ACS Catalysis
EXPERIMENTAL SECTION
Research Article
Stoichiometric Reaction of [Pd(dba)(phen)] (7) with
Cu(OAc) ·H O (2a·H O). Complex 7 (41.9 mg, 0.0804
mmol), 2a·H O (32.16 mg, 0.1600 mmol), and a stirrer bar
■
2
2
2
General Procedures. All procedures described in this
paper were carried out in air, unless stated otherwise.
2
were placed in a Schlenk tube (25 mL) under a N2
atmosphere. Dry benzene (5.4 mL) was introduced into the
tube using a hypodermic syringe. The reaction mixture was
warmed at 60 °C for 3 h. A change of color from dark brown to
yellow or amber was noted. After cooling to room temperature,
the insoluble materials were removed by centrifugation. The
residue was washed with benzene (5 × 5 mL) and extracted
with dichloromethane (DCM, 5 mL) using ultrasonic
irradiation. The subsequent centrifugation gave a yellow
solution. The extraction process was repeated 7 times. The
combined yellow solution was filtered through a cannula with a
glass filter. All volatile solvents and compounds were removed
using a rotary evaporator, and the resulting solid was dried
Cu(OAc) ·H O (2a·H O), Cu(OAc) (2c), Cu O, CuO,
2
2
2
2
Cu(OPiv) , Cu(OTf) , Cu(OH) , Cu(acac) , Cu(HFacac) ,
2
2
2
2
2
CuCN, CuSCN, CuTC, CuCl , CuBr , CuCl, CuBr, and CuI
2
2
were purchased from commercial suppliers and used as
3
3
34
received. [Pd(OAc) (phen)], [Pd(dba) ], [Pd(dba)-
2
2
2
2
35
(
phen)], and [Cu(OAc) (phen)]·0.5H O (2b·0.5H O)
2 2 2
1
were prepared according to literature methods. H and
C{ H} nuclear magnetic resonance (NMR) spectra were
1
3
1
1
recorded on a JEOL ECX-400P instrument (400 MHz for H).
Chemical shifts (δ) are given in ppm, relative to
tetramethylsilane. All coupling constants are given in Hz.
Infrared spectra were recorded on a JASCO FT/IR-4100
instrument with the use of KBr disks. GLC analyses were
performed on a Shimadzu GC-14B instrument with an FID
detector equipped with an InertCap 1 column (0.25 mm i.d. ×
under vacuum. The obtained yellow powder was confirmed as
1
[
Pd(OAc) (phen)] (1b) by H NMR spectroscopy. Yellow
2
microcrystals, 31.0 mg (0.0767 mmol), 95% yield. The 2nd
trial of this process conducted under the same conditions also
gave 1b in 88% yield. A similar treatment of 6 (65.8 mg, 0.126
3
0 m). The catalytic reactions were carried out using an
EYELA SynFlex aluminum brock heater.
Solution-Phase XAFS Measurements. Cu K-edge
XANES and EXAFS measurements were carried out at the
BL01B1 beamline at SPring-8 of the Japan Synchrotron
Radiation Research Institute (JASRI). All measurements were
performed at room temperature. The Cu K-edge XAFS data
were recorded in the fluorescent mode. The X-ray energy was
calibrated using a Cu foil, and the data analyses were
performed utilizing ATHENA in the Demeter software
package for Windows (ver. 0.9.26). For the solution-phase
XAFS, the catalyst solution in dimethyl phthalate (3)
employed as the solvent was filtered through a PTFE
membrane filter of 0.2 μm pore size, and a portion of the
resulting solution (ca. 1 mL) was sealed in a plastic bag
mmol) with 2a·H O (25.20 mg, 0.1262 mmol) gave 1b in 56%
2
yield. Finally, the 2nd trial of the reaction of 7 with 2a·H O in
2
a 1/1 ratio gave 1b in 63% yield.
Stoichiometric Reaction of Cu(OAc) (2c) with AcOH.
c (150.07 mg, 1.2242 mmol), AcOH (7 mL), and a magnetic
2
stirrer bar were placed in an eggplant flask. Subsequently, a
reflux condenser was installed on the flask. The reaction system
was heated at 135 °C for 1.5 h under magnetic stirring. The
hot solution was filtered using a cannula with a glass filter. The
solution was allowed to cool at room temperature and the
deposition of deep blue cubic crystals was noted. The cubic
crystals were washed with hexane (3 × 5 mL). Further crystals
were obtained from the mother liquors and were treated
analogously. The combined crystals of 2a·AcOH were dried
under reduced pressure. The total yield of 2a·AcOH was
determined at 90% (265.2 mg, 1.09 mmol). This compound
was identified as 7 by single-crystal X-ray structure analysis.
Single-Crystal X-ray Structure Analysis. Single crystals
of 7 were selected using a polarized optical microscope. A
selected single-crystal suitable for single-crystal X-ray structure
analysis was mounted on top of a glass capillary using Paratone
N oil. A Rigaku AFC-7R Mercury II diffractometer with
graphite-monochromated Mo Kα radiation (λ = 0.71075 Å)
was used for data collection at 293 K. The collected data were
17
(
Seinichi Unipack S-4: 55 mm × 40 mm × 0.04 mm). The
sealed plastic bag was secured in a plastic slide mount (Hosho
slide mount, outside size: 50 mm × 50 mm, window size: 34
mm × 23 mm) for XAFS study.
XAFS Study of Cu Complexes in Dimethyl Phthalate.
2
a·H O (37.4 mg, 0.187 mmol), 3 (25 mL), and a magnetic
2
stirrer bar were placed in a 50 mL vial. The reaction system
was heated at 120 °C until its color changed to brown. The
solution (1 mL) was filtered through a PTFE membrane, and
the filtrate was transferred to a plastic bag before carrying out
the XAFS measurements.
XAFS Study of the Catalytic Solution. The catalytic
solution for the XAFS study was prepared and performed as
summarized in Table 1.
36
solved by direct methods (SHELXL ver. 2018/1) and refined
by a full-matrix least-squares procedure employing the Crystal
37
Structure program (ver. 4.3). All hydrogen atoms were
Catalytic Dehydrogenative Coupling of Dimethyl
treated as a riding model. The POV-Ray program (ver. 3.6.2)
Phthalate. [Pd(OAc) (phen)] (1a; 40.47 mg, 0.1000
38
2
was used for depiction of the molecules. CCDC 1963800
mmol), Cu(OAc) ·H O (2a·H O; 5.98 mg, 0.0300 mmol),
2
2
2
contains the supplementary crystallographic data for 2a·AcOH.
dimethyl phthalate (3; 25.0 mL, 150.0 mmol), and a magnetic
stirrer bar were placed in a four-necked round-bottom flask.
Subsequently, a reflux condenser, the gas inlet, a thermometer,
and a stopper were installed on the flask. A stream of air was
passed through the solution by means of a mini-compressor,
and the reaction system was heated at 200 °C for 6 h with
magnetic stirring at a rate of 820 rpm. A portion of the solution
ASSOCIATED CONTENT
■
(
500 μL) was transferred using a hypodermic syringe to a vial.
*
sı Supporting Information
Triphenylmethane as an internal standard (approx. 1 mmol)
and THF (170 μL) were added to the vial. The product yield
and conversion were estimated by GLC analysis.
5
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ACS Catal. 2020, 10, 5909−5919