S
1
A Terminal Fe
III
-
Oxo in a Tetranuclear Cluster: Effects of
Distal
Metal Centers on
Structure
and Reactivity
Christopher J. Reed and Theodor Agapie*
Division of Chemistry and Chemical Engineering, California Institute of Technology
Pasadena, Califor
nia 91125, United States, Email: agapie@caltech.edu
Supporting Information
S
2
Table of Contents
Experimental Procedures
................................
................................
................................
...........
S
5
Figure S1.
1
H NMR spectrum (300 MHz) of 2
-
tert
-
butyl
-
isoxazolium tetrafluoroborate
.........
S1
3
Figure S2.
1
H NMR spectrum (400 MHz) of
N
-
t
ert
-
butyl
-
1
H
-
pyrazol
-
3
-
amine
.......................
S1
3
Figure S3.
13
C{
1
H} NMR spectrum (100 MHz) of
N
-
tert
-
butyl
-
1
H
-
pyrazol
-
3
-
amine
.............
S1
4
Figure S4.
1
H NMR spectrum (300 MHz) of
LFe
3
O(PzNHtBu)
3
Fe(OH)
(
1
)
...........................
S1
4
Figure S5.
1
H NMR spectrum (300 MHz) of [
LFe
3
O(PzNHtBu)
3
Fe(OH)
][OTf] (
2
)
...............
S1
5
Figure S6.
1
H NMR spectrum (300 MHz) of [
LFe
3
O(PzNHtBu)
3
Fe(OH)
][OTf]
2
(
3
)
..............
S1
5
Figure S7.
1
H NMR spectrum (300 MHz) of [
LFe
3
O(PzNHtBu)
3
Fe(OH)
][OTf]
3
(
4
)
..............
S1
6
Figure S8.
1
H NMR spectrum (300 MHz) of
LFe
3
O(PzNHtBu)
3
Fe(O)
(
5
)
..............................
S1
6
Figure S9.
1
H NMR spectrum
(
4
00 MHz) of [
LFe
3
O(PzNHtBu)
3
Fe(O)
][OTf] (
6
)
..................
S1
7
Figure S10.
1
H NMR spectrum (300 MHz) of [
LFe
3
O(PzNHtBu)
3
Fe(O)
][OTf]
2
(
7
)
...............
S1
7
Figure S11.
T
itration of
2
with Ph
3
PCH
2
via
1
H and
31
P NMR
................................
.................
S1
8
Table S1.
p
K
a
determination of
2
................................
................................
...............................
S1
8
Figure S12.
Titration of
2
w
ith
tert
-
butylimino
-
tri(pyrrolidino)phosphorene via
1
H NMR
......
S1
9
Table S2.
p
K
a
determination of
3
................................
................................
...............................
S1
9
Figure S13.
1
H NMR spectra (400 MHz) of
5
with phenols, fluorene, and
trimethylphosphine
................................
................................
................................
.....................
S
20
Figure S14.
1
H NMR spectra (400 MHz) of
6
with phenols and trim
ethylphosphine
...............
S
20
Figure S15.
1
H NMR spectra (400 MHz) of
6
with fluorene
................................
.....................
S2
1
Figure S16.
1
H NMR spectra (
3
00 MHz) of
7
with phenols and trimethylphosphine
...............
S2
1
Figure S17.
1
H NMR spectra (400 MHz) of
7
with 9,10
-
dihydroanthracene and fluorene
.......
S2
2
Product
analysis of oxidation reactions between 5
–
7 and 9,10
-
dihydroanthracene,
fluorene, and 2,4,6
-
tri
-
tert
-
butylphenol
................................
................................
..................
S23
Table S3.
Yields of PCET reactions between 9,10
-
dihydroanthracene or fluorene with the Fe
-
oxo clusters
5
–
7
................................
................................
................................
........................
S23
18
-
O
xygen
i
ncorporation
into the
t
ert
-
butyl
a
mino
p
yrazolate
b
ridged
t
etranuclear Fe
c
lusters
................................
................................
................................
................................
.......
S2
4
Figure S1
8
.
ESI
-
MS spectra of
2
and
2
-
18
O
................................
................................
..............
S2
4
Oxygen
a
tom
t
ransfer
s
tudies of
o
xidized Fe
4
-
o
xo
c
luster with
t
rimethylphosphine
.........
S2
5
Figure S1
9
.
