S1
Supporting information for
Photodriven Sm(III)-to-Sm(II) reduction for catalytic applications
Christian M. Johansen,
‡
Emily A. Boyd,
‡
Drew E. Tarnopol and Jonas C. Peters*
Correspondence to: jpeters@caltech.edu
Table of Contents:
S2-3
S1. Materials and Methods
S4-18
S2. Catalytic ketone-olefin coupling reactions
S19-43
S3. UV-vis experiments
S43-49
S4. Electrochemical methods
S50-51
S5. Additional Mechanistic schemes
S52
S6. References
S2
S1.1 Materials and Methods
All manipulations were carried out using standard Schlenk or glovebox techniques under an N
2
atmosphere. 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.
Nonhalogenated solvents were tested with sodium benzophenone ketyl in tetrahydrofuran (THF) to
confirm the absence of oxygen and water. Deuterated solvents were purchased from Cambridge Isotope
Laboratories, Inc.
Phenyl acrylate was purchased from Ambeed, degassed, and used without further purification.
Cyclohexanedione monoethylene ketal (
1
)
was purchased from TCI and used without further purification.
All bases (DBU, Et
3
N, pyridine, 2,6-lutidine) were purchased from Sigma Aldrich and distilled prior to use.
Sm(OTf)
3
, Gd(OTf)
3
, and MgI
2
were purchased from Sigma–Aldrich. Ir(ppy)
2
(dtbbpy)[PF
6
] was purchased
from Strem and used without further purification. 3DPA2FBN (2,4,6-tris(diphenylamino)-3,5-
difluorobenzonitrile) was purchased from Ambeed and used without further purification. 9,10-
dihydroacridine was purchased from Combi-blocks and purified by sublimation prior to use.
Hexamethylphosphoramide, ethylene glycol, and
2-(2-(2-methoxyethoxy)ethoxy)ethan-1-ol were
purchased from Sigma Aldrich and degassed. Tetraheptylammonium iodide was purchased from TCI and
dried at 100°C under dynamic vacuum for 16 hours. Tetrabutylammonium bromide was acquired from
Strem and then dried by heating to 85°C for 48 hours under dynamic vacuum using P
2
O
5
as a desiccant. 1-
Butyl-1-methylpiperidinium (BMPipTFSI) was purchased from TCI chemicals and used without further
purification.
SmI
2
(THF)
2
,
1
phenH
2
,
2
BINAPO,
3
aminodiol (L*),
4
and [LutH]TFSI
5
were synthesized following
literature procedures.
HEH
2
6
synthesized following literature procedure and then dried by heating to 80 °C for 24 hours
under dynamic vacuum using P
2
O
5
as a desiccant.
The 2-MeTHF used was dried extensively prior to use in ketyl-olefin coupling experiments.
Inhibitor-free solvent was refluxed over CaH
2
for 24 hours (under N
2
atmosphere) and distilled into a
Strauss flask. This flask was brought into the glovebox, where NaK was added, and the solvent was
stirred for 24 hours. The solvent was then vacuum transferred into a fresh Strauss flask and stored over
activated sieves.
S1.2
Physical Methods
NMR:
Nuclear Magnetic Resonance (NMR) measurements were recorded with a Varian 400 MHz
spectrometer.
1
H NMR chemical shifts are reported in ppm relative to tetramethylsilane, using
1
H
resonances from residual solvent as internal standards.
UV-Vis:
Ultraviolet-visible (UV-vis) absorption spectroscopy measurements were collected with a Cary
50 UV-vis spectrophotometer using a 1 cm path length quartz cuvette. All samples had a blank sample
background subtraction applied. Temperature regulation for UV-Vis measurements was carried out with a
Unisoku cryostat.
