Supporting
i
nformation
for:
Highly Selective Fe
-
Catalyzed Nitrogen Fixation to Hydrazine Enabled by
Sm(II) Reagents with Tailored Redox Potential and pK
a
Emily A. Boyd and Jonas C. Peters
*
Division of Chemistry and Chemical Engineering,
California Institute of Technology, Pasadena,
California 91125, United States
*E
-
mail:
jpeters@caltech.edu
Contents
S1. Experimental Part
................................
................................
................................
.....................
3
S1.1 General Considerations
................................
................................
................................
.......
3
S1.2 Nuclear Magnetic Resonance (NMR) Spectroscopy
................................
..........................
3
S1.3 Electron Paramagnetic Resonance (EPR) Spectroscopy
................................
....................
3
S1.4
57
Fe Mössbauer Spectroscopy
................................
................................
.............................
3
S1.5 Infrared (IR) Spectrocopy
................................
................................
................................
...
4
S1.6 Electrochemistry
................................
................................
................................
.................
4
S2. Hydrazine and Ammonia Generation Detail
s
................................
................................
...........
5
S2.1 Standard N
2
H
4
/NH
3
Generation Reaction Procedure
................................
.........................
5
S2.2 Ammonia and Hydrazine Quantification
................................
................................
............
5
S2.3 Me
2
NNH
2
/Me
2
NH Generation and Quantification Procedure
................................
..........
6
S2.4 Catalytic Runs
................................
................................
................................
.....................
7
S3. NMR Spectroscopy
................................
................................
................................
.................
12
S3.1 Procedure for Quantification of Sm
-
Containing Byproducts of Catalysis
.......................
12
S3.2 Procedure for NMR Titrations
................................
................................
..........................
12
S4. EPR Spectroscopy
................................
................................
................................
..................
18
S4.1 General Procedure for Preparation of Freeze
-
quench EPR Samples of Catalytic Reaction
Mixtures
................................
................................
................................
................................
....
18
S4.2 General Procedure for Preparation of EPR Samples of the Reaction of Fe complexes with
Sm
II
Reductants
................................
................................
................................
.........................
18
S5.
57
Fe Mössbauer Spectroscopy
................................
................................
................................
.
26
2
S5.1 General Procedure for Preparation of Freeze
-
quench Mössbauer Samples of Catalytic
Reaction Mixtures
................................
................................
................................
.....................
26
S5.2 Procedure for Preparation of Mössbauer Sample of the Reaction of FeN
2
with Sm
II
......
26
S5.3 Comments on the Mössbauer Spectra
................................
................................
...............
27
S6. IR Spectroscopy
................................
................................
................................
......................
28
S7. Electrochemistry
................................
................................
................................
.....................
29
S8. References
................................
................................
................................
...............................
30
3
S
1.
Experimental Part
S
1.1
General
Considerations
All manipulations were carried out using standard Schlenk or glovebox techniques under an N
2
atmosphere. Unless otherwise noted, solvents were deoxygenated and dried by thoroughly
sparging with N
2
gas followed by passage through an activat
ed alumina column in the solvent
purification system by SG Water, USA LLC. Non
-
halogenated solvents were tested with a
standard purple solution of sodium benzophenone ketyl in tetrahydrofuran to confirm effective
oxygen and moisture removal. All reagents w
ere purchased from commercial vendors and used
without
further purification
unless otherwise stated.
2
-
methyltetrahydrofuran (2
-
MeTHF) was
degassed and stored over 4
Å molecular sieves and then stirred over NaK and passed over
activated alumina immediately
before use.
MeOH
was
stirred over 3
Å
molecular sieves under
N
2
for one week, vacuum transferred into a Schlenk flask, and stored sealed in a glovebox.
N
-
methylpyrrolidon
e
(PMe)
,
2
-
pyrrolidone
(PH)
, hexamethylphosphoramide (HMPA)
, and
diisopropylamine (
i
Pr
2
NH)
were degassed and passed over a pipet filter of activated alumina.
5
-
(trifluoromethyl)pyrrolidone
was dried by dissolving in Et
2
O and passing over a pipet filter of
activated alumina.
n
Bu
4
NPF
6
was recrystallized from hot EtOH three times and then dried under
vacuum at 100°C for >12 hours before use as electrolyte.
15
N
2
(99%) was obtained from
Cambridge Isotope Laboratories, Inc.