31
P NMR spectra (120 MHz; right) of [
LF
e
3
O(PzNHtBu)
3
Fe(O)
][OTf] (
6
) with
[Fc][OTf] and 20 equivalents
trimethylphosphine
................................
................................
.....
S2
5
Figure S20
.
GC/MS chromatographs of the reaction between
18
O
-
“LFe
3
OPzNHtBu)
3
Fe(O)
2+
”
and trimethylphosphine
................................
................................
................................
...............
S2
6
Figure S2
1
.
UV
-
Vis absorbance spectra of
LFe
3
O(PzNHtBu)
3
Fe
(O
H
)
(
1
)
..............................
S2
7
Figure S2
2
.
UV
-
Vis absorbance spectra of [
LFe
3
O(PzNHtBu)
3
Fe(O
H
)
][OTf] (
2
)
..................
S2
7
Figure S2
3
.
UV
-
Vis absorbance spectra of [
LFe
3
O(PzNHtBu)
3
Fe(O
H
)
][OTf]
2
(
3
)
.................
S2
8
Figure S2
4
.
UV
-
Vis absorbance spectra of [
LFe
3
O(PzNHtBu)
3
Fe(O
H
)
][OTf]
3
(
4
)
.................
S2
8
Figure
S2
5
.
UV
-
Vis absorbance spectra of
LFe
3
O(PzNHtBu)
3
Fe(O
) (
5
)
................................
.
S2
9
Figure S26.
UV
-
Vis absorbance spectra of [
LFe
3
O(PzNHtBu)
3
Fe(O
)][OTf] (
6
)
.....................
S2
9
Figure S27.
UV
-
Vis absorbance spectra of [
LFe
3
O(PzNHtBu)
3
Fe(O
)][OTf]
2
(
7
)
....................
S
30
Table S4.
Second order rate constants
for
5
and various organic C
–
H bonds
...........................
S
3
1
Figure S2
8
.
Plots normalized k
2
versus BDE and p
K
a
for PCET reactions with
5
....................
S
3
1
Figure S2
9
.
UV
-
Vis absorbance spectra of
LFe
3
O(PzNHtBu)
3
Fe(O)
(
5
) and xanthene
...........
S3
2
S
3
Figure S
30
. Kinetics data for the reaction between
L
Fe
3
O(PzNHtBu)
3
Fe(O
) (
5
) and
xanthene
................................
................................
................................
................................
......
S3
2
Figure S3
1
.
UV
-
Vis absorbance and kinetics data for the reaction between
LFe
3
O(PzNHtBu)
3
Fe(O
) (
5
) and 1,4
-
cyclohexadiene
................................
................................
S3
3
Figure S
3
2
.
UV
-
Vis absorbance spectra of
LFe
3
O(PzNHtBu)
3
Fe(O)
(
5
) and 9,10
-
dihydroanthrace
ne
................................
................................
................................
.......................
S3
3
Figure S
3
3
Kinetics data for the reaction between
LFe
3
O(PzNHtBu)
3
Fe(O
) (
5
) and 9,10
-
dihydroanthracene
................................
................................
................................
.......................
S
3
4
Figure
S3
4
Kinetics data for the reaction between
LFe
3
O(PzNHtBu)
3
Fe(O
) (
5
) and
d
4
-
9,10
-
dihydroanthracene
................................
................................
................................
.......................
S
3
4
Figure S3
5
.
UV
-
Vis absorbance and
kinetics data for the reaction between
LFe
3
O(PzNHtBu)
3
Fe(O
) (
5
) and triphenylmethane
................................
................................
...
S3
5
Figure S3
6
.
UV
-
Vis absorbance and kinetics data for the reaction between
LFe
3
O(PzNHtBu)
3
Fe(O
) (
5
) and fluorene
................................
................................
..................
S3
5
Figure S
3
7
.
Cyclic voltammetry of [LFe
3
O(PzNHtBu)
3
Fe
(OH)][OTf] (
2
)
in THF
..................
S3
6
Figure S
3
8
.
Cyclic voltammetry of [LFe
3
O(PzNHtBu)
3
Fe(OH)][OTf] (
2
)
in THF at various scan
rates
................................
................................
................................
................................
.............
S3
6
Figure S3
9
.
Cyclic voltammetry of LFe
3
O(PzNHtBu)
3
Fe(O) (
5
) in THF
................................
