S
1
A Carborane
-
derived Proton
-
Coupled Electron Transfer Reagent
Enric H. Adillon and Jonas C. Peters
*
Division of Chemistry and Chemical Engineering, California Institute of Technology
(Caltech)
,
Pasadena,
California 91125, United States
*E
-
mail:
jpeters@caltech.edu
CONTENTS
S1. EXPERIMENTAL PART
................................
................................
................................
........
1
S2. SYNTHETIC PROCEDURES
................................
................................
................................
.
3
S3. NMR SPECTRA
................................
................................
................................
.......................
6
S4. EPR SPECTRA
................................
................................
................................
......................
24
S5. UV
-
VIS SPECTRA
................................
................................
................................
................
27
S6. X
-
RAY CRYSTALLOGRAPHY
................................
................................
...........................
32
S7. ELECTROCHEMISTRY
................................
................................
................................
.......
35
S8. pK
a
DETERMINATION
................................
................................
................................
........
37
S9. KINETIC ANALYSIS OF AZOARENE REDUCTION
................................
.......................
40
S10. KINETIC ANALYSIS OF HYDROGEN EVOLUTION
................................
....................
45
S11. GC CALIBRATION CURVES AND CHROMATOGRAMS
................................
............
50
S12. COMPUTATIONAL DETAILS
................................
................................
..........................
52
S13. REFERENCES
................................
................................
................................
.....................
55
S1. EXPERIMENTAL
PART
1.1
General Considerations
All manipulations were carried out using standard Schlenk or glovebox techniques under an N
2
a
tmosphere
unless state
d
otherwise
.
Solvents
were
degassed
by thoroughly
sparging with N
2
gas
and dried
by passage through an activated alumina column in the solvent
purification
system by
SG Water, USA LLC.
All solvents were stored over activated 3
Å
sieves prior to use.
THF, 2
-
MeTHF, and diethyl ether were dried over NaK alloy and passed over activated alumina prior to
use
and
were
checked
with a
standard
solution
of sodium benzophenone ketyl in tetrahydrofuran
to
test for
the presence of
oxygen and
moisture.
All reagents were purchased from commercial
vendors and used
without further purification unless otherwise stated.
Decaborane
bis(acetonitrile),
1
diphenyl
-
o
-
carborane,
1
N,N
-
dimethyl
-
4
-
(phenyl
ethynylaniline),
2
1
-
(4
-
N,N
-
dimethylaniline)
-
2
-
phenyl
-
o
-
carborane,
3
1,2
-
di
-
p
-
tolyldiazene,
4
1,2
-
bis
-
(4
-
bromo)diazene
,
4
1,2
-
S
2
bis
-
(4
-
chloro
)diazene,
4
1,2
-
bis
-
(4
-
chloro)diazene,
4
1,2
-
bis
-
(4
-
methoxy)diazene,
4
diethyl
4,4’
-
(diazene
-
1,2
-
diyl)
-
dibenzoate,
4
diphenylfumarate,
5
4
-
cyanoanilinium triflate,
6
and
2
-
chloroanilinium triflate
,
6
and triphenylphosphonium triflate
7
were prepared by reported methods.
n
Bu
4
NPF
6
was recrystallized from hot EtOH three times and dried under vacuum at 100
°C
overnight.
High resolution mass spectra (HRMS) were obtained from the Caltech Mass Spectral
Facility using JEOL JMS
-
T2000GC AccuTOF
TM
GC
-
Alpha High Resolution Mass Spectrometer
in field desorption (FD+) mode.
1.2
NMR
Spectroscopy
NMR spectroscop
y
was performed using Varian and Bruker 400 MHz NMR spectrometers fitted
with broadband auto
-
tune probes.
Deuterated solvents were purchased from Cambridge Isotope
Laboratories, Inc.
.
Acetonitrile
-
d
3
was
d
egassed
by three freeze
-
pump
-
thaw cycles
,
dried over
activated 3
Å
sieves
,
and passed over activated alumina
.
1
H
and
13
C chemical shifts are reported
in ppm relative to tetramethylsilane using
residual solvent resonances as internal standards.
11
B
chemical shifts are reported in ppm relative to
boron triflu
oride etherate
using absolute referencing
to a
1
H NMR spectrum collected concurrently.