Electrochemistry:
All electrochemical experiments were conducted using a CH instruments 600B
electrochemical analyzer. A nonaqueous Ag
+/0
reference electrode (BASi) consisting of a silver wire
immersed in 5 mM AgOTf in DME containing 0.2 M
n
Bu
4
NPF
6
separated from the working solution by a
CoralPor® frit was used for all experiments. All reported potentials are referenced to the
ferrocenium/ferrocene (Fc
+/0
) couple used as an external standard. All CVs were carried out in an N
2
-filled
S3
glovebox in a 20 mL scintillation vial fitted with a septum cap containing punched-out holes for insertion
of electrodes. A glassy carbon disk (3 mm diameter) was used as the working electrode for all CVs. It was
freshly polished with 1, 0.3, and 0.05 μm alumina powder water slurries, rinsed with water and acetone,
and dried before use. A platinum wire was used as the auxiliary electrode for CVs. CVs are plotted using
IUPAC convention. Unless otherwise noted, IR compensation was applied, accounting for 85% of the total
resistance.
S4
S2 Catalytic ketone-olefin coupling reactions
S2.1.1 Standard procedure in the absence of Ir-photocatalyst
In the glovebox, HEH
2
(40.4 mg, 160 μmol) was added as a solid to a Schlenk flask. 2-MeTHF
(0.5 mL) was added to the flask. A freshly prepared stock solution of SmI
2
(THF)
2
in 2-MeTHF (2.2 mg
per mL, 4 mM) was added to the flask (1 mL added). A stock solution of the remaining organics: ketone
(12.6 mg per mL; 80 mM), phenyl acrylate (22 μL per mL; 160 mM), and when noted base was prepared,
and 0.5 mL was added to the reaction flask. The color of SmI
2
(purple) rapidly changes to yellow upon
the addition of the organic reagents. The reaction flask is sealed and brought out of the glovebox, where it
is irradiated by two H160 PR Kessil™ 440 nm Blue LED lamps for 90 minutes in a water bath in a
reflective dewar. The reaction was continuously stirred (1200 rpm). The temperature of the water bath
was monitored and did not exceed 25 °C during the reaction. A picture of the setup is shown in Figure S2.
Following completion of the reaction, the flask was opened to air, and 2 mL Et
2
O was added. The
contents of the flask was filtered through a silica plug into a vial containing a known amount of 1,3,5-
trimethoxybenzene (TMB; ~7 mg). The reaction flask was washed with additional Et
2
O (2x1 mL), and the
washes were passed through the silica plug into the vial. The solvent was removed
in vacuo
and the
products were taken up in CDCl
3
and analyzed by
1
H NMR integrating against the TMB standard.
Lactone product
(
2
;
1,4,9-trioxadispiro[4.2.48.25]tetradecan-10-one) is detected by
1
H NMR with
features matching literature spectra (Figure S4).
Note:
This reaction is very sensitive to the method of solvent drying and the CaH
2
/NaK-method laid out
in the general considerations is required. Similarly, the HEH
2
must be dried as described. The reaction is
sensitive to both water and air as shown in Table S2.