.
S3
7
Figure S
40
.
Cyclic voltammetry of LFe
3
O(PzNHtBu)
3
Fe(O) (
5
) i
n THF at various scan rates
................................
................................
................................
................................
.....................
S3
7
M
ö
ssbauer simulation details
................................
................................
................................
...
S3
8
Simulation details for LFe
3
O(PzNHtBu)
3
Fe(OH) (1)
................................
............................
S3
8
Figure S4
3
.
Zero applied field M
ö
ssbauer spectrum of
1
................................
..........................
S3
9
Simulation details for [LFe
3
O(PzNHtBu)
3
Fe(OH)][OTf] (2)
................................
................
S
3
9
Figure S
4
6
.
Zero a
pplied field M
ö
ssbauer spectrum of
2
................................
..........................
S
4
1
Simulation details for [LFe
3
O(PzNHtBu)
3
Fe(OH)][OTf]
2
(3)
................................
..............
S
4
1
Figure S4
7
.
Zero applied field M
ö
ssbauer spectrum of
3
................................
..........................
S
4
2
Simulation details for [LFe
3
O(PzNHtBu)
3
Fe(OH)][OTf]
3
(4)
................................
..............
S
4
2
Figure S4
8
.
Zero applied field M
ö
s
sbauer spectrum of
4
................................
..........................
S
4
2
Simulation details for LFe
3
O(PzNHtBu)
3
Fe(O) (5)
................................
...............................
S
4
3
Figure S5
2
.
Zero applied field M
ö
ssbauer spectrum of
5
................................
..........................
S
4
4
Simulation details for [LFe
3
O(PzNHtBu)
3
Fe(O)][OTf] (6)
................................
...................
S
4
4
Figure S
5
5
.
Zero applied field M
ö
ssbauer spectrum of
6
................................
..........................
S4
6
Si
mulation details for [LFe
3
O(PzNHtBu)
3
Fe(O)][OTf]
2
(7)
................................
.................
S4
6
Figure S5
7
.
Zero applied field M
ö
ssbauer spectrum of
7
................................
..........................
S4
7
Figure S5
8
.
1
H NMR spectrum (300 MHz) of M
ӧ
ssbauer sample of
7
................................
.....
S4
8
Figure S5
9
.
Crystal structure of LFe
3
O(PzNHtBu)
3
Fe(OH) (
1
)
................................
................
S4
9
Figure S6
0
.
Crystal structure and special refinement details of [LFe
3
O(PzNHtBu)
3
Fe(OH)][PF
6
]
(
2
-
PF
6
)
................................
................................
................................
................................
........
S
50
Figure S6
1
.
Crystal structure and special refinement details of
[LFe
3
O(PzNHtBu)
3
Fe(OH)][OTf]
2
(
3
)
................................
................................
.......................
S
5
1
Figure S
6
2
.
Crystal structure and special refinement detai
ls of LFe
3
O(PzNHtBu)
3
Fe(O) (
5
)
................................
................................
................................
................................
.....................
S
5
2
Figure S
6
3
.
Crystal structure and special refinement details of [LFe
3
O(PzNHtBu)
3
Fe(O)][OTf]
(
6
)
................................
................................
................................
................................
................
S
5
3
S
4
Table S
5
.
Selected bond parameters for structurally characterized compounds
1
-
3
,
5
, and
6
................................
................................
................................
................................
.....................
S
5
4
Table S
6
. Crystal and ref
inement data for complexes
1
-
3
,
5
, and
6
................................
..........
S
5
5
References
................................
................................
................................
................................
..
S5
6
S
5
Experimental Procedures
General Considerations
All reactions were performed at room temperature in an N
2
-
filled M. Braun glovebox or using
standard Schlenk techniques unless otherwise specified
; reactions with KOH were performed in
an
N
2
-
filled
VAC
wetbox.
Glassware was oven dried at 140 ºC for at least 2 h prior to use, and
allowed to cool under vacuum.
LFe
3
(OAc)(OTf)
2
,
1
iodosylbenzene,
2
benzyl potassi
um,
3
Fe(OTf)
2
• 2 MeCN,
4
ferrocenium trifluo
romethane sulfonate ([Fc][OTf]),
5
and
Ph
3
PCH
2
6
were prepared
according to literature procedures.
N
-
tert
-
butyl
-
1
H
-
pyrazol
-
5
-
a
mine (HPzNHtBu)
was prepared
according to a modified literature procedure.