19
F chemical shifts are reported in ppm relative to
trichlorofluoromethane using absolute referencing to a
13
C NMR spectrum collected concurrently.
1.3 Products Quantification
GC
-
FID analyses were performed using an Agilent 6890N
G
as
C
hromatograph.
Substrate
reductions were pumped down to remove solvent and redissolved in either chloroform
-
d
1
(600 uL)
for
NMR analysis
or ethyl acetate (2 mL)
for GC
-
FID analysis. For
quantitative NMR
analyses
,
dibromomethane
(5 mmol, 1 eq) was
added as
an internal standard.
For
GC
-
FID
analysis
,
a
dodecane
solution in ethyl acetate
(5
0 uL
,
200 mM
) was
added as an internal standard
, and
analyte
response factors
were
measured
via
calibration curves
with known analyte
concentrations.
GC
-
TCD analysis was performed in the Caltech Environmental Analysis Center using a Hewlett
Packard 5890 Series II Gas Chromatograph. A calibration curve was generated by direct injection
of known quantities of
hydrogen gas
.
A
liquot of the headspace
(100 uL)
w
ere
analyzed in triplicate
and reported as an average.
1.
4
CW EPR Spectroscopy
77 K X
-
Band EPR spectra were collected on a Bruker EMX spectrometer. Solutions were prepared
as frozen glasses in NaK alloy dried 2
-
MeTHF filtered over activated alumina. Spectra were
simulated using the Easy Spin simulation toolbox (release 5.2.35).
8
1.
5
UV
-
v
is Spectroscopy
Spectra were collected using a Cary 60 instrument with Cary WinUV software. Time
-
course
spectra were collected with the Scanning Kinetics application of the Cary WinUV software. 1
-
cm
path quartz cells were pre
-
cooled in a Unisoku cryostat prior to analysis
. All spectra were
background corrected at the temperature at which spectra were collected.
1.
6
X
-
ray Crystallography
X
-
ray diffraction (XRD) studies were carried out at the Beckman Institute Crystallography
Facility
on a Bruker Kappa Apex II
diffractometer (
Cu
Kα radiation, λ =
1.5406 Å
). All crystals
were
mounted on a glass fiber loop under Paratone N oil. Structures were solved using SHELXS
or
SHELXT and refined against F2 on all data by full
-
matrix least squares with SHELXL.
9
All
of
the
S
3
solutions were performed in the Olex2 program.
10
H
ydrogen atoms were placed in
calculated
positions. Non
-
hydrogen atoms were refined anisotropically.
1.
7
Electrochemistry
Electrochemical measurements were carried out in an N
2
-
filled glovebox in a 20 mL scintillation
vial fitted with a septum cap containing punched
-
out holes for insertion of electrodes. A C
H
I
nstr
uments
6
00B
electrochemical analyzer was used for data collection.
For all experiments, a
boron
-
doped diamond
disk
electrode was used as the working electrode
; a f
reshly
polished
glassy
carbon
disk electrode was used as the counter electrode; a
silver wire immersed in a
solution of
silver triflate (
5 mM
) and
n
Bu
4
PF
6
(200 mM)
separated from the working solution by a
Vycor
frit
was used as
pseudoreference
electrode
.
E
1/2
values for reversible waves were determined as the
half potential between the peak oxidative and reductive potentials.
Solution resistance was
measured, and a correction of 85% of the uncompensated resis
tance was applied.
All reported
potentials
are referenced to the ferrocene
/ferrocenium
couple,
measured at the end of each
experiment. Electrochemistry solvents were passed over a pipet filter of
activated alumina
immediately before use.
1.
8
DFT
Calculations
All
calculations were performed using the ORCA 5
.0.3
program
using the B3LYP
functional with
the
def2
-
SVP
basis set
.
11
,
12
In cases where crystal structures were available,
those coordinates were
used as the input.
Geometry optimization calculations
were
performed
using the
SMD
solvation
model
with
acetonitrile.
13
Single
-
point v
ibrational frequency calculations were performed to
ensure that stationary points
were
absent of any imaginary frequencies and thus
were
local minima
on the potential energy surface.
Bond dissociation free energies
(BDFEs)
were calculated by an
established method using the
calculated
free energy of the H atom.
