S
-
1
SUPPORTING INFORMATION
Electrocatalytic Reduction of C
–
C π
-
bonds
via
a Cobaltocene
-
Derived C
oncerted
P
roton
-
E
lectron
T
ransfer
Mediator: Fumarate
Hydroge
n
ation as a Model Study
Joseph Derosa
†
,
Pablo Garrido
-
Barros
†
,
and
Jonas C. Peters
*
*
jpeters
@
caltech
.edu
Division of Chemistry and Chemical Engineering, California Institute of Technology (Caltech),
Pasadena, California 91125, United States
Table of Contents
S
-
2
S1. General Experimental Information
S
-
2
S1.1 Chemical/Reagent Considerations
S
-
2
S1.2 NMR Spectroscopy
S
-
2
S1.3 Electrochemistry
S
-
3
S2. Synthetic Details
S
-
3
S2.1 Fumarate Ester Synthesis
S
-
5
S2.
2 NMR Spectra
S
-
11
S3. Controlled Potential Coulometry (CPC)
S
-
11
S3.1
eCPET Reduction of Fumarate Esters using
[(Cp)Co(Cp
NMe
2
)][OTf]
S
-
1
4
S3.2
NMR Spectra
S
-
1
6
S3.3
Control Reaction with Cp
2
Co instead of [(Cp)Co(Cp
NMe
2
)][OTf]
S
-
1
7
S4. Kinetic Analysis
S
-
1
7
S4.1
General Introduction
S
-
1
7
S4.2
Kinetic Analysis of CPET by [(Cp)Co(Cp
N
Me
2
H
)]
+
S
-
2
1
S4.3
Error analysis
S
-
2
2
S4.4
Calculation of the rate of protonation
S
-
2
3
S
5
.
Cyclic Voltammetry
S
-
3
4
S
6
. Computational Details
S
-
5
4
S
7
. References
S
-
2
S1. General Experimental Information
S1.1 Chemical/Reagent Considerations:
Unless otherwise noted, a
ll materials were used as received from commercial sources without
further purification.
Fumaryl chloride,
phenol, cyclohexanol
,
4
-
trifluoromethylphenol, 4
-
chlorophenol, 4
-
fluorophenol, 4
-
methoxyphenol, 4
-
cyanoaniline, and tetrabutylammonium
hexafluorophosphate
were
used as
purchased from Aldrich, Alfa Aesar, Oakwood, and Combi
-
Blocks.
N,
N
-
dimethylaniline
-
4
-
cobaltocenium triflate [
CpCoCp
NMe
2
][OTf],
1
anilinium triflate
acids,
2
deuterosubstituted 4
-
cyanoaniline (
4
-
CN
PhND
2
),
3
w
ere
synthesized according to
previously reported procedure
s
.
Teflon
-
coated magnetic stir bars were soaked in concentrated
nitric acid for at least 1 h, washed repeatedly with deionized water then acetone, and dried in an
oven prior to use.
In air
-
or moisture
-
sensitive reactions,
solvents were deoxygenated and dried
by thoroughly sparging with N
2
followed by passage through
an activated alumina column in a
solvent purification system by SG Water, USA LLC. Non
-
halogenated solvents were tested with
sodium benzophenone ketyl in tetrahydrofuran (THF) in order to confirm the absence of oxygen
and water. Deuterated solvents were pu
rchased from Cambridge Isotope Laboratories, Inc.,
degassed, and dried over activated 3
-
Å molecular sieves prior to use
.
S1.2 NMR Spectroscopy:
1
H,
13
C, and
19
F spectra were recorded with
Varian
400
MHz and
Bruker
500
MHz
spectrometers
. Spectra were
internally referenced to SiMe
4
or solvent signals. The following
abbreviations (or combinations thereof) were used to explain multiplicities: b = broad, s =
singlet, d = doublet, t = triplet, q = quartet, p = pentet, sept = septet, and m = multiplet.
S1.