S2.1.2 Standard procedure with an Ir-photocatalyst
In the glovebox, Ir(ppy)
2
(dtbbpy)[PF
6
] (0.36 mg, 0.4 μmol) was dissolved in THF and added to a
Schlenk flask, and the solvent was removed
in vacuo
, depositing a thin film. Following this HEH
2
,
SmI
2
(THF)
2
and organics were added as described in
S2.1.1
S5
S2.2 Yields for ketone-olefin coupling reactions
O
OPh
O
O
SmI
2
(THF)
2
(10 mol %)
HEH
2
(4.0 equiv)
2-MeTHF (0.02 M), 25 °C, 90 min
Blue LED
440 nm, 40
W
2.0 equiv
O
O
O
O
O
Method
A
1
2
Entry Variation from standard conditions
Yield
lactone
Ketone
recovery
A1
None
81%
14%
A2
None
74%
13%
A3
None
75%
15%
A4
None
73%
14%
Entry 1,
Table 1
A
None
76±3%
14±1%
A5
No light
5%
89%
A6
No light
4%
93%
Entry 2,
Table 1
A
No light
4±1%
91±2%
A7
No Sm
<1%
102%
A8
No Sm
<1%
100%
Entry 3,
Table 1
A
No Sm
<1%
101±1%
A9
SmOTf
3
(10 mol%) MgI
2
(50 mol%) instead of SmI
2
59%
41%
A10
SmOTf
3
(10 mol%) MgI
2
(50 mol%) instead of SmI
2
60%
42%
Entry 4,
Table 1
A
SmOTf
3
(10 mol%) MgI
2
(50 mol%) instead of SmI
2
,
60±1%
41±1%
A11
GdOTf
3
(10 mol%) MgI
2
(50 mol%) instead of SmI
2
,
<1%
101%
A12
GdOTf
3
(10 mol%) MgI
2
(50 mol%) instead of SmI
2
,
<1%
95%
Entry 5,
Table 1
A
GdOTf
3
(10 mol%) MgI
2
(50 mol%) instead of SmI
2
<1%
98±3%
A13
2 equiv pyr
72%
8
A14
2 equiv pyr
72%
10
Entry 6,
Table 1
A
2 equiv pyr
72±1%
9±1%
A15
2 equiv Et
3
N
6%
79%
A16
2 equiv Et
3
N
5%
72%
Entry 8,
Table 1
A
2 equiv Et
3
N
5±1%
75±4%
A17
phenH
2
instead of HEH
2
<1%
37%
A18
phenH
2
instead of HEH
2
<1%
39%
Entry 9,
Table 1
A
phenH
2
instead of HEH
2
<1%
38±1%
A19
15 min reaction time
29%
63%
A20
15 min reaction time
29%
65%
Entry 10,
Table 1
A
15 min reaction time
29±1%
64±1%
A21
Ethyl acrylate instead of phenyl acrylate
36%
46%
A22
Ethyl acrylate instead of phenyl acrylate
25%
52%
Entry 11,
Table 1A
Ethyl acrylate instead of phenyl acrylate
31±5%
49±3%
S6
Entry
Variation
Yield
lactone
Ketone
recovery
B1
None
87%
7%
B2
None
89%
6%
B3
None
89%
5%
B4
None
89%
4%
Entry 1,
Table 1B
None
88.6±0.8%
5.7±1.1%
B5
No light
4%
94%
B6
No light
4%
92%
Entry 2,
Table 1B
No light
4±1%
93±1%
B7
No Sm
<1%
89%
B8
No Sm
<1%
82%
Entry 3,
Table 1B
No Sm
0%
86±3%
B9
SmOTf
3
(10 mol%) MgI
2
(50 mol%) instead of SmI
2
85%
14%
B10
SmOTf
3
(10 mol%) MgI
2
(50 mol%) instead of SmI
2
84%
13%
Entry 4,
Table 1B
SmOTf
3
(10 mol%) MgI
2
(50 mol%) instead of SmI
2
85±1%
14±1%
B11
GdOTf
3
(10 mol%) MgI
2
(50 mol%) instead of SmI
2
6%
92%
B12
GdOTf
3
(10 mol%) MgI
2
(50 mol%) instead of SmI
2
6%
85%
Entry 5,
Table 1B
GdOTf
3
(10 mol%) MgI
2
(50 mol%) instead of SmI
2
6±1%
88±4%
B13
No
base
84%
8%
B14
No base
80%
8%
Entry 7,
Table 1B
No base
82±2%
8±1%
B15
Et
3
N instead of pyridine
13%
69%
B16
Et
3
N instead of pyridine
17%
73%
Entry 8,
Table 1B
Et
3
N instead of pyridine
15±2%
71±2%
B17
phenH
2
instead of HEH
2
78%
0
B18
phenH
2
instead of HEH
2
76%
2
Entry 9,
Table 1B
phenH
2
instead of HEH
2
77±1%
1±1%
B19
15 min reaction time
57%
43%
B20
15 min reaction time
66%
32%
Entry 10,
Table 1B
15 min reaction time
61±4%
38±6%
B19
Ethyl acrylate instead of phenyl
acrylate
59%
11%
B20
Ethyl acrylate instead of phenyl acrylate
56%
12%
Entry 11,
Table 1B
Ethyl acrylate instead of phenyl acrylate
58±2%
12±1%
S7
S2.2.1 Quantification of additional organic products under standard conditions
While the work-up and detection method should account for ~100% of the ketone starting material, the
limited solubility of HEH
2
in Et
2
O and CDCl
3
and the low boiling point of phenyl acrylate result in some
additional error in these product yields. Figure S1 presents approximate yields as integrated against a
TMB standard for a reaction where care was taken to evaporate minimal phenyl acrylate.