12
Reduction potentials were
determined by
a semi
-
empirical
method using the
calculated exchange reactions
relative to an
experimental reduction potential
. In the case of carboranes, the potential was calculated as an
exchange reaction with the
1,2
-
diphenyl
-
o
-
carborane anion using i
ts measure potential as a
reference
(E
1/2
=
-
1.56 V vs. Fc
0/+
).
In the case of diazenes, the potential was calculated as an
exchange reaction with the
azobenzene
anion was using its reported potential as a reference (E
1/2
=
-
1.82 V vs. Fc
0/+
).
Hydricities
were calculated
using
the BDFE and reduction potential methods
to yield a net hydride transfer free energy.
S2. SYNTHETIC PROCEDURES
[Diphenyl
-
o
-
carborane]
K
(18
-
crown
-
6)
(1)
P
otassium metal [33 mg, 0.85 mmol] was smeared onto the interior wall of a 20 mL scintillation
vial. D
iphenyl
-
o
-
carborane [
300 mg, 1.0 mmol] was dissolved in 15 mL of THF and added to the
potassium, quickly forming a red solution. The reaction was stirred until all potassium was
consumed, approximately three hours.
A solution of 18
-
crown
-
6 [
264 mg, 1.0 mmol
] in THF [~2
mL] was added dropwise.
The
solution
was filtered through celite, and the solvent was removed
under vacuum. The resulting
red
solid was wash
ed with pentane [3 x
5
mL] and dried under
vacuum, yielding
398
mg (
79
%) of a
red solid
.
The solid was recrystallized
by vapor diffusion of
pentane into a concentrated THF solution.
μ
eff
(CD
3
CN,
Evans method,
298 K):
1.
68
μ
B
.
S
4
[Diphenyl
-
o
-
carborane]
[
K
(18
-
crown
-
6)]
2
(2)
P
otassium metal [
12
mg, 0.
30
mmol] was smeared onto the interior wall of a 20 mL
scintillation
vial. Diphenyl
-
o
-
carborane [
35
mg,
0.12
mmol] was dissolved in
5
mL of THF and added to the
potassium, quickly forming a red solution
which
later became
light yellow
.
The reaction was
stirred until all potassium was consumed, approximately three hours. The solution was filtered
through celite, and
a solution of 18
-
crown
-
6 [63 mg] in THF [~2 mL] was added dropwise, yielding
a yellow precipitate. T
he
solvent
was removed under vacuum
. T
he resulting yellow
powder
was
washed with pentane [3 x 3 mL] and dried under vacuum, yielding
91
mg (
84
%) of a
pale
-
yellow
powder.
Diffraction quality crystals were grown by
layering
Et
2
O/MeCN and cooling at
-
35 °C.
1
H NMR (CD
3
CN, 400 MHz, 298 K)
δ 7.19 (d,
J
= 7.5 Hz, 1H), 6.87 (t,
J
= 7.5 Hz, 1H), 6.60 (t,
J
= 7.2 Hz, 1H)
, 0
-
3.2 (bm, 10H).
11
B{
1
H} NMR (CD
3
CN, 128 MHz, 298 K) δ: 7.81 (bs, 2B),
-
8.52 (bs, 2B),
-
17.68 (bs, 4B),
-
27.28 (bs, 2B).
13
C{
1
H} (CD
3
CN, 128 MHz, 298 K) δ:
157.66,
127.28, 127.12, 120.01, 70.84
.
[1
-
(4
-
N,N
-
dimethylaniline)
-
2
-
phenyl
-
o
-
carborane]K
(benzo
-
15
-
crown
-
5)
2
(3)
P
otassium metal [
110
mg,
2.8
mmol] was smeared onto the interior wall of a 20 mL scintillation
vial. 1
-
(4
-
N,N
-
dimethylaniline)
-
2
-
phenyl
-
o
-
carborane [
1.00
g,
2.95
mmol] was dissolved in
20
mL of THF and added to the potassium, quickly
changing from a colorless to
red solution. The
reaction was stirred until all potassium was consumed, approximately three hours. The solution
was filtered through celite, and the solvent was
reduced under
vacuum
to 10 mL
.
Benzo
-
15
-
crown
-
5 [1.52 g, 2.80 mmol] was added, forming a red precipitate.
The
remai
ning solvent was removed,
washed with pentane [3 x 3 mL] and recrystallized by THF/pentane vapor diffusion,
yielding
2.33
g (91%) of
a red
microcrystalline
solid
.