2
-
pyrrolidone was deuterated by stirring in CD
3
OD for 30
minutes f
ollowed by removal of solvent
in vacuo
(75% deuteration measured by
1
H NMR).
Me
2
NNH
3
Cl was generated by treatment of Me
2
NNH
2
with excess of a solution of HCl in Et
2
O
at −78°C followed by removal of solvent
in vacuo
.
(
t
Bu
2
ArO)
2
Me
2
cyclam)Sm
(
Sm
II
),
1,2
[
Sm
III
]PF
6
,
2,3
SmI
2
(THF)
2
,
4
P
3
B
FeN
2
(
Fe
N
2
)
,
5
Fe
BAr
F
4
,
6
Fe
NNMe
2
,
7
and
[
D
BUH]OTf
8
were
synthesized via
reported
lit
erature procedures.
S
1.2 Nuclear Magnetic Resonance
(NMR)
Spectroscopy
Deuterated solvents were purchased from Cambridge Isotope Laboratories, Inc. C
6
D
6
was
degassed, stirred over NaK, and passed over activated alumina before use.
CD
3
CN was
degassed
and passed over a pipet filter of activated alumina five times immediately before use.
1
H
chemical shifts are reported in ppm relative to tetramethylsilane, using residual solvent
resonances as internal standards.
9
15
N chemical shifts are
referenced to CH
3
NO
2
following the
recommended scale based on ratios of absolute frequencies (Ξ).
10
S
1.3 Ele
ctron Paramagnetic Resonance
(EPR)
Spectroscopy
X
-
band EPR spectra were obtained on a Bruker EMX spectrometer. Samples were collected at
a
power of
2 mW
with modulation amplitudes of 2.00 G, and modulation frequencies of 100.00
kHz. EPR spectra were modeled using the easyspin program.
11
S
1.4
57
Fe Mössbauer
Spectroscopy
Mössbauer spectra were recorded on a spectrometer from SEE Co. (Edina, MN) operating in the
constant acceleration mode in a transmission geometry. The sampl
es were
kept in an SVT
-
400
cryostat from Janis (Wilmington, MA). The quoted isomer sh
ifts are relative to the centroid of
4
the spectrum of a metallic foil of α
-
Fe at room temperature. Data analysis was performed using
version 4 of the program WMOSS (www.wmoss.org) and quadrupole doublets were fit to
Lorentzian lineshapes.
S
1.5 Infrared (IR
) Spectrocopy
IR measurements were obtained as thin films formed by evaporation of solutions using a Bruker
Alpha Platinum ATR spectrometer with OPUS software.
S
1.6 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 CD
instruments 600B electrochemical analyzer was used for data collection. A glassy carbon disk (3
mm diameter) was used as the working electro
de. It was freshly polished with 1, 0.3, and 0.05
μm alumina powder water slurries and rinsed with water and acetone before use. A silver wire
immersed in a 5 mM solution of AgOTF in electrolyte separated from the working solution by a
frit was used as pse
udoreference and a platinum wire was used as the auxiliary electrode. Cyclic
voltammograms (CVs) are plotted using IUPAC convention.
For all measurements IR
compensation was applied accounting for 85% of the total resistance.
All reported potentials are
re
ferenced to the ferrocene couple, Cp
2
Fe
+
/Cp
2
Fe measured at the end of each electrochemical
experiment. Electrochemistry solvents were passed over a pipet filter of activated alumina
immediately before use.
5
S
2.
Hydrazine and Ammonia Generation Details
S
2.1 Standard N
2
H
4
/NH
3
Generation Reaction Procedure
All solvents are stirred with Na/K for ≥ 2 hours and filtered over activated alumina prior to use.
In a nitrogen
-
filled glovebox, a long tube with a female 24/40 joint at the top is charged with the
Sm
II
reductant as a solid
(and HMPA as a liquid in reacti
ons with this additive)
. The tube is then
sealed at room temperature with a septum that is secured with copper wire. The tube is chilled
in
a
glovebox cold well immersed in a dry ice/acetone bath
and allowed to equilibrate for 10
minutes. To the chilled tu
be is added 1 mL of
a
room temperature solution of the acid
and/
or
PMe via syringe. The
contents of the
tube
are
stirred and warmed for five minutes to dissolve the
reductant. The tube is again chilled at −78°C for 10 minutes. A 1 mM solution of
the Fe
pre
catalyst
is similarly chilled. A 0.5 mL aliquot of this solution
(0.5 μmol)
is added to the tube
via syringe and the mixture is allowed to stir and warm to room temperature overnight
(≥ 12 h)
.