Figure S1.
Approximate yields of additional products under conditions without and with Iridium.
S8
Figure S2.
Typical setup for catalytic experiments. Lights are turned off for clarity.
S9
Figure S3.
1
H NMR (CDCl
3
7.26 ppm) of a typical crude reaction mixture reacting
1
with phenyl acrylate
to produce
2
with key products/starting materials highlighted as indicated.
S10
Figure S4.
Comparison of
1
H NMR of typical reaction spectra with authentic lactone product.
1
H NMR
(400 MHz, CDCl
3
):
δ 4.00 – 3.90 (m, 4H), 2.60 (t,
J
= 8.5 Hz, 2H), 2.04 (t,
J
= 8.5 Hz, 2H), 1.97 – 1.88
(m, 4H), 1.82 (ddd,
J
= 17.5, 10.9, 4.0 Hz, 2H), 1.70 – 1.62 (m, 2H).
S11
Figure S5.
1
H NMR (CDCl
3
7.26 ppm) of a typical crude reaction mixture reacting
cyclohexanone
with
phenyl acrylate to produce
3
with key products/starting materials highlighted as indicated. The lactone
product
3
matched previous reports.
5
S12
Figure S6.
1
H NMR (CDCl
3
7.26 ppm) of a typical crude reaction mixture reacting
acetophenone
with
phenyl acrylate to produce
4
with key products/starting materials highlighted as indicated. The lactone
product
4
matched previous reports.
5
S13
Figure S6.
1
H NMR (CDCl
3
7.26 ppm) of a typical crude reaction mixture reacting
4-
trifluoromethylacetophenone
with phenyl acrylate to produce
5
with key products/starting materials
highlighted as indicated. The lactone product
5
matched previous reports.
5
S14
Figure S7.
1
H NMR (CDCl
3
7.26 ppm) of a typical crude reaction mixture reacting
acetophenone
with
tert
-butyl acrylate to produce
6
with key products/starting materials highlighted as indicated.
S15
Figure S8.
1
H NMR (CDCl
3
7.26 ppm) of a typical crude reaction mixture reacting
acetophenone
with
tert
-butyl acrylate to produce
4
with key products/starting materials highlighted as indicated. The lactone
product
4
matched previous reports.
5
S16
S2.3 Additional catalysis tables
Table S2.
Additional catalytic experiments of ketone-acrylate coupling.
S17
Table S3.
Yields for pinacol coupled products in selected aryl ketone cross-coupling reactions.
Table S4.
Additional screening interrogating the effect of quencher (HEH
2
, MeacrH, phenH
2,
or Et
3
N) on
catalysis. All results with error bars represent the average and standard deviation of a minimum of two
experiments.
S18
Table S5.
Additional screening interrogating the effects of additives (MgI
2
or [PyrH]TFSI) on catalysis.
Table S6.
Additional screening interrogating the effect of HEH
2
loading on catalysis. All results with
error bars represent the average and standard deviation of a minimum of two experiments.
S19
S3 UV-vis experiments
S3.1 UV-vis detection of Sm interaction with dihydropyridines
Figure S9.