X
-
Ray diffraction
quality
crystals
acetonitrile/
diethyl ether
vapor diffusion
, yielding red needles.
μ
eff
(CD
3
CN, Evans method, 298 K):
1.
78
μ
B
.
[1
-
(4
-
N,N
,N
-
tri
methylanilin
ium
)
-
2
-
phenyl
-
o
-
carborane]
OTf
(4)
C
arborane
3
[25
0
mg, 0.
74
mmol] was dissolved in diethyl ether [
1
5 mL] in a 20 mL scintillation
vial and cooled in the cold well
chilled by
a dry ice
-
acetone bath. Methyl triflate [1
39
uL, 0.
89
mmol] was added, and
shortly after,
the vial was removed from the cold well and stirred for 18
hours
,
during which time a white precipitate formed
. The
white solid was filtered over a celite frit,
washed with diethyl ether [5 x 3 mL], and then dissolved in THF [5 mL].
The solvent of the THF
filtrate
was
removed under vacuum,
resulting
in 260 mg
(70%)
of a white
solid.
1
H NMR (CD
3
CN
,
400 MHz, 298
K
)
δ:
7.74 (
d, J = 9.3 Hz, 2H), 7.57 (d, J = 9.3 Hz, 2H),
7.53 (d, 7.4 Hz, 2H),
7.33
(
t
, J =
7.4
Hz,
1
H
), 7.23 (
dd, 8.3, 7.4 Hz
,
2H
), 3.40 (s, 9H)
, 3.37 (bs, 2H), 2.4
a
(bs, 6H), 2.33 (bs,
2H).
11
B{
1
H} NMR (CD
3
CN, 128 MHz, 298 K) δ:
-
3.55 (bs, 2B),
-
11.23 (m, 8B).
13
C{
1
H}
(CD
3
CN, 128 MHz, 298 K) δ:
149.04, 133.72, 133.56, 131.81, 131.66, 130.65, 129.64, 86.79,
84.01, 57.80.
19
F (CD
3
CN, 376 MHz, 298 K) δ:
-
79.4 (s,
3
F)
.
H
RMS
: (FD+) calculated for
C
17
H
28
B
10
N [M
+
]: 354.32278, found: 354.32284
.
1
-
(4
-
N,N
,N
-
tri
methylanilin
ium
)
-
2
-
phenyl
-
o
-
carborane
(5)
Carborane
4
[47 mg, 0.09 mmol] was dissolved in THF [5 mL] in a 20 mL scintillation vial and
cooled to
-
78 °C in the cold well. A freshly prepared solution of sodium napthalanide
[0.09 mmol]
was added dropwise to the carborane solution, forming a dark pink solution. The solution was
pumped down under vacuum, and the solid was washed with pentane [3 x 1 mL]. The solid was
redissolved in in THF, filtered,
layered with diethyl ether, and placed in the freezer overnight,
forming
15 mg (47%) of a
fine
pink
powder
.
μ
eff
(CD
3
CN,
Evans method
, 298 K):
1.
60
μ
B
.
S
5
General procedure for substrate reduction by carborane and acid
A solution of carborane in THF [2 mL, 5 mM, 2.0 eq] was added to a scintillation vial with a stir
bar and cooled in the cold well chilled by a dry ice
-
acetonitrile bath [
−
40
°
C]. A pre
-
cooled solution
of
acid
in THF [100 uL, 100 mM, 2.0 eq] was added, and shortly thereafter, a pre
-
cooled solution
of substrate in THF [100 uL, 50 mM, 1.0 eq] was added. The reaction was allowed to stir for one
hour. The volatiles were removed on the rotovap, and the remaining mat
erial was dissolved in
CDCl
3
[600 uL] containing
8.33 mM CH
2
Br
2
(5 umol, 1.0 eq) and analyzed by
1
H NMR.
S
6
S3. NMR SPECTRA
Figure S1.
1
H NMR spectrum of
[Ph
2
C
b
]K(
18
-
crown
-
6
)
in CD
3
CN (400 MHz).
Trimethoxybenzene was added for the Evan’s method measurement. [Ph
2
C
b
]
K(18
-
crown
-
6)
=
11.
8
mM, Δν =
18.
6 Hz
, ν = 400.15 MHz, μ
eff
=
1.
68
μ
B
Figure S
2
.
