Organometallics
Article
cannula into a clean Schlenk tube. The solvent was removed under
vacuum, and the resulting solid was washed with diethyl ether (3 × 5
mL) and then dried overnight under vacuum to give 0.046 g (yield:
resulting solid was washed with cooled water (1 mL) and dried
overnight under vacuum to give 0.060 g (yield 74%) of the desired
product, obtained as a yellow solid. 1H NMR (400 Hz, D2O): δ 8.46−
8.45 (m, 2H, CH), 8.04−8.00 (m, 2H, CH), 7.42 (d,3JH−H = 8.4 Hz,
2H, CH), 7.36−7.33 (m, 2H, CH), 1.48 (s, 15H, Cp* CH3). 13C{1H}
NMR (100 MHz, D2O): δ 151.0, 150.5, 141.9, 121.5, 115.2, 88.2, 7.7.
19F NMR (376.44 MHz, D2O): δ −72.09 (d, JF−P = 708 Hz). 31P
NMR (161.99 MHz, D2O): δ −145.05 (sept, JP−F = 708 Hz). HRMS
(ESI, H2O): m/z calculated for C20H24N3Ir, 249.5794; m/z measured,
249.5791.
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92%) of the desired product as a yellow solid. H NMR (400 Hz,
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D2O): δ 8.71 (d, JH−H = 5.6 Hz, 2H, CH), 8.02−7.98 (m, 2H, CH),
7.33−7.29 (m, 4H, CH), 5.89 (d, 3JH−H = 8.4 Hz, 2H, p-cymene CH),
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5.80 (d, JH−H = 8.4 Hz, 2H, p-cymene CH), 2.54 (hept, JH−H = 6.8
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Hz,1H, iPr CH), 2.10 (s, 3H, CH3), 1.18 (d, JH−H = 6.8 Hz, 6H, iPr
CH3). 13C{1H} NMR (100 MHz, D2O): δ 152.6, 152.3, 141.4, 120.0,
114.9, 104.5, 100.2, 84.2, 83.7, 30.4, 21.1, 17.1. HRMS (ESI, H2O): m/
z calculated for C20H23N3O4NaSRu, 526.0350; m/z measured,
526.0349.
Synthesis of [(bdpa)Cp*Ir](PF6)2 (Ir2′). With the same procedure as
for the synthesis of Ir1′, Ir2′ was obtained as a yellow powder (yield:
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Synthesis of [(dpa)Cp*IrOSO3] (Ir1). [(dpa)Cp*IrCl]Cl (0.057 g,
0.1 mmol) was weighed into a 20 mL Schlenk tube and dissolved in 2
mL of water. Silver sulfate (0.031 g, 0.1 mmol) was added, and the
reaction mixture was stirred at 40 °C for 16 h. The suspension was
filtered into a clean Schlenk tube. The solvent was removed under
vacuum, and the resulting solid was washed with diethyl ether (3 × 5
mL) and dried overnight under vacuum to give 0.054 g (yield 91%) of
82%). H NMR (400 MHz, D2O): δ 8.61−8.59 (m, 2H, CH), 7.98−
7.94 (m, 2H), 7.53−7.37 (m, 9H, CH), 5.54 (s, 2H, CH2), 1.49 (s,
15H, Cp* CH3). 13C NMR (100 MHz, D2O): δ 153.9, 151.0, 142.3,
134.3, 129.0, 128.0, 126.6, 122.5, 116.8, 88.3, 56.3, 7.7. 19F NMR
(376.44 MHz, D2O): δ −72.12 (d, JF−P = 708 Hz). 31P NMR (161.99
MHz, D2O): δ −145.07 (sept, JP−F = 708 Hz). HRMS (ESI, H2O): m/
z calculated for C27H30N3Ir2+, 294.6029; m/z measured, 294.6032; [M
+ H2O − H]+ m/z calculated for C20H25N3OIr+, 606.2091; m/z
measured, 606.2082.