In the case of lower catalyst loadings, smaller volumes of the
1 mM Fe solution are added to the
tube along with additional chilled
solvent
to achieve
the desired Fe loading and
a total reaction
volume of 1.5 mL.
The tube is then brought out of the glovebox and analyzed for NH
3
and N
2
H
4
.
For the catalytic run conducted under
15
N
2
, the standard procedure is modified as follows: after
premixing
Sm
II
(50 mg, 60 μmol) and PH (4.2 mg, 48 μmol) in 1 mL toluene as described above
in a Schlenk tube, an additional 0.5 mL of toluene is added. The re
action mixture is then
degassed (three freeze
-
pump
-
thaw cycles, thawing only to −78°C). The degassed reaction
mixture is frozen
in a liquid nitrogen
-
cooled cold well
under vacuum. The tube is opened and 50
μL of a 10 mM solution of P
3
B
FeN
2
(0.5
μmol) is ad
ded along the wall of the tube. The tube is
allowed to equilibrate at 77K for 5 minutes and evacuated. It is then warmed to −78°C,
backfilled with
15
N
2
, and allowed to stir at −78°C for 24 hours.
S2.2 Ammonia and Hydrazine Quantification
Reaction mixtures are cooled to 77 K and allowed to freeze. HCl (3 mL of a 2.0 M solution in
Et
2
O, 6 mmol) is added to the frozen tube via syringe
over 1
-
2 minutes
and allowed to freeze.
The septum on the tube is then exchanged for a Schlenk tube adapter a
nd the headspace of the
tube is evacuated. After sealing the tube, it is then allowed to warm to room temperature and
stirred at room temperature for at least 10 minutes.
Solvent is removed
in vacuo
, and the solids
are extracted with 1 M HCl(aq) and filter
ed to give a total solution volume of 10 mL. From this
solution, a 200 μL aliquot is analyzed for the presence of NH
3
(present as NH
4
Cl) by the
indophenol method.
12
Quantification was performed with UV
-
vis spectroscopy by analyzing the
absorbance at 635 nm
using a calibration curve
.
13
A further 200 μL aliquot of this solution was
analyzed for the presence of N
2
H
4
(present as N
2
H
5
Cl) by a standard colorimetric method
.
14
Quantification was performed with UV
-
vis spectroscopy by analyzing the absorbance at 458 nm
using a calibration curve.
15
For the catalytic run conducted under
15
N
2
, the solid residue
remaining after quenching with HCl in Et
2
O was extracted into DMSO
-
d
6
and analyzed by
15
N{
1
H} NMR spectroscopy.
The presence of HMPA in catalytic reaction mixtures was found to interfere with the indophenol
method for ammonia quantification. An alternative procedure was therefore employed to
quantify ammonia from reactions with HMPA. A Schlenk tube is charged with H
Cl (3 mL of a
6
2.0 M solution in Et
2
O, 6 mmol) to serve as a collection flask. The volatiles of the reaction
mixture are vacuum transferred at RT into this collection flask. After completion of the vacuum
transfer, the collection flask is sealed and warmed
to RT. Solvent is removed
in vacuo
, and the
remaining residue is dissolved in 0.7 mL of DMSO
-
d
6
containing 1,3,5
-
trimethoxybenzene as an
internal standard. The
1
H NMR signal observed for NH
4
+
is then integrated against the two peaks
of trimethoxybenzene to
quantify the ammonium present.
S2.3 Me
2
NNH
2
/Me
2
NH Generation and Quantification Procedure
All solvents are stirred with Na/K for ≥ 2 hours and filtered over activated alumina prior to use.
In a nitrogen
-
filled glovebox, a Schlenk tube is charged with t
he Sm
II
reductant as a solid (15.3
mg, 19 μmol). The tube is chilled in a glovebox cold well immersed in a dry ice/acetone bath and
allowed to equilibrate for 10 minutes. To the chilled tube is added 1 mL of a room temperature
solution of PH in toluene (15
mM, 15 μmol) via syringe. The contents of the tube are stirred and
warmed for five minutes to dissolve the reductant. The tube is again chilled at −78°C for 10
minutes. A 10 mM solution of
Fe
NNMe
2
is similarly chilled. A 0.5 mL aliquot of this solution (5
μmol) is added
, the tube is sealed,
and the mixture is allowed to stir for 5 min
utes
, at which point
Sm
II
–
PH is fully consumed as judged by the disappearance of its dark green color. The tube is
then frozen in liquid nitrogen. A solution of NaO
t
Bu
in MeOH (1 mL of a 0.2 M solution,
0.2
mmol) is added along the walls of the tube. The tube is resealed and the headspace is evacuated.