7
18
-
oxygen labeled potassium hydroxide (K
18
OH)
was prepared by quenching a tetrahydrofuran solution of benzyl potassium (less than 1 mmol) with
H
2
18
O, an
d drying the resulting white suspension under vacuum.
Tetrahydrofuran,
CH
2
Cl
2
, diethyl
ether, benzene
, toluene
, acetonitrile, hexanes, and pentane were dried by sparging with nitrogen
for at least 15 minutes, then passing through a column of activated A2 a
lumina under positive N
2
pressure.
1
H spectra were recorded o
n a Varian 300 MHz spectrometer;
13
C NMR spectra were
recorded on a Varian 500 MHz spectrometer.
1
H and
31
P NMR spectra in THF/C
6
D
6
were
recorded
on a Varian 500 MHz spectrometer
using solvent su
ppression protocols
.
NMR spectra collected at
low temperature were recorded on a Bruker 500 MHz spectrometer.
CD
3
CN, C
6
D
6
, and
CD
2
Cl
2
was purchased from Cambridge Isotope Laboratories, dried over calcium hydride, degassed by
three freeze
-
pump
-
thaw cycles,
and vacuum transferred prior to use.
Physical Methods
M
össbauer measurements
. Zero
applied
field
57
Fe Mossbauer spectra were recorded at 80 K in
constant acceleration mode on a spectrometer from See Co (Edina, MN) equipped with an SVT
-
S
6
400 cryostat (Janis,
Wilmington, WA). The isomer shifts are relative to the centroid of an α
-
Fe foil
signal at room temperature. Samples were prepared by mixing polycrystalline material (20 mg)
with boron nitride in a cup fitted with screw cap or freezing a concentrated aceto
nitrile solution in
the cup. The data were fit to Lorentzian lineshapes using WMOSS (www.wmoss.org).
Electrochemical measurements
. CVs and SWVs were recorded with a Pine Instrument Company
AFCBP1 biopotentiostat with the AfterMath software package. All mea
surements were performed
in a three electrode cell, which consisted of glassy carbon (working; ø = 3.0 mm), silver wire
(counter) and bare platinum wire (reference), in a N
2
filled M. Braun glovebox at RT. Dry
acetonitrile
or
tetrahydrofuran
that contained
~
100
mM [Bu
4
N][PF
6
]
was used as the electrolyte
solution. The ferrocene/ferrocinium (Fc/Fc
+
) redox wave was used as an internal standard for all
measurements.
X
-
ray crystallography
. X
-
ray diffraction data was collected at 100 K on a Bruker PHOTON100
CMOS
based diffractometer (microfocus sealed X
-
ray tube, Mo Kα (λ) = 0.71073 Å or Cu Kα (λ)
= 1.54178 Å). All manipulations, including data collection, integration, and scaling, were carried
out using the Bruker APEXII software. Absorption corrections were appl
ied using SADABS.
Structures were solved by direct methods using XS (incorporated into SHELXTL) and refined by
using ShelXL least squares on Olex2
-
1.2.7 to convergence. All non
-
hydrogen atoms were refined
using anisotropic displacement parameters. Hydrogen
atoms were placed in idealized positions
and were refined using a riding model. Due to the size of the compounds (
1
–
3
,
5
, and
6
), most
crystals included solvent
-
accessible voids that contained disordered solvent. In most cases the
solvent could be model
ed satisfactorily.
S
7
Synthetic Procedures
Synthesis of 2
-
tert
-
butyl
-
isoxazolium tetrafluoroborate.
25 mL isoxazole
(
0.4 mol
) was
combined with 37 mL
tert
-
butanol
(
0.4 mol
) in a 500 mL roundbottom flask.
This was cooled to
-
20
°
C with an ice/sodium chlorid
e bath while 160 mL tetrafluoroboric acid diethyl ether complex
(1.2 mol)
was added dropwise over 1 hour. After the addition was complete, the reaction was
warmed to room temperature and stirred for 4 hours. Then, 100 mL Et
2
O and 50 mL THF was
added to the
reaction and cooled to
-
20
°
C; the resulting precipitat
e was collected on a glass frit,
washed three times with 200 mL Et
2
O and dried under reduced pressure. 60 g of 2
-
tert
-
butyl
-
isoxazolium tetrafluoroborate (72% yield) can be obtained this way; another
6 g can be obtained
by cooling the filtrate and Et
2
O washings to
-
20
°
C overnight and collecting the resulting crystals
(79% overall yield).