3 Electrochemistry:
A CHI instruments 600B electrochemical analyzer was used for all electrochemical data
collection. Cyclic voltammetry (CV), linear sweep voltammetry (LSV) and differential pulse
voltammetry (DPV) experiments were carried out in a one
-
co
mpartment three
-
electrode cell
using a boron doped diamond (BDD) disk as the working electrode (3 mm diameter), a Pt wire as
the counter electrode, and a Ag/AgOTf (5 mM) reference electrode. Details for the CVs and
LSVs are noted as they appear. DPVs were
obtained with the following parameters: amplitude
=
50 mV, step height
=4 mV, pulse width
= 0.05 s, pulse period
= 0.5 s and sampling width=
0.0167 s. E
1/2
values for the reversible waves were obtained from the half potential between the
oxidative and redu
ctive peaks and for irreversible processes are estimated acc
ording to the
potential at the i
max
in DPV measurements. For all measurements IR compensation was applied
accounting for 85% of the total resistance. All of the reported potentials are referenced
to the
ferrocenium/ferrocene couple (Fc+/0).
S
-
3
S
2
.
Synthetic Details
S2.1 Fumarate Ester Synthesis:
Figure
S1.
Synthesis of
fumarate esters using fumaryl chloride and alcohols.
General Procedure for
Fumarate Ester Synthesis
:
To a
100
-
mL
round
-
bottomed
flask
equipped with a Teflon
-
coated stir bar
w
as
added
a solution of triethylamine (10 mmol, 2 equiv,
1.39
mL)
and
fumaryl chloride (5 mmol, 1 equiv, 0.546 mL) in
anhydrous dichloromethane (1
5
mL)
and cooled to 0
º
C
.
While stirring, a solut
ion of appropriate alcohol
(5
mmol, 1 equiv)
in
anhydrous
dichloromethane
(
5
mL)
was added dropwise
.
The reaction mixture was allowed to
stir at
0
º
C and naturally warm to room temperature over 12 h
. The reaction mixture was then
washed with
1M
HCl
solution
(60 mL) and extracted with DCM (4
×
50 mL). The organic layers
were combined
,
and
the solvent was
removed
in vacuo
to yield
corresponding powders or oils
.
Purification
by washing solid residue with ethyl acetate or
column chromatography gave the p
ure
product.
diphenyl fumarate
(1a
):
The title compound was prepared fr
om
phenol
(10 mmol, 2 equiv, 940 mg),
according to the general
fumarate ester
synthesis
procedure.
Purification by washing dark brown residue with
ethyl acetate and filtering
gave th
e pure product as a white solid
(
9
9
2
mg
,
74
% yield).
1
H NMR
(
4
00 MHz, CDCl
3
)
δ 7.43 (t,
J
= 7.9 Hz, 4H), 7.29 (t,
J
= 7.5 Hz, 2H),
7.25 (s, 2H), 7.18 (d,
J
= 8.0 Hz, 4H)
;
13
C NMR
(1
0
0 MHz, CDCl
3
)
δ 161.94, 150.39, 134.19,
130.59, 126.91, 121.40.
MS
(ESI) mass calculated for C
16
H
13
O
4
+
[M+H
]
+
269.1, found 269.1.
The
characterization data is in agreement with previous reports.
4
bis(4
-
(trifluoromethyl)phenyl) fumarate
(1
b
):
The title
compound was prepared fro
m
4
-
trifluoromethylphenol (10
mmol, 2 equiv,
1.62
g),
according to the general
fumarate ester
synthesis
procedure. Purification using silica gel column
chromatography (
92
:
4:
4 hexanes:EtOAc:DCM
) gave the pure product as a white solid
(1.21
g,
61
% yield).