The mixture is allowed to warm and stir at room temperature for 20 minutes. A second Schlenk
tube is charged with HCl (
3 mL of a 2.0 M solution in Et
2
O, 6 mmol) to serve as a collection
flask. The volatiles of the quenched reaction mixture are vacuum transferred at RT into this
collection flask. After completion of the vacuum transfer, the collection flask is sealed and
wa
rmed to RT. Solvent is removed
in vacuo
, and the remaining residue is dissolved in 0.6 mL of
CD
3
OD containing 1,3,5
-
trimethoxybenzene as an internal standard. The
1
H NMR signals
observed for the methyl protons of Me
2
NH
2
+
(2.70 ppm) and Me
2
NNH
3
+
(2.91 ppm)
are then
integrated against the methyl peak of trimethoxybenzene to quantify their production.
7
S
2.
4
Catalytic Runs
Table S
1
.
Catalytic runs
with variable catalyst loading
(toluene, −78°C, 12 h)
Entry
μmol
Fe
N
2
Acid
(equiv)
Reductant
(equiv)
equiv NH
3
(%)
equiv N
2
H
4
(%)
Total
Fixed
-
N
% Yield
A
0.50
PH
(96)
Sm
II
(120)
0.78
(2.4)
14.4
(59.5)
61.9
B
0.50
PH
(96)
Sm
II
(120)
0.74
(2.3)
18.4
(76.6)
78.9
C
0.50
PH
(96)
Sm
II
(120)
−
13.8
(57.1)
−
Average
0.50
PH
(96)
Sm
II
(120)
0.76 ±
0.03
(2.4 ± 0.1)
16 ± 3
(64 ± 11)
6
7
± 11
D
0.18
PH
(
260
)
Sm
II
(
325
)
<0.1
(<0.3)
41.1
(60.3)
60.3
E
0.18
PH
(260)
Sm
II
(325)
<0.1
(<0.3)
32.8
(48.1)
48.1
Average
0.18
PH
(260)
Sm
II
(325)
<0.1
(<0.3)
37 ± 6
(54 ± 9)
54 ± 9
F
0.10
PH
(
480
)
Sm
II
(
600
)
<0.1
(<0.3)
43.1
(35.8)
35.8
G
0.10
PH
(480)
Sm
II
(600)
<0.1
(<0.3)
48.8
(40.5)
40.5
Average
0.10
PH
(480)
Sm
II
(600)
<0.1
(<0.3)
46 ± 4
(38 ± 3)
38 ± 3
H
0.05
a
PH
(96
0
)
Sm
II
(120
0
)
<0.1
(<0.3)
69
(29)
29
I
0.05
a
PH
(96
0
)
Sm
II
(120
0
)
<0.1
(<0.3)
38
(16)
16
Average
0.05
a
PH
(96
0
)
Sm
II
(120
0
)
<0.1
(<0.3)
53 ± 20
(38 ± 3)
22 ± 9
J
0
PH
(48 μmol)
Sm
II
(60 μmol)
−
(<0.3)
−
(<1)
<1.3
K
0
PH
(48 μmol)
Sm
II
(60 μmol)
−
(<0.3)
−
(<1)
<1.3
Average
0
PH
(48 μmol)
Sm
II
(60 μmol)
−
(<0.3)
−
(<1)
<1.3
a
72 h.
b
48 h.
8
Table S
2
.