1
H NMR spectrum of
[Ph
2
C
b
][K(18
-
crown
-
6)]
2
in CD
3
CN (400 MHz)
-
1
0
1
2
3
4
5
6
7
8
9
1
0
1
1
1
2
1
3
f
1
(
p
p
m
)
4
9
.
8
4
2
.
0
0
3
.
9
7
4
.
0
4
S
7
Figure S
3
.
13
C NMR spectrum of
[Ph
2
C
b
][K(18
-
crown
-
6)]
2
in CD
3
CN (
100
MHz)
Figure S
4
.
11
B NMR spectrum of
[Ph
2
C
b
][K(18
-
crown
-
6)]
2
in CD
3
CN (
128
MHz)
-
1
0
0
1
0
2
0
3
0
4
0
5
0
6
0
7
0
8
0
9
0
1
0
0
1
1
0
1
2
0
1
3
0
1
4
0
1
5
0
1
6
0
1
7
0
1
8
0
1
9
0
2
0
0
2
1
0
f
1
(
p
p
m
)
1
0
5
1
1
0
1
1
5
1
2
0
1
2
5
1
3
0
1
3
5
1
4
0
1
4
5
1
5
0
1
5
5
1
6
0
1
6
5
f
1
(
p
p
m
)
-
4
5
-
4
0
-
3
5
-
3
0
-
2
5
-
2
0
-
1
5
-
1
0
-
5
0
5
1
0
1
5
2
0
2
5
f
1
(
p
p
m
)
1
.
0
5
2
.
0
0
1
.
0
3
0
.
9
1
S
8
Figure S
5
.
1
H
{
11
B}
NMR spectrum of
[PhC
b
Ph
N
]K(
benzo
-
15
-
crown
-
5
)
2
in CD
3
CN (400 MHz).
Trimethoxybenzene was added for the Evan’s method measurement. [PhC
b
Ph
N
] = 11.4 mM, Δν =
18.2 Hz, ν = 400.15 MHz, μ
eff
= 1.78
μ
B
Figure S
6
.
1
H
{
11
B}
NMR spectrum of
[PhC
b
Ph
NMe3
]
OTf
in CD
3
CN (400 MHz).
S
9
Figure S
7
.
11
B{
1
H} NMR spectrum of
[PhC
b
Ph
NMe3
]
OTf
in CD
3
CN (400 MHz).
Figure S
8
.
13
C{
1
H} NMR spectrum of
[PhC
b
Ph
NMe3
]
OTf
in CD
3
CN (100 MHz).
-
4
5
-
4
0
-
3
5
-
3
0
-
2
5
-
2
0
-
1
5
-
1
0
-
5
0
5
1
0
1
5
2
0
2
5
f
1
(
p
p
m
)
3
.
9
0
1
.
0
0
-
1
0
0
1
0
2
0
3
0
4
0
5
0
6
0
7
0
8
0
9
0
1
0
0
1
1
0
1
2
0
1
3
0
1
4
0
1
5
0
1
6
0
1
7
0
1
8
0
1
9
0
2
0
0
2
1
0
f
1
(
p
p
m
)
1
1
6
1
1
7
1
1
8
1
1
9
1
2
0
1
2
1
1
2
2
1
2
3
1
2
4
1
2
5
1
2
6
1
2
7
1
2
8
1
2
9
1
3
0
1
3
1
1
3
2
1
3
3
1
3
4
1
3
5
1
3
6
1
3
7
1
3
8
1
3
9
1
4
0
1
4
1
1
4
2
1
4
3
1
4
4
1
4
5
1
4
6
1
4
7
1
4
8
1
4
9
1
5
0
1
5
1
f
1
(
p
p
m
)
S
10
Figure S
9
.
19
F NMR spectrum of
[PhC
b
Ph
NMe3
]
OTf
in CD
3
CN (400 MHz).
Figure S
10
.
1
H{
11
B} NMR spectrum of
PhC
b
Ph
NMe3
in CD
3
CN (400 MHz). Trimethoxybenzene
was added for the Evan’s method measurement. [
PhC
b
Ph
NMe3
]
=
2.2
mM, Δν =
10.2
Hz, ν =
400.15 MHz, μ
eff
=
1.60
μ
B
-
2
0
0
-
1
9
0
-
1
8
0
-
1
7
0
-
1
6
0
-
1
5
0
-
1
4
0
-
1
3
0
-
1
2
0
-
1
1
0
-
1
0
0
-
9
0
-
8
0
-
7
0
-
6
0
-
5
0
-
4
0
-
3
0
-
2
0
-
1
0
0
1
0
2
0
3
0
f
1
(
p
p
m
)
S
11
Figure S11.