1
H NMR
(
4
00 MHz, CDCl
3
)
δ 7.71 (d,
J
= 8.5 Hz, 4H), 7.32 (d,
J
= 8.5 Hz, 4H),
7.27 (s, 2H)
;
13
C NMR
(1
0
0 MHz, CDCl
3
)
δ 162.56, 152.72, 134.62, 128.91 (q,
J
C
–
F
= 33.0 Hz),
127.18 (q,
J
C
F
= 3.7 Hz), 125.22 (q,
J
C
–
F
= 271.0 Hz), 121.95
;
19
F NMR
(400 MHz, CDCl
3
) δ
-
62.35.
MS
(ESI) mass calculated for C
1
8
H
1
1
F
6
O
4
+
[M+H
]
+
405.1, found 405.1.
bis(4
-
(
chloro
)phenyl) fumarate
(1
c
):
The title compound was
prepared fro
m
4
-
chloro
phenol (10 mmol, 2 equiv,
1.28
g),
according
to the general fumarate ester synthesis procedure.
Purification by washing dark brown residue with ethyl acetate and
R
OH
Cl
O
Cl
O
+
O
O
O
O
R
R
2 equiv NEt
3
DCM, 0
º
C to rt, 12h
2 equiv
O
O
O
O
1a
O
O
O
O
1b
CF
3
F
3
C
O
O
O
O
1c
Cl
Cl
S
-
4
filtering
gave the pure product as a white solid (
1.43
g,
85
% yield)
.
1
H NMR
(400 MHz, CDCl
3
)
δ 7.39 (d,
J
= 8.9 Hz, 4H), 7.22 (s, 2H), 7.1
3 (d,
J
= 8.8 Hz, 4H)
;
13
C NMR
(100 MHz, CDCl
3
)
δ
162.58, 148.39, 134.20, 131.65, 131.10, 127.75, 122.42
.
MS
(ESI) mass calculated for
C
1
6
H
1
1
Cl
6
O
4
+
[M+H
]
+
337.0, found 337.0.
bis(4
-
(
methoxy
)phenyl) fumarate
(1
d
):
The title compound
was prepared
from 4
-
methoxy
phenol (10 mmol, 2 equiv,
1.36
g), according to the general fumarate ester synthesis procedure.
Purification using silica gel column chromatography (
70:15:15
hexanes:EtOAc:DCM
) gave the pure product as an off
-
w
hite solid (
853
mg,
52
% yield).
1
H
NMR
(400 MHz, CDCl
3
)
δ 7.21 (s, 1H), 7.09 (d,
J
= 9.1 Hz, 2H), 6.93 (d,
J
= 9.1 Hz, 2H), 3.62
(s, 6H)
;
13
C NMR
(100 MHz, CDCl
3
)
δ 163.70, 158.17, 144.54, 135.87, 123.81, 114.70, 55.75.
MS
(ESI) mass calculated for C
1
8
H
1
7
O
6
+
[M+H
]
+
329.1, found 329.1.
di
cyclohexyl
fumarate
(1
e
):
The title compound was prepared fro
m
cy
clo
hexanol (10 mmol, 2 equiv,
1.3
m
L
), according to the general
fumarate ester synthesis procedure. Purification using silica gel column
chromatography (9
6
:
4
hexanes:EtOAc) gave the pure product as a
colorless oil (
1.03
g,
69
% yield).
1
H NMR
(400 MHz, CDCl
3
)
δ 6.82 (s, 2H), 4.86 (tt,
J
= 8.9,
4.0 Hz, 2H), 1.87 (dd,
J
= 9.8, 4.6 Hz, 4H), 1.79
–
1.70 (m, 4H), 1.61
–
1.27 (m, 12H)
;
13
C NMR
(100 MHz, CDCl
3
)
δ 234.50, 164.67, 134.06, 73.38, 31.61, 25.43, 23.76
.
MS
(ESI) mass
calculated for C
1
6
H
25
O
4
+
[M+H
]
+
281.2, found 281.2. The characterization data is in agreement
with prev
ious reports.
5
O
O
O
O
1d
OMe
MeO
O
O
O
O
1e
S
-
5
S2.2 NMR Spectra
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