1
H NMR (300 MHz, (CD
3
)
2
CO):
δ
1.90
(s, 9H)
, 7.46
(s, 1H)
, 9.55
(s, 1H)
,
9.77
(s, 1H)
ppm.
Synthesis of
N
-
tert
-
butyl
-
1
H
-
pyrazol
-
3
-
amine
(
HPzNHtBu
)
.
This procedure was adapted from
a report describing the synthesis of
tert
-
butyl substituted 3
-
aminopyrazoles.
7
10
.0
g of
2
-
tert
-
butyl
-
isox
a
zolium tetrafluoroborate
(4
7
mmol)
was suspended in 100 mL EtOH in a 250 mL
roundbottom flask and cooled with an ice bath to 0
°
C. A solution of 4.56 mL hydrazine
monohydrate
(9
4
mmol)
in 20 mL EtOH was added dropwise to the c
ooled flask. After complete
addition, the reaction was warmed to room temperature and stirred for 30 minutes. EtOH was
removed via
rotary
evaporation and an aqueous work up was performed with 100 mL H
2
O and 3
x 100mL CH
2
Cl
2
, collecting the organic layers.
The combined organic fractions were dried with
Na
2
SO
4
, filtered, and dried to yield an orange oil. The crude product was purified via Kugelrohr
distillation
under vacuum at 90
°
C. The distillate was recrystallized with Et
2
O and the resulting
white
solid wa
s sublimed
under vacuum at 60
°
C
to yield
1.6
g of HPzNHtBu (
24
% yield).
1
H
S
8
NMR (400 MHz, CD
2
Cl
2
):
δ
1.27 (s, 9H), 3.61 (br), 5.71 (d, 1H), 7.34 (d, 1H), 9.75 (br) ppm.
13
C{
1
H} NMR
(100 MHz, CD
2
Cl
2
):
53.28, 75.11, 118.60, 154.26 ppm
(a signal for the
tert
-
butyl
quaternary carbon was likely not observed)
.
Anal. calcd. (%) for C
7
H
13
N
3
: C, 60.40; H, 9.41; N,
30.19. Found: C, 60.75; H, 9.37; N, 30.20.
Synthesis of
potassium
N
-
tert
-
butyl
-
1
H
-
pyrazol
-
3
-
amine
-
ate
(
K
PzNHtBu)
.
1.25 g
N
-
tert
-
butyl
-
1
H
-
pyrazol
-
3
-
amine
(
9 mmol)
was dissolved in 5 mL THF. A THF solution of 1.17 g benzyl
potassium (9 mmol) was added dropwise, while stirring. After 30 minutes, the reaction was
concentrated to 5 mL, and the precipitate was collected via filtration. The precipitate was washed
with Et
2
O and dried under vacuum to yield 1.2 g KPzNHtBu as a white solid (75% yield).
Anal.
calcd. (%) for C
7
H
1
2
K
N
3
: C, 47.42; H, 6.82; N, 23.70. Found: C, 47.50; H, 6.83; N, 23.61.
Synthesis of LFe
3
O(PzNHtBu)
3
Fe(OH)
(1)
.
1.287
g (
0.93
mmol)
LFe
3
(OAc)(OTf
)
2
was
suspended in THF and froze in a liquid nitrogen cooled cold well.
502.6
mg (
2.83
mmol)
KPzNHtBu was added with THF while the suspension was thawing. After stirring at room
temperature for 1 hour,
207.0
mg (
0.94
mmol) iodosylbenzene was added with TH
F. After 4 hours,
the solvent was removed under reduced pressure. The brown solid was transferred to a co
a
rse
porosity glass frit with celite using
50 mL
pentane. The desired compound was extracted using
toluene until the filtrate appeared colorless. This
red
-
brown solution was dried completely under
reduced pressure; the resulting solid
(1.207 g obtained)
is used
in the following steps
assuming a
molecular formula of LFe
3
O(PzNHtBu)
3
, however this could not be con
firmed via X
-
ray
crystallography
due to its
poor crystallinity
.