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the product as a yellow solid. H NMR (400 Hz, D2O): δ 8.46 (d,
3JH−H = 5.6 Hz, 2H, CH), 8.02 (m, 2H, CH), 7.43 (d, 3JH−H = 8.4 Hz,
2H, CH), 7.34 (m, 2H, CH), 1.47 (s, 15H, Cp* CH3). 13C{1H} NMR
(100 MHz, D2O): δ 151.0, 150.4, 141.9, 121.4, 115.2, 88.1, 7.7. HRMS
(ESI, H2O): dicationic compound detected as the major product m/z
(z = 2) calculated for C20H24N3Ir, 249.5794; m/z measured, 249.5797
Synthesis of (bdpa)Cp*IrO4S (Ir2). With the same procedure as for
the synthesis of Ir1, Ir2 was obtained as a yellow powder (yield: 91%).
1H NMR (400 MHz, D2O): δ 8.61−8.60 (m, 2H, CH), 7.98−7.93 (m,
2H), 7.53−7.37 (m, 9H, CH), 5.54 (s, 2H, CH2), 1.49 (s, 15H, Cp*
CH3). 13C NMR (100 MHz, D2O) δ 153.8, 151.0, 142.3, 134.2, 129.0,
128.0, 126.6, 122.5, 116.8, 88.3, 56.2, 7.6. HRMS (ESI, H2O): m/z
calculated for C27H30N3O4NaSIr, 708.1484; m/z measured, 708.1481.
Synthesis of [Cp*Ir(bpy)OSO3] (Ir3). [Cp*IrCl2]2 (0.079 g, 0.1
mmol) and silver sulfate (0.062 g, 0.2 mmol) were added in water (2
mL), and the reaction mixture was stirred at room temperature for 16
h. The suspension was filtered by cannula into a clean Schlenk tube,
and bipyridine (0.031 g, 0.2 mmol) was added. The mixture was
stirred at 40 °C for 16 h. Then the solvent was removed under vacuum
and the resulting solid was washed with diethyl ether (3 × 5 mL) and
then dried overnight under vacuum to give 0.043 g (yield 74%) of the
desired product obtained as a yellow solid. 1H NMR (400 Hz, D2O): δ
9.15 (d, 3JH−H = 5.2 Hz, 2H, CH), 8.57 (d, 3JH−H = 8.4 Hz, 2H, CH),
Synthesis of [(dpa)Cp*IrH](PF6) (Ir5). A solution of Ir1 (0.018 g,
0.03 mmol) and HCOONa (0.816 g, 12 mmol) in degassed H2O (2
mL) was heated at 70 °C for 30 min. KPF6 (0.056 g, 0.03 mmol) was
then added to the mixture, and the reaction mixture was stirred at
room temperature for 0.5 h. The solid was filtered and washed with
degassed water to give a light yellow powder after drying under
vacuum (0.014 g, 75%). 1H NMR (400 MHz, DMSO): δ 8.52 (s, 1H,
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NH), 8.31 (d, JH−H = 5.6 Hz, 2H, CH), 7.83−7.79 (m, 2H, CH),
7.36−7.27 (m, 2H, CH), 6.91−6.86 (m, 2H, CH), 1.55 (s, 15H, Cp*
CH3), −9.44 (s, 1H, Ir−H). 13C NMR (100 MHz, DMSO) δ 154.9,
153.2, 139.9, 119.6, 114.5, 87.8, 9.1. 19F NMR (376.44 MHz, DMSO):
δ −70.16 (d, JF−P = 711 Hz). 31P NMR (161.99 MHz, DMSO): δ
−144.19 (sept, JP−F = 711 Hz). HRMS (ESI, H2O): dicationic
compound detected as the major product m/z (z = 2) calculated for
C20H24N3Ir, 249.5794; m/z measured, 249.5797.
General Experimental Procedure for Transfer Hydrogena-
tion of Levulinic Acid. Safety: As these reactions generate pressures
up to 5 bar, they were carried out in heavy-walled (2.7 mm) Schlenk
tubes of small size (h = 11 cm, o.d. = 2 cm) equipped with a Teflon
rotaflow manifold. A mobile polycarbonate safety shield was also
installed as protection equipment.
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8.36 (dd, JH−H = 8.0 Hz, 2H, CH), 7.92 (dd, JH−H = 6.0 Hz, 2H,
CH), 1.69 (s, 15H, Cp* CH3). 13C{1H} NMR (100 MHz, D2O): δ
156.0, 151.6, 141.6, 129.3, 124.3, 89.3, 7.7. HRMS (ESI, H2O): m/z
calculated for C20H23N2Ir2+, 242.0739; m/z measured, 247.0742.
