Stereoretentive Ligand Exchange Reactions of N-Fused Porphyrin Ruthenium(II) Complexes

Article abstract of DOI:10.1021/acs.inorgchem.7b01972

The ligand exchange reactions of the ruthenium(II) complex of N-fused tetraphenylporphyrin, Ru(NFp)(CO)₂Cl (2), with various anions were investigated. The chloride ligand of the isomers 2a-c was stereoretentively exchanged with bromide (Br^-), iodide (I^-), and acetate (AcO^-) anions in toluene at 100 °C, structures of which were confirmed by ¹H NMR as well as single crystal X-ray diffraction analysis. The silver (AgOAc, AgOTf) and boron (NaBPh₄) reagents also afforded the corresponding stereoretentive products. On the other hand, the reaction with NaBH₄ afforded the hydride complex Ru(NFp)(CO)₂H (7) with low stereospecificity, showing a higher reactivity of 2c than other isomers. The ligand dissociation mechanism was proposed with the help of theoretical calculations on the plausible five-coordinated intermediates.

Full text of DOI:10.1021/acs.inorgchem.7b01972

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Stereoretentive Ligand Exchange Reactions of N‑Fused Porphyrin
Ruthenium(II) Complexes
†
†
†
§
,†
Hideaki Matsuo, Motoki Toganoh, Masatoshi Ishida, Shigeki Mori, and Hiroyuki Furuta*
†Department of Chemistry and Biochemistry, Graduate School of Engineering, and the Center for Molecular Systems, Kyushu
University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan
§
Advanced Research Support Center, Ehime University, Matsuyama 790-8577, Japan
*
S Supporting Information
ABSTRACT: The ligand exchange reactions of the
ruthenium(II) complex of N-fused tetraphenylporphyrin,
Ru(NFp)(CO) Cl (2), with various anions were investigated.
2
The chloride ligand of the isomers 2a−c was stereoretentively
−
−
exchanged with bromide (Br ), iodide (I ), and acetate
−
(
AcO ) anions in toluene at 100 °C, structures of which
were confirmed by H NMR as well as single crystal X-ray
1
diffraction analysis. The silver (AgOAc, AgOTf) and boron (NaBPh ) reagents also afforded the corresponding stereoretentive
4
products. On the other hand, the reaction with NaBH afforded the hydride complex Ru(NFp)(CO) H (7) with low
4
2
stereospecificity, showing a higher reactivity of 2c than other isomers. The ligand dissociation mechanism was proposed with the
help of theoretical calculations on the plausible five-coordinated intermediates.
2
8−30
INTRODUCTION
group elements
were synthesized successfully. The
■
relevant ruthenium(II) complex of N-fused tetraphenylpor-
phyrin (Ru(NFp)(CO) Cl, 2) was also prepared by heating
NFpH with [RuCl (CO) ] in toluene (Scheme 1). The three
isomers (diastereomers) (2a−c) were separated by silica gel
column chromatography, and the structures were unambigu-
ously characterized by X-ray crystallographic analysis. Due to
the tight binding of NFp ligand with three nitrogen atoms, the
complexes 2a−c were rather stable, and the isomerization did
not proceed even at 100 °C in toluene.
In this paper, the ligand exchange reactions of Ru(NFp)-
CO) Cl (2) were studied in detail. The chloride ligand (Cl )
was replaced by various nucleophilic anions (Br , I , Ph ,
AcO , TfO ), affording the corresponding NFp-ruthenium
complexes, stereoretentively. In addition, Cl−H exchange
reaction was also investigated by using NaBH . Because of
the tight binding of Ru metal to the asymmetric NFp ligand,
the ruthenium complex 2 would provide a good reference for
the ligand exchange mechanism of half-sandwich complexes like
Half-sandwich ruthenium complexes have gathered a lot of
attention from the interest of their potential applications in
18
2
1
,2
3,4
2 3 2
various fields such as catalysts, molecular devices, medicinal