110.7 mg (0.076 mmol) of the LFe
3
O(PzNHtBu)
3
solid was dissolved in 5 mL THF. 33.0
mg (0.076 mmol) Fe(OTf)
2
•
2 MeCN was added with 1 mL THF. After 45 minutes, 26 mg (0.464
mmol) KOH was added as a THF suspension. After 18 hours, the r
eaction appeared dark blue; this
S
9
solution was transferred to a Schlenk tube and dried under vacuum at 100
°
C for 1 hour. The
reaction mixture is suspended in MeCN and the blue precipitate was collected over a coarse
porosity frit with celite. The precipita
te was washed with MeCN until the filtrate was colorless,
and then dried under vacuum. The dry blue precipitate was extracted with toluene and dried under
reduced pressure. This residue was recrystallized via benzene/HMDSO vapor diffusion to yield
25.7 mg
(0.017 mmol; 22% yield) of
1
as a blue solid.
1
H NMR (300 MHz, C
6
D
6
):
δ 123.0 (br),
64.6 (br), 56.4, 50.1, 44.1, 41.0,
24.6, 19.6, 14.2, 12.2, 4.4, 3.2, 1.7,
-
40.6 (br) ppm
. UV
-
Vis (THF)
[ε (M
-
1
cm
-
1
)] 253 nm (5.19 x 10
4
), 494 nm (3.26 x 10
3
), 609 nm (3.81 x 10
3
).
Anal. calcd. (%) for
C
78
H
76
Fe
4
N
15
O
5
: C, 61.36; H, 5.02; N, 13
.76. Found:
C, 61.27; H, 5.40; N, 13.12.
The 18
-
O labeled cluster
could be prepared through the analogous protocol, substituting
K
18
OH for KOH.
The resulting product
has identical spectroscopic features to that of
1
, and was
used to prepare the
remaining
1
8
-
O labeled clusters (via oxidation
s
and
/or
deprotonation). ESI
-
MS analysis was consistent with
18
-
O incorporation
of
the cluster (Figure S
18
).
Synthesis
of
[LFe
3
O(PzNHtBu)
3
Fe(OH)][OTf]
(2)
.
265.2
mg
(
0.17
mmol)
LFe
3
O(PzNHtBu)
3
Fe(OH)
was dissolved in
5
mL
THF. This was transferred to a stirring
suspension of
52.3
mg (0.1
6
mmol) [Fc][OTf] in 3 mL THF. After 1 hour, the reaction was
concentrated under
vacuum to 1 mL
and 15 mL
toluene
was added. The reaction was stirred for
15 minutes and the resulting red
-
pur
ple precipitate was collected on a coarse frit with celite and
dried completely under vacuum. The red
-
purple solid was extracted by washing with MeCN until
the filtrate appeared colorless; this solution was dried under reduced pressure. The resulting
resid
ue was recrystallized via THF/Et
2
O vapor diffusion to yield 211
mg of red
-
purple crystals of
2
(0.13
mmol;
82
% yield)
.
1
H NMR (300 MHz, CD
3
CN):
δ
127.2 (br), 82.1 (br), 54.4, 49.0, 22.1,
16.5 (br), 14.1, 13.8, 13.3, 10.3 (br), 8.4, 7.8, 7.3, 1.0,
-
4.9,
-
5.
1,
-
22.8 (br)
ppm. UV
-
Vis (
ACN
)
S
10
[ε (M
-
1
cm
-
1
)] 2
43
nm (5.
96
x 10
4
),
328
nm (
8.83
x 10
3
), 503
nm (
4.88
x 10
3
).
Anal. calcd. (%) for
C
79
H
76
F
3
Fe
4
N
15
O
8
S: C, 56.61; H, 4.57; N, 12.54. Found: C, 56.72; H, 4.70; N, 12.03.
Synthesis
of
[LFe
3
O(PzNHtBu)
3
Fe(OH)][OTf]
2
(3)
.
102.3
mg
(
0.06
mmol)
[LFe
3
O(PzNHtBu)
3
Fe(OH)][OTf]
was dissolved in
3
mL
DCM
and a
solution
of
20.3
mg (
0.06
mmol) [Fc][OTf] in 2 mL
DCM was transferred to this stirring solution
. After 2 hours, 10 mL
pentane was added to the reaction and the blue pr
ecipitate was collected on a coarse porosity glass
frit with celite. The blue powder was dried under vacuum
and extracted with DCM until colorless,
and recrystallized from DCM/Et
2
O to obtain 76.8 mg of
3
as blue crystals (69% yield)
1
H NMR
(300 MHz, CD
2
Cl
2
):
δ 144.3 (br), 103.7 (br), 82.0, 79.7, 66.0, 63.1, 15.5, 12.8, 9.9, 3.5, 1.2,
-
0.5,
-
2.3 (br),
-
11.6 (br) ppm.