Synthesis of [(dpa)(p-cymene)Ru](PF6)2 (Ru1′). [(dpa)(p-
cymene)RuOSO3] (0.050 g, 0.1 mmol) was weighed into a 20 mL
Schlenk tube and dissolved in 2 mL of water. Potassium
hexafluorophosphate (0.040 g, 0.22 mmol, 2.2 equiv) was added,
and the reaction mixture was stirred at room temperature for 30 min.
The suspension was filtered by cannula. The resulting solid was
washed with cooled water (1 mL) and then dried overnight under
vacuum to give 0.051 g (yield: 71%) of the desired product obtained as
LA (2 mmol), FA (2−4 mmol), and catalyst (0.0005−0.1 mol %),
with or without water (0−6 mL), were placed in a 15 mL Schlenk tube
with a Teflon screw cap. The mixture of substrates and catalyst was
heated to the desired temperature in less than 15 min. After the
reaction, the crude mixtures were analyzed by 1H NMR. Volatile
compounds were removed under vacuum, and the crude product was
purified by column chromatography using petroleum ether/ethyl
acetate (3/1; v/v) as eluent.
General Experimental Procedure for Hydrogenation of
Levulinic Acid. Catalyst (0.0005−0.1 mol %), levulinic acid (2
mmol), and water (0.5−4 mL) were placed in a 20 mL high-pressure
Parr reactor. Low catalyst loadings requiring less than 1 mg of catalyst
(loading <0.1 mol %) were realized by dilution of the catalyst in water.
The reactor was flushed with H2 and then pressurized with stirring
with the mentioned hydrogen pressure. Once the pressure was
reached, the reactor was maintained connected for an additional 2 min
before closing. The mixture was stirred at the appropriate temperature
for the desired time. After the reaction, the reactor was cooled in an ice
bath and carefully depressurized. The product mixture was analyzed by
1H NMR. The crude product was purified by column chromatography
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a brown solid. H NMR (400 Hz, D2O): δ 8.70 (d, JH−H = 5.6 Hz,
2H, CH), 8.02−7.98 (m, 2H, CH), 7.33−7.28 (m, 4H, CH), 5.88 (d,
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3JH−H = 6.4 Hz, 2H, p-cymene CH), 5.79 (d, JH−H = 6.0 Hz, 2H, p-
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cymene CH), 2.54 (hept, JH−H = 6.8 Hz, 1H, iPr CH), 2.10 (s, 3H,
3
CH3), 1.18 (d, JH−H = 7.2 Hz, 6H, iPr CH3). 13C{1H} NMR (100
MHz, D2O): δ 152.6, 152.3, 141.4, 120.0, 114.9, 104.5, 100.2, 84.2,
83.8, 30.4, 21.1, 17.1. 19F NMR (376.44 MHz, D2O): δ −72.08 (d, JF−P
= 708 Hz). 31P NMR (161.99 MHz, D2O): δ −145.06 (sept, JP−F
=
708 Hz). HRMS (ESI, H2O): m/z calculated for C20H23N3Ru2+,
203.5462; m/z measured, 203.5465; [M + H2O]2+ m/z calculated for
C20H25N3ORu2+, 212.5515; m/z measured, 212.5515.
using petroleum ether/ethyl acetate (3/1; v/v) as eluent.
Control experiments were performed by running reactions under
the aforementioned conditions without any catalyst.
Synthesis of [(dpa)Cp*Ir](PF6)2 (Ir1′). (dpa)Cp*IrO4S (0.059 g, 0.1
mmol) was weighed into a 20 mL Schlenk tube and dissolved in 2 mL
of water. Potassium hexafluorophosphate (0.040 g, 0.22 mmol, 2.2
equiv) was added, and the reaction mixture was stirred at room
temperature for 30 min. The suspension was filtered by cannula. The
Dehydration of Carbohydrate Biomass and Subsequent
Hydrogenation. Glucose or fructose (0.45 g, 2.5 mmol) was loaded
into a 20 mL autoclave, and H2SO4 (2.5 mL, 0.5 mol/L) was then
added. The autoclave was quickly heated to 180 °C, and the contents
were vigorously stirred for 2 h. After the reaction, the insoluble solid
I
Organometallics XXXX, XXX, XXX−XXX