1
H NMR spectrum of the products of azobenzene (AB, 5
umol) reduction to 1,2
-
diphenylhydrazine (DPH) using [
PhC
b
Ph
N
]K(benzo
-
15
-
crown
-
5)
2
and [Ph
3
PH]OTf in THF with
5 umol CH
2
Br
2
as an internal standard in CDCl
3
(400 MHz).
Figure S
1
2
.
1
H NMR spectr
um
of the products of azobenzene
(AB,
5 umol) reduction
to 1,2
-
diphenylhydrazine (DPH)
using [
PhC
b
Ph
N
]K(benzo
-
15
-
crown
-
5)
2
and [Ph
3
PH]OTf in THF with
5 umol CH
2
Br
2
as an internal standard in CDCl
3
(400 MHz).
0
.
5
1
.
0
1
.
5
2
.
0
2
.
5
3
.
0
3
.
5
4
.
0
4
.
5
5
.
0
5
.
5
6
.
0
6
.
5
7
.
0
7
.
5
8
.
0
8
.
5
f
1
(
p
p
m
)
2
0
0
.
0
0
7
9
0
.
6
7
1
2
4
6
.
8
9
8
9
.
8
4
CH
2
Br
2
crown
c
rown + DPH
AB
0
.
5
1
.
0
1
.
5
2
.
0
2
.
5
3
.
0
3
.
5
4
.
0
4
.
5
5
.
0
5
.
5
6
.
0
6
.
5
7
.
0
7
.
5
8
.
0
8
.
5
f
1
(
p
p
m
)
2
0
0
.
0
0
7
9
4
.
4
3
1
2
5
6
.
4
2
7
6
.
5
0
CH
2
Br
2
crown
c
rown + DPH
AB
S
12
Figure S
1
3
.
(Top)
11
B{1H} NMR spectrum of
PhC
b
Ph
N
and (bottom)
11
B{1H} NMR spectrum
of the
products of azobenzene (AB, 5 umol) reduction to 1,2
-
diphenylhydrazine (DPH) using
[PhC
b
Ph
N
]K(benzo
-
15
-
crown
-
5)
2
and [Ph
3
PH]OTf in THF, both in CDCl
3
(400 MHz)
Figure S
1
4
.
1
H NMR spectr
um
of the products of 1,2
-
bis
-
(4
-
bromo
phenyl
)diazene (
DA,
5 umol)
reduction
to 1,2
-
bis(4
-
bromophenyl)hydrazine (DPH)
using [PhC
b
Ph
N
]K(benzo
-
15
-
crown
-
5)
2
and [Ph
3
PH]OTf in THF with 5 umol CH
2
Br
2
as an internal standard in CDCl
3
(400 MHz).
-
2
4
-
2
2
-
2
0
-
1
8
-
1
6
-
1
4
-
1
2
-
1
0
-
8
-
6
-
4
-
2
0
2
4
6
8
1
0
1
2
1
4
1
6
1
8
2
0
2
2
f
1
(
p
p
m
)
0
.
5
1
.
0
1
.
5
2
.
0
2
.
5
3
.
0
3
.
5
4
.
0
4
.
5
5
.
0
5
.
5
6
.
0
6
.
5
7
.
0
7
.
5
8
.
0
8
.
5
f
1
(
p
p
m
)
2
0
0
.
0
0
3
1
9
.
4
2
4
0
.
2
3
C
H
2
B
r
2
D
P
H
D
A
S
13
Figure S
1
5
.
1
H NMR spectr
um
of the products of 1,2
-
di
-
p
-
tolyldiazene (
DA,
5 umol) reduction
to
1,2
-
di
-
p
-
tolylhydrazine (DPH)
using [PhC
b
Ph
N
]K(benzo
-
15
-
crown
-
5)
2
and [Ph
3
PH]OTf in THF
with 5 umol CH
2
Br
2
as an internal standard in CDCl
3
(400 MHz).
Figure S
1
6
.