Comparison of UV-vis traces (in a 1 mm path-length cuvette) of SmI
2
(2 mM) + ketone (20
mM) + acrylate (40 mM) (yellow trace,
in situ
forms colorless Sm
III
I
2
(OPh)); HEH
2
(80 mM) + ketone
(20 mM) + acrylate (40 mM) (red trace); and SmI
2
(2 mM) + HEH
2
(80 mM) + ketone (20 mM) +
acrylate (40 mM) (blue trace). All spectra collected in 2-MeTHF. Observed red-shift of the HEH
2
absorption in the presence of Sm
III
is consistent with interaction between species
.
Figure S10.
Comparison of UV-vis traces (in a 1 mm path-length cuvette) of SmI
2
(2 mM) + ketone (20
mM) + acrylate (40 mM) (yellow trace,
in situ
forms colorless Sm
III
I
2
(OPh)); phenH
2
(80 mM) + ketone
(20 mM) + acrylate (40 mM) (red trace); and SmI
2
(2 mM) + phenH
2
(80 mM) + ketone (20 mM) +
acrylate (40 mM) (blue dashed trace). All spectra collected in 2-MeTHF. Overlay suggests little to no
interaction between Sm
III
and phenH
2
.
S20
Figure S11.
Comparison of UV-vis traces (in a 1 cm path-length cuvette) of Sm(O
i
Pr)
3
(2 mM),
n
Hep
4
NI
(6 mM), and HTFSI (3 mM) (yellow trace,
in situ
forms colorless Sm
III
I
2
(O
i
Pr)); HEH
2
(60 mM) (red
trace); and Sm(O
i
Pr)
3
(2 mM),
n
Hep
4
NI (6 mM), HTFSI (3 mM), and HEH
2
(60 mM) (blue trace). All
spectra collected in THF. The observed red-shift suggests interaction between Sm
III
and HEH
2
.
Figure S12.
Comparison of UV-vis traces (in a 1 mm path-length cuvette) of Sm(O
i
Pr)
3
(2 mM),
n
Hep
4
NI
(6 mM), [LutH]TFSI (3 mM) (yellow trace,
in situ
forms colorless Sm
III
I
2
(O
i
Pr)); phenH
2
(60 mM) (red
trace); and Sm(O
i
Pr)
3
(2 mM),
n
Hep
4
NI (6 mM), [LutH]TFSI (3 mM), and phenH
2
(60 mM) (dashed blue
trace). All spectra collected in THF. Overlay suggests little to no interaction between Sm
III
and phenH
2
.
S21
Figure S13.
Comparison of UV-vis traces (in a 1 cm path-length cuvette) of Sm(O
i
Pr)
3
(2 mM),
n
Hep
4
NI
(6 mM), [LutH]TFSI (3 mM) (yellow trace,
in situ
forms colorless Sm
III
I
2
(O
i
Pr)); HEH
2
(60 mM) (red
trace); and Sm(O
i
Pr)
3
(2 mM),
n
Hep
4
NI (6 mM), [LutH]TFSI (3 mM), and HEH
2
(60 mM) (blue trace).
All spectra collected in THF. The observed red-shift suggests interaction between Sm
III
and HEH
2
.
Figure S14.
Comparison of UV-vis traces (in a 1 cm path-length cuvette) of Sm(O
i
Pr)
3
(2 mM),
n
Hep
4
NI
(6 mM), (yellow trace,
in situ
is still colorless Sm
III
(O
i
Pr)
3
); HEH
2
(60 mM) (red trace); and Sm(O
i
Pr)
3
(2
mM),
n
Hep
4
NI (6 mM), and HEH
2
(60 mM) (blue trace). All spectra collected in THF. The observed red-
shift suggests interaction between Sm
III
and HEH
2
.
S22
Figure S15.
Titration of Sm(OTf)
3
(0 to 5 mM, from red to blue trace) into a solution of HEH
2
(100 mM)
in THF. Substantial red-shift observed upon titration of Sm(OTf)
3
.
S23
S3.2 Sm
II
photogeneration experiments
S3.2.1 General procedure for Sm
II
photogeneration experiments
A fresh 5 mM stock solution of SmI
2
in THF is prepared immediately before use. SmI
3
is prepared by
titrating this 5 mM THF solution of SmI
2
with I
2
until the characteristic blue color of SmI
2
disappears.