Catalytic runs with variable reductant
(0.5 μmol
Fe
N
2
, toluene, −78°C, 12 h)
Entry
Acid (equiv)
Reductant (equiv)
equiv NH
3
(%)
equiv N
2
H
4
(%)
Total
Fixed
-
N
% Yield
A
PH
(96)
SmI
2
(THF)
2
(120)
<0.1
(<0.3)
<0.3
(<1)
<1.3
B
PH
(96)
SmI
2
(THF)
2
(120)
<0.1
(<0.3)
<0.3
(<1)
<1.3
Average
PH
(96)
SmI
2
(THF)
2
(120)
<0.1
(<0.3)
<0.3
(<1)
<1.3
C
PH
(96)
SmI
2
(THF)
2
(120)
+ HMPA (240)
0.56
(
1.8
)
-
-
D
PH
(96)
SmI
2
(THF)
2
(120)
+ HMPA (240)
0.18
(
0.6
)
-
-
E
PH
(96)
SmI
2
(THF)
2
(120)
+
HMPA (240)
-
0.97
(4.0)
-
F
PH
(96)
SmI
2
(THF)
2
(120)
+ HMPA (240)
-
0.3
(1.3)
-
Average
PH
(96)
SmI
2
(THF)
2
(120)
+ HMPA (240)
0.4 ± 0.3
(1.2 ± 0.8)
0.6 ± 0.4
(3 ± 2)
4 ± 2
G
PH
(96)
SmI
2
(THF)
2
(120)
+ HMPA (240)
<0.1
(<0.3)
-
-
H
PH
(96)
SmI
2
(THF)
2
(120)
+ HMPA (240)
<0.1
(<0.3)
-
-
I
PH
(96)
SmI
2
(THF)
2
(120)
+ HMPA (240)
-
3.15
(
13.1
)
-
J
PH
(96)
SmI
2
(THF)
2
(120)
+ HMPA (240)
-
3.08
(1.3)
-
Average
PH
(96)
SmI
2
(THF)
2
(120)
+ HMPA (480)
<0.1
(<0.3)
3.1
± 0.1
(
12.9
± 0.
2
)
12.9 ± 0.2
9
Table S
3
.
Catalytic runs with variable acid
(0.5 μmol
Fe
N
2
,
toluene,
−78°C, 1
2
h)
Entry
Acid (equiv)
Reductant
(equiv)
equiv NH
3
(%)
equiv N
2
H
4
(%)
Total Fixed
-
N
% Yield
A
none
(96)
Sm
II
–
PMe
(120)
<0.1
(<0.3)
<0.3
(<1)
<1.3
B
none
(96)
Sm
II
–
PMe
(120)
<0.1
(<0.3)
<0.3
(<1)
<1.3
Average
none
(96)
Sm
II
–
PMe
(120)
<0.1
(<0.3)
<0.3
(<1)
<1.3
C
CF3
PH
(96)
Sm
II
(120)
1.6
(4.9)
10.8
(44.8)
49.8
D
CF3
PH
(96)
Sm
II
(120)
2.1
(6.5)
11.0
(45.9)
52.3
Average
CF3
PH
(96)
Sm
II
(120)
1.8 ± 0.3
(6 ± 1)
10.9 ± 0.2
(45.3 ± 0.7)
51 ± 2
E
MeOH
(96)
Sm
II
(120)
2.0
(6.3)
6.4
(26.6)
32.9
F
MeOH
(96)
Sm
II
(120)
2.9
(8.9)
6.2
(25.7)
34.6
Average
MeOH
(96)
Sm
II
(120)
2.4 ± 0.6
(8 ± 2)
6.3 ± 0.2
(26.1 ± 0.6)
34 ± 1
G
[DBUH]OTf
(96)
Sm
II
–
PMe
(120)
<0.1
(<0.3)
3.2
(13.2)
13.2
H
[DBUH]O
t
f
(96)
Sm
II
–
PMe
(120)
<0.1
(<0.3)
1.6
(6.8)
6.8
Average
[DBUH]O
t
f
(96)
Sm
II
–
PMe
(120)
<0.1
(<0.3)
2.4 ± 1
(10 ± 4)
10 ± 4
I
PD
(96)
Sm
II
(120)
0.84
(2.6)
11.7
(
48.7
)
51.3
J
PD
(96)
Sm
II
(120)
1.14
(3.6)
12.4
(
51.8
)
5
5.4
Average
PD
(96)
Sm
II
(120)
1.0 ± 0.2
(3.1 ± 0.6)
12.1
± 0.5
(
50
± 2)
53
±
3
K
CD
3
OD
(96)
Sm
II
(120)
5.6
(17.6)
7.4
(30.7)
48.2
L
CD
3
OD
(96)
Sm
II
(120)
5.8
(18.0)
8.1
(33.6)
51.6
Average
CD
3
OD
(96)
Sm
II
(120)
5.7 ± 0.1
(17.8 ± 0.3)
7.7 ± 0.5
(32 ± 2)
50 ± 2
10
S2.