1
H NMR spectr
um
of the products of 1,2
-
bis
-
(4
-
methoxy
phenyl
)diazene (
DA,
5 umol)
reduction
to 1,2
-
bis(4
-
methoxyphenyl)hydrazine (DPH)
using [PhC
b
Ph
N
]K(benzo
-
15
-
crown
-
5)
2
and [Ph
3
PH]OTf in THF with 5 umol CH
2
Br
2
as an internal standard in CDCl
3
(400 MHz).
Note
that peaks of the
hydrazine
product
at 6.75 and 6.66 ppm (marked with arrow) are not observed.
0
.
5
1
.
0
1
.
5
2
.
0
2
.
5
3
.
0
3
.
5
4
.
0
4
.
5
5
.
0
5
.
5
6
.
0
6
.
5
7
.
0
7
.
5
8
.
0
8
.
5
f
1
(
p
p
m
)
2
0
0
.
0
0
1
7
1
.
5
8
2
5
5
.
8
2
C
H
2
B
r
2
D
P
H
D
A
S
14
Figure S
17
.
1
H NMR spectrum of the products of acetophenone (5 umol) reduction
using
[PhC
b
Ph
N
]K(benzo
-
15
-
crown
-
5) and [Ph
3
PH]OTf in THF with 5 umol
CH
2
Br
2
as an internal
standard in CDCl
3
(400 MHz).
Figure S
18
.
1
H NMR spectrum of the products of
diphenyl fumarate
(5 umol) reduction
to
diphenyl
succinate
using [PhC
b
Ph
N
]K(
benzo
-
15
-
crown
-
5
) and [Ph
3
PH]OTf in
THF with 5 umol
CH
2
Br
2
as an internal standard in CDCl
3
(400 MHz).
0
.
5
1
.
0
1
.
5
2
.
0
2
.
5
3
.
0
3
.
5
4
.
0
4
.
5
5
.
0
5
.
5
6
.
0
6
.
5
7
.
0
7
.
5
8
.
0
8
.
5
f
1
(
p
p
m
)
2
6
6
.
3
6
2
0
0
.
0
0
1
7
4
.
1
5
a
c
e
t
o
p
h
e
n
o
n
e
-
C
H
3
C
H
2
B
r
2
a
c
e
t
o
p
h
e
n
o
n
e
o
-
P
h
H
0
.
5
1
.
0
1
.
5
2
.
0
2
.
5
3
.
0
3
.
5
4
.
0
4
.
5
5
.
0
5
.
5
6
.
0
6
.
5
7
.
0
7
.
5
8
.
0
8
.
5
f
1
(
p
p
m
)
2
9
1
.
0
3
2
0
0
.
0
0
C
H
2
B
r
2
s
u
c
c
i
n
a
t
e
S
15
Figure S
19
.
1
H NMR spectrum of a 200 uL aliquot of the substrate solution for the competition
experiment (H vs. Me), approximately 11 umol each, after concentration
in vacuo
with 5 umol
CH
2
Br
2
as an internal standard in CDCl
3
(400 MHz).
Figure S
2
0
.
1
H NMR spectrum of the products
of the
azoarene competition experiment
(H vs. Me,
run A)
with substrates (11 umol) using [PhC
b
Ph
N
]K(benzo
-
15
-
crown
-
5) and [Ph
3
PH]OTf in THF
with 5 umol CH
2
Br
2
as an internal standard in CDCl
3
(400 MHz).
0
.
5
1
.
0
1
.
5
2
.
0
2
.
5
3
.
0
3
.
5
4
.
0
4
.
5
5
.
0
5
.
5
6
.
0
6
.
5
7
.
0
7
.
5
8
.
0
8
.
5
f
1
(
p
p
m
)
2
0
0
.
0
0
8
5
2
.
8
5
8
7
1
.
1
0
C
H
2
B
r
2
H
M
e
0
.
5
1
.
0
1
.
5
2
.
0
2
.
5
3
.
0
3
.
5
4
.
0
4
.
5
5
.
0
5
.
5
6
.
0
6
.
5
7
.
0
7
.
5
8
.
0
8
.
5
f
1
(
p
p
m
)
2
0
0
.
0
0
3
1
8
.
5
9
8
5
2
.
4
7
8
7
3
.
5
5
7
0
5
.
0
6
C
H
2
B
r
2
H
M
e