An aliquot of the resulting SmI
3
solution (1 mL, 0.005 mmol) is added to a vial (1 mL) containing
reductant (0.15 mmol, 30 equiv) and an additional 1 mL of THF, and this solution is transferred to a 1 cm
path-length cuvette. 100 uL of a stock solution of photocatalyst is added to the cuvette, followed by base
(0.15 mmol, 30 equiv), an additional 0.5 mL THF and any alternative ligands (e.g.
n
Bu
4
NBr, BINAPO) as
indicated.
S3.2.2 General procedure for Sm
II
(HMPA)
4
photogeneration experiments
For the Sm
II
(HMPA)
2+
generation, 4 equiv HMPA was added to the initial SmI
2
solution prior to
oxidation by I
2
. The rest of the procedure was identical following
S3.2.1.
S24
S3.2.3 Summary of Sm
II
photogeneration experiments
The Sm
II
photogeneration experiments (S3.2.4) are summarized in Table S7.
Table S7.
Summary of conditions and yields for photodriven Sm
III
reductions. Approximate yield of Sm
II
is determined based on the spectrum of the preparation of additive + SmI
2
.
Sm
III
+ additives
Photocat. Conditions (THF and 25 °C unless otherwise
specified)
Sm
II
formation
SmI
3
(2 mM)
-
HEH
2
(60 mM), Lut (60 mM), H150-Blue LED
34 W
~30%
SmI
3
(2 mM)
-
HEH
2
(60 mM),
H160
-
440 nm LED
0%
Sm(O
i
Pr)
3
(2 mM),
n
Hep
4
NI (6 mM),
H
TFSI (3 mM)
-
HEH
2
(60 mM), H160-440 nm LED 40 W
~15%
Sm(O
i
Pr)
3
(2 mM),
n
Hep
4
NI
(6 mM)
-
HEH
2
(60 mM), H160-440 nm LED 40 W
0%
SmI
3
(2 mM)
[Ir]PF
6
(0.2
mM)
HEH
2
(60 mM), Lut (60 mM),
H160
-
440 nm LED 40 W
80%
SmI
3
(2 mM)
[Ir]PF
6
(0.2
mM)
HEH
2
(60 mM), H160-440 nm LED 40 W
10%
Sm(O
i
Pr)
3
(2 mM),
n
Hep
4
NI (6 mM),
[LutH]TFSI (3 mM)
[Ir]PF
6
(0.2
mM)
HEH
2
(60 mM), Lut (60 mM),
H160-440 nm LED 40 W
30%
SmI
3
(2 mM),
HO(CH
2
)
2
OH (2 mM)
[Ir]PF
6
(1
mM)
HEH
2
(60 mM), pyridine (60 mM), THF, 0 °C,
H160
-
440 nm LED 40 W
15%
SmI
3
(2 mM),
MeO((CH
2
)
2
O)
3
H (2
mM)
[Ir]PF
6
(1
mM)
HEH
2
(60 mM), pyridine (60 mM), THF, 0 °C,
H160-440 nm LED 40 W
5%
SmI
3
(2 mM), L* (2.2
mM)
[Ir]PF
6
(0.2
mM)
HEH
2
(60 mM), H160-440 nm LED 40 W
10%
SmI
3
(2 mM),
n
Bu
4
N
Br (20 mM)
-
HEH
2
(60 mM), Lut (60 mM),
H160
-
440 nm LED 40 W
0%
SmI
3
(2 mM), HMPA
(8 mM)
-
HEH
2
(60 mM), Lut (60 mM),
H160
-
440 nm LED 40 W
0%
SmI
3
(2 mM),
n
Bu
4
N
Br (20 mM)
[Ir]PF
6
(0.2
mM)
Et
3
N (60 mM), H160-440 nm LED 40 W
0%
SmI
3
(2 mM), HMPA
(8 mM)
[Ir]PF
6
(0.2
mM)
Et
3
N (60 mM), H160-440 nm LED 40 W
0%
SmI
3
(2 mM),
BINAPO (2.2 mM)
[Ir]PF
6
(0.2
mM)
Et
3
N (60 mM), H160-440 nm LED 40 W
0%
SmI
3
(2 mM)
3DPA2FBN
(0.05 mM)
acrH
2
(60 mM) Et