[ε (M
-
1
cm
-
1
)] 238 nm (5.76 x 10
4
), 345 nm (7.74 x 10
3
), 634 nm (4.80 x
10
3
).
Anal. calcd. (%) for C
80
H
76
F
6
Fe
4
N
15
O
11
S
2
: C, 52.65; H, 4.20; N,
1
1.51
. Found:
C, 51.70; H,
4.37; N, 11.11.
Synthesis
of
[LFe
3
O(PzNHtBu)
3
Fe(OH)][OTf]
3
(4)
.
42.9
mg
(0.024
mmol)
[LFe
3
O(PzNHtBu)
3
Fe(OH)][OTf]
2
was dissolved in 2 mL DCM and 8.1 mg (0.024 mmol)
[Fc][OTf] was added with 2 mL DCM. After 30 minutes, the reaction
was concentrated and 10
mL Et
2
O was added to produce a green precipitate. This was collected on a frit over celite and
rinsed with Et
2
O. The precipitate was collected with DCM and recrystallized via vapor diffusion
of Et
2
O to obtain 39.0 mg (0.020 mmol; 8
2% yield)
4
as green crystals.
1
H NMR (300 MHz,
CD
2
Cl
2
):
δ 95.2, 85.0, 14.5,
-
1.8,
-
44.9.
-
48.3 ppm.
UV
-
Vis (ACN) [ε (M
-
1
cm
-
1
)] 242 nm (7.11 x
10
4
), 355 nm (8.85 x 10
3
), 748 nm (7.39 x 10
3
).
Anal. calcd. (%) for C
8
1
H
76
F
9
Fe
4
N
15
O
1
4
S
3
: C,
49.28
; H,
3.88
; N,
10.64
. Found:
C, 49.19; H, 4.09; N, 10.02.
Synthesis
of
LFe
3
O(PzNHtBu)
3
Fe(O)
(5)
.
102.6
mg
(
0.
06
mmol)
[LFe
3
O(PzNHtBu)
3
Fe(OH)][OTf]
was dissolved in
15mL
THF and froze in a liquid nitrogen
S
11
cooled cold well.
7.2
mg (
0.
06
mmol) KOtBu was added to
the thawing
solution
, and the reaction
was stirred at room temperature for 1 hour. The solvent was removed under reduced pressure and
the crude product was recrystallized via benzene/HM
DSO vapor diffusion to obtain 2
6.2
mg of
5
as purple crystals (0.02
mmol;
2
8
% yiel
d).
1
H NMR (300 MHz, C
6
D
6
):
δ 105.9 (br),
58.5 (br),
55.3, 53.0, 40.9, 38.9, 33.9, 21.8, 14.4, 11.7, 2.4, 1.1,
-
21.5 (br)
ppm. UV
-
Vis (
THF
) [ε (M
-
1
cm
-
1
)] 24
8
nm (
4.40
x 10
4
),
342
nm (
6.73
x 10
3
), 5
39
nm (
3.41
x 10
3
).
Anal. calcd. (%) for
C
78
H
7
5
Fe
4
N
15
O
5
: C
, 61.
40
; H,
4.95
; N, 13.7
7
. Found:
C, 60.04; H, 5.01; N, 13.06 (Calcd. (%) for
C
78
H
75
Fe
4
N
15
O
5
•
0.5 (C
6
H
18
OSi
2
): C, 60.
0
5; H, 5.27; N, 13.08; compound recrystallized from
benzene/HMDSO).
Synthesis
of
[LFe
3
O(PzNHtBu)
3
Fe(O)][OTf]
(6)
.
