bu), 34.4 (d, J = 15.1 Hz, CH2), 32.3 (d, J
= 11.9 Hz, CH2), 30.4 (d, J = 4.6 Hz, CH3, t-Bu), 30.3 (d, J = 3.4 Hz,
CH3, t-Bu), 28.2 (s, CH2), 25.4 (s, CH2). Resonances of the
Ru(OC2D5) group were not observed due to exchange with the
solvent. 31P{1H} NMR (162 MHz; ethanol-d6): δ 98.5 (s).
NMR Data for 10 Formed on Heating 2 in EtOH for 6 h at 80
°C. 1H NMR (400 MHz; EtOH): δ 9.00 (m, 1H, Py), 7.84 (td, J = 7.8,
1.6 Hz, 1H, Py), 7.34 (overlapped m, 2H, Py), 3.99 (d, 3J = 11.2 Hz, 1H,
NCH), 3.05 (t, 3J = 12.2 Hz, 1H, NCH), 2.44−1.63 (m, 8H, CH2), 1.35
(d, 3J = 12.8 Hz, 9H, CH3), 1.31 (d, 3J = 13.0 Hz, 9H, CH3), −17.56 (d,
2J = 26.4 Hz, 1H). 13C{1H} NMR (100 MHz; EtOH): δ 205 (d, 2J =
14.9 Hz, CO), 181.9 (s, OAc), 164.4, 153.7, 137.5, 124.0, 120.9 (Py),
68.1 (d, J = 3.1 Hz, NCH), 64.1 (d, J = 2.6 Hz, NCH), 37.2 (d, J = 23.7
Hz, C, t-Bu), 37.0 (d, J = 15.3 Hz, C, t-Bu), 34.3 (d, J = 15.7 Hz, CH2),
32.3 (d, J = 12.1 Hz, CH2), 29.7 (d, J = 3.3 Hz, CH3, t-Bu), 29.4 (d, J =
4.5 Hz, CH3, t-Bu), 28.4 (s, CH2), 24.9 (s, CH2), 25.4 (s, OAc).
31P{1H} NMR (162 MHz; ethanol-d6): δ 100.1 (s)
Hydrogenation. The hydrogenations of ethyl acetate and methyl
hexanoate were performed in a 300 mL stainless-steel Parr reactor.
Inside an argon glovebox, the required quantities of the catalysts (9−10
mg) were weighed out on a calibrated analytical balance accurate to 0.1
mg. A balance accurate to 1 mg was used for taking 0.2 mol of the esters
(prior to weighing, the ester substrate was allowed to pass through a
layer of activated basic alumina). The reactor was loaded with a 0.95 cm
× 2.54 cm SCIENCEWARE rare-earth magnet spinbar, the catalyst,
and the ester substrate; it was assembled inside the glovebox, then taken
outside and pressurized under H2 to 50 bar. The pressurized reactor was
disconnected from the H2 tank and placed into an oil bath preheated to
100 °C on a hot plate stirrer. This temperature was maintained for 3 h
while magnetically stirring at 500 rpm.
Computational Details. All calculated ruthenium species of this
paper possess a zero net charge. The DFT calculations were carried out
with Gaussian 16, revision c.01,89 using the M06-L67,90 and M06-2X
functionals.66 The basis sets used for the initial geometry optimization
and frequency calculations on the ruthenium species included def2-
QZVP (with def2 ECP) for Ru, and def2-TZVP for all other atoms
(together with the W06 density fitting basis set).91,92 Subsequently, all
geometries were reoptimized using the def2-QZVP basis set for all
atoms. The polarizable continuum model (asymmetric isotropic
IEFPCM) was used in all (except H2) geometry optimizations and
frequency calculations, with the radii and nonelectrostatic terms of
Truhlar and co-workers’ SMD solvation model (scrf = smd).93 An
example of a typical g16 input file is provided in the Supporting
Information. The reported energies of the ruthenium species were
obtained by combining the electronic energies of the structures
optimized at the M06-L/def2-QZVP level with the thermal corrections
from the frequency calculations, plus the standard state correction94,95
Crystallographic data for 5, 6, and 7 (CIF)
File structures.xyz containing Cartesian coordinates of the
metal complexes computed in this study, where this file
may be opened as a text file to read the coordinates or
opened directly by a molecular modeling program such as
aspx) for visualization and analysis (XYZ)
AUTHOR INFORMATION
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Corresponding Authors
Eugene Khaskin − Okinawa Institute of Science and
Dmitry G. Gusev − Department of Chemistry and Biochemistry,
Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada;
Authors
Louise N. Dawe − Department of Chemistry and Biochemistry,
Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada;
Morteza Karimzadeh-Younjali − Department of Chemistry
and Biochemistry, Wilfrid Laurier University, Waterloo, ON
N2L 3C5, Canada
Zengjin Dai − Department of Chemistry and Biochemistry,
Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada
Complete contact information is available at:
Funding
Natural Sciences and Engineering Research Council (NSERC)
of Canada, Discovery grant program, and Compute Canada.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
D.G.G. is thankful to the NSERC of CanadaDiscovery grant
program, CFI LOF program, Compute Canada, and Wilfrid
Laurier University for support. Dr. Paul D. Boyle, the University
of Western Ontario, is acknowledged for assistance with the X-
ray data collection.
J
J. Am. Chem. Soc. XXXX, XXX, XXX−XXX