3
N (60 mM),
H150
-
Blue LED 34 W
20%
SmI
3
(2 mM),
n
Bu
4
N
Br (20 mM)
3DPA2FBN
(0.05 mM)
acrH
2
(60 mM) Et
3
N (60 mM),
H160
-
440 nm LED 40 W
40%
SmI
3
(2 mM), HMPA
(8 mM)
3DPA2FBN
(0.05 mM)
acrH
2
(60 mM) Et
3
N (60 mM),
H150
-
Blue LED 34 W
10%
SmI
3
(2 mM),
BINAPO (2.2 mM)
3DPA2FBN
(0.05 mM)
acrH
2
(60 mM) Et
3
N (60 mM),
H160
-
440 nm LED 40 W
10%
S25
S3.2.4 Sm
II
photogeneration experiments
Figure S16.
Photogeneration of SmI
2
from a THF solution of SmI
3
(2 mM), HEH
2
(60 mM) and Lut (60
mM) on irradiation with H150-Blue LED; t = 0 (red trace); t =120 min (blue trace). Maximum intensity
suggests about 30% conversion to SmI
2
.
S26
Figure S17.
Attempted photogeneration of SmI
2
from a THF solution of SmI
3
(2 mM) and HEH
2
(60
mM) on irradiation with H160-440 nm; t = 0 (red trace); t =60 min (blue trace). No SmI
2
is observed even
on extended irradiation.
S27
Figure S18.
Photogeneration of SmI
2
from a THF solution of Sm(O
i
Pr)
3
(2 mM),
n
Hep
4
NI (6 mM),
HTFSI (3 mM), and HEH
2
(60 mM) on irradiation with H160 440 nm; t = 0 (red trace); t =20 min (lowest
intensity grey trace), 80 minutes (blue trace), 180 minutes (yellow dashed trace) irradiation. Maximum
intensity suggests about 15% conversion to SmI
2
.
S28
Figure S19.
Attempted photogeneration of SmI
2
from a THF solution of Sm(O
i
Pr)
3
(2 mM),
n
Hep
4
NI (6
mM), and HEH
2
(60 mM) on irradiation with H160-440 nm LED; t = 0 (red trace); t =40 min (blue
dashed trace). No SmI
2
is observed even on extended irradiation.
S29
0
0.2
0.4
0.6
0.8
1
300
500
700
Absorbance
Wavelength (nm)
Figure S20.
Photogeneration of SmI
2
from a THF solution of SmI
3
(2 mM), HEH
2
(60 mM), and Lut (60
mM) with [
Ir
]PF
6
(0.2 mM) as photosensitizer on irradiation with H160-440 nm LED over t = 0 (red
trace) to t = 2 min (blue trace). Maximum intensity suggests about 80% conversion to SmI
2
.
S30
0
0.2
0.4
0.6
0.8
1
300
500
700
Absorbance
Wavelength (nm)
Figure S21.
Photogeneration of SmI
2
from a THF solution of SmI
3
(2 mM) and HEH
2
(60 mM) with
[
Ir
]PF
6
(0.2 mM) as photosensitizer in the absence of base on irradiation with H160-440 nm LED over t =
2 min (red trace), t = 6 min (yellow trace), to t = 16 min (dark blue trace). Maximum intensity suggests
<10% conversion to SmI
2
over prolonged irradiation; the absence of observed SmI
2
at 2 min (compared to
80% SmI
2
generation at the same time point in the presence of Lut) suggests that Lut accelerates SmI
2
photogeneration under these conditions.