50.3
mg
(0.03
mmol)
[LF
e
3
O(PzNHtBu)
3
Fe(OH)][OTf]
2
was dissolved in 2 mL THF/DCM (1:1) and froze in a liquid
nitrogen cooled cold well. 8 mg (0.03 mmol) Ph
3
PCH
2
was added to the thawing solution as a THF
solution. The reaction turned a deep blue, and at this point care was taken
to avoid warming the
mixture to room temperature. The compound was precipitated by addition of cold Et
2
O, and the
precipitate was dried under vacuum to yield
6
as a blue powder. NMR analysis of this powder
revealed the presence of residual [Ph
3
PCH
3
][OTf],
which were difficult to remove with Et
2
O
washes. This mixture could be recrystallized in THF/Et
2
O at
-
35
°
C to obtain X
-
ray quality crystals
of
6
; however, due to the decomposition of this compound, obtaining
6
cleanly
as a bulk solid for
elemental analysi
s was unsuccessful.
1
H NMR (300 MHz, CD
3
CN):
δ 122.2 (br), 90.2 (br), 68.5,
66.1, 55.0, 53.2, 14.5, 13.9, 13.0, 10.7,
-
31.0 (br) ppm.
Synthesis
of [LFe
3
O(PzNHtBu)
3
Fe(O)][OTf]
2
(7).
43.0
mg [LFe
3
O(PzNHtBu)
3
Fe(OH)][OTf]
2
(
3
; 0.0
2
mmol)
was dissolved in 1:1 D
CM/THF and froze in a liquid nitrogen cooled cold well.
A
THF solution of
6.8
mg Ph
3
PCH
2
(0.0
2
mmol)
was added to the thawing solution
.
The reaction
S
12
was then
combined, while thawing,
with
a DCM solution of
7.8
mg [Fc][OTf] (0.0
2
mmol).
Keeping this mixture
as cold as possible, thawing Et
2
O was added to precipitate the oxidized
cluster;
The blue
-
green solid was collected on a fine porosity glass frit, and dried under vacuum.
The
1
H NMR of this solid always contained minor amounts of impurities (<20%
, mostly
ascribed
to
3
and
4
), which
7
could not be isolated from due to its thermal instability.
For
any subsequent
reactions performed on this material, the moles of initial cluster
3
were used to approximate the
amount of
7
present.
1
H NMR (300 MHz, 1:1 CD
3
CN/CD
2
Cl
2
):
δ 145.6 (br), 105.4 (br), 85.2, 81.4,
71.0, 67.2, 19.0, 13.8, 11.1, 8.8,
-
61.1,
-
67.3 (br).
S
13
Figure S1.
1
H NMR spectrum (300 MHz) of 2
-
tert
-
butyl
-
isoxazolium tetrafluoroborate in
(CD
3
)
2
CO.
Figure S2.
1
H NMR spectrum (400 MHz) of
N
-
tert
-
butyl
-
1
H
-
pyrazol
-
3
-
amine
in CD
2
Cl
2
.
S
14
Figure S3.
13
C{
1
H} NMR spectrum (100 MHz) of
N
-
tert
-
butyl
-
1
H
-
pyrazol
-
3
-
amine
in CD
2
Cl
2
.
Figure S
4
.
1
H NMR spectrum (300 MHz) of
LFe
3
O(PzNHtBu)
3
Fe(OH)
(
1
)
in C
6
D
6
. The sharp
signal ~ 95 ppm is a spectral artifact.
S
15
Figure S
5
.
1
H NMR spectrum (300 MHz) of [
LFe
3
O(PzNHtBu)
3
Fe(OH)
][OTf]
(
2
)
in CD
3
CN
.
The sharp
signal ~ 90 ppm is a spectral artifact.
Figure S
6
.
1
H NMR spectrum (300 MHz) of [
LFe
3
O(PzNHtBu)
3
Fe(OH)
][OTf]
2
(
3
)
in CD
2
C
l
2
.
S
16
Figure S
7
.
1
H NMR spectrum (300 MHz) of [
LFe
3
O(PzNHtBu)
3
Fe(OH)
][OTf]
3
(
4
)
in CD
2
C
l
2
.
Figure S
8
.
1
H NMR spectrum (300 MHz) of
LFe
3
O(PzNHtBu)
3
Fe(O)
(
5
)
in C
6
D
6
.
S
17
Figure S
9
.
1
H NMR spectrum (
4
00 MHz) of
[
LFe
3
O(PzNHtBu)
3
Fe(O)
][OTf]
(
6
)
in
THF
/C
6
D
6
.
Figure S10.
1
H NMR spectrum (300 MHz) of [
LFe
3
O(PzNHtBu)
3
Fe(O)
][OTf]
2
(
7
) in
1:1
CD
3
CN
/CD
2
Cl
2
.