4.1
Discussion of Isotope Effect
Deuteration of the acid sources in the catalytic reactions reveals an
H/D
isotope effect on the
selectivity of the N
2
RR. The N
2
H
4
:NH
3
ratio with PH ((21 ± 4):1 at 96 equiv
acid loading) drops
to (12 ± 2.5):1 with PD (compare entries A, B in Table S1 to entries I, J in Table S3). Similarly,
the N
2
H
4
:NH
3
ratio with MeOH (
(2.6 ± 0.7):1) drops to (1.4 ± 0.1):1 with CD
3
OD (compare
entries E,F to entries K,L in Table S3). These d
ata suggest
that while stronger acids favor the
NH
3
-
evolving pathway, the N
2
H
4
-
evolving pathway has a higher
primary
H/D isotope effect than
the NH
3
pathway. We note that this observation has many possible reasonable interpretations. As
just one example, a
plausible
N
2
H
4
-
evolving pathway
is given by
A below, which comprises
preequilibrium ET to FeNNH
2
to form
[
FeNNH
2
][
Sm
III
–
EH]
followed by irreversible PT to N
α
.
This path might
be expected to have a larger isotope effect (equivalent to the KIE of the PT
step)
than the NH
3
-
evolving pathway
shown in
B, which comprises preequilibrium PT
(or a hydrogen
-
bonding interaction)
to N
β
of FeNNH
2
,
followed by N
–
N bond cleavage (the isotope effect
would be equivalent to the EIE of the preequilibrium PT
, or hydrogen
-
bo
nding, step
).
T
his
discussion
bears a striking similarity
to observations in oxygen reduction literature: stronger
acids promote O
–
O bond cleavage in Fe
III
–
O
–
OH complexes via protonation of O
β
to form H
2
O
,
and
a small inverse
H/D
isotope effect has been ob
served for
this reaction
.
16
11
Table S
4
.
Additional catalytic runs (0.5 μmol
precatalyst
, −78°C, 1
2
h)
Entry
Precatalyst
Solvent
Acid
(equiv)
Reductant
(equiv)
equiv NH
3
(%)
equiv N
2
H
4
(%)
Total
Fixed
-
N
% Yield
A
Fe
N
2
THF
PH
(96)
SmI
2
(THF)
2
(120)
<0.1
(<0.3)
<0.3
(<1)
<1.3
B
Fe
N
2
THF
PH
(96)
SmI
2
(THF)
2
(120)
<0.1
(<0.3)
<0.3
(<1)
<1.3
Average
Fe
N
2
THF
PH
(96)
SmI
2
(THF)
2
(120)
<0.1
(<0.3)
<0.3
(<1)
<1.3
C
Fe
N
2
THF
PH
(96)
Sm
II
(120)
<0.1
(<0.3)
3.3
(13.5)
13.5
D
Fe
N
2
THF
PH
(96)
Sm
II
(120)
<0.1
(<0.3)
3.7
(15.3)
15.3
Average
Fe
N
2
THF
PH
(96)
Sm
II
(120)
<0.1
(<0.3)
3.5 ± 0.3
(14 ± 1)
14 ± 1
E
Fe
N
2
toluene
PH
(96)
Sm
II
(96)
<0.1
(<0.3)
9.7
(40.4)
40.4
F
Fe
N
2
toluene
PH
(96)
Sm
II
(96)
<0.1
(<0.3)
9.6
(39.9)
39.9
Average
Fe
N
2
toluene
PH
(96)
Sm
II
(96)
<0.1
(<0.3)
9.7 ± 0.1
(40.2 ± 0.3)
40.2 ± 0.3
G
Fe
N
2
toluene,
+ PMe
(192)
PH
(96)
Sm
II
(96)
0.4
(
1.4
)
10.4
(
43.3
)
40.4
J
Fe
N
2
toluene,
+ PMe
(192)
PH
(96)
Sm
II
(96)
0.2
(
0.5
)
10.1
(
42.0
)
39.9
Average
Fe
N
2
toluene,
+ PMe
(192)
PH
(96)
Sm
II
(96)
0.3 ± 0.2
(
0.9 ± 0.6
)
10.3
± 0.
2
(4
3
±
1
)
4
4
±
2
I
Fe
BAr
F
4
Et
2
O
PH
(96)
Sm
II
(120)
<0.1
(<0.3)
5.9
(24.5)
24.5
J
Fe
BAr
F
4
Et
2
O
PH
(96)
Sm
II
(120)
<0.1
(<0.3)
6.3
(26.1)
26.1
Average
Fe
BAr
F
4
Et
2
O
PH
(96)
Sm
II
(120)
<0.1
(<0.3)
6.1 ± 0.3
(25 ± 1)
25 ± 1