5
,6
chemistry,
etc. A variety of half-sandwich derivatives
including chiral ones have been synthesized by the ligand
exchange reactions on the metal of half-sandwich complexes.
For example, Noyori et al. reported the formation of chiral
ruthenium hydride complex form its chloride precursor in the
asymmetric hydrogenation reaction of ketons. For controlling
the stereochemistry of chiral complexes with suppressing the
isomerization or racemization at the metal center, under-
standing of the ligand exchange reactions is indispensable.
The mechanistic study on the chiral half-sandwich complex
2
,7
8
−
(
2
−
−
−
9
,10
−
−
1
2 3
with a cyclopentadienyl ligand [CpRuL L L ] revealed that the
energy barrier of racemization depends on the associated
4
1
1,12
ligands.
On the other hand, in the porphyrinoid chemistry, the
ruthenium ion is usually coordinated by the tetrapyrrole
macrocyclic ligand to form a square planar or pyramidal
structure because of the ionic size matching to the macrocyclic
[
CpRu(CO) Cl]. A facile separation of each isomer by column
chromatography would also make ruthenium NFp complex
handling easier for the study.
2
1
3
core. The sandwich or half-sandwich type of ruthenium (or
iron) complexes are so far limited to the core-modified
RESULTS AND DISCUSSION
14
15
■
porphyrins such as porphycene, dithiaethyneporphyrin, and
1
6
Ligand Exchange Reactions of 2 with Various Anions.
triphyrin. Recently, we have synthesized a new type of
1
7,18
The complexes 2a−c were synthesized according to the
sandwich and half-sandwich ruthenium complexes
using a
18
19,20
previous report. Among three isomers, 2c was obtained as a
major product (2a: 6%, 2b: 12%, 2c: 63%), and thus 2c was
mainly subjected to the ligand exchange reactions (Scheme 2).
unique porphyrinoid ligand, N-fused porphyrin (NFpH, 1),
and studied the ligand rearrangement on the NFp platform.
18
NFp serves as a planar, tridentate, monoanionic nitrogen
−
ligand, which is isoelectronic as a cyclopentadienyl anion (Cp )
−
or trispyrazolylborate (Tp ). Accordingly, a wide variety of
Received: August 2, 2017
17,18,21−27
NFp complexes with transition metals
as well as main
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.7b01972
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Article
18
Scheme 1. Synthesis of Isomers of Ru(NFp)(CO) Cl (2a−c)
2
Scheme 2. Stereoretentive Ligand Exchange Reactions of 2c
Figure 1. X-ray structures of 3c (a) and 3b (b). The thermal ellipsoids
are described at the 50% probability level.
stereochemistry of the product would be governed kinetically
rather than thermodynamically.
When tetrabutylammonium iodide (n-Bu NI) was used in
4
place of n-Bu NBr, the corresponding iodide complex Ru-
4
(
NFp)(CO) I (4c) was obtained in the same manner. The laser
2
desorption mass analysis gave the peaks of m/z = 840 and 713,
+
+
corresponding to [4c−2(CO)] and [4c−2(CO)−I] , respec-
1
tively. The H NMR spectrum of 4c showed almost identical
signals as 3c, as expected from the stereoretentive ligand
exchange reaction.
Next, phenyl anion (i.e., benzenide) was subjected to the
exchange reaction (Scheme 2, path b). By treating 2 (2a, 2b, or
At first, the chloride-bromide exchange reaction was
examined (Scheme 2, path a). When a mixture of 2c and
tetrabutylammonium bromide (n-Bu NBr) in 1,4-dioxane was
4
heated at 100 °C, a new red color spot was gradually observed
on a thin-layer chromatography (TLC) plate. Below 100 °C,
such change was not observed. The product was isolated by
silica gel column chromatography and identified as Ru(NFp)-
2c, respectively) with sodium tetraphenylborate (NaBPh ) at
4
100 °C, Ru(NFp)(CO) Ph (5) was obtained stereoretentively
2
(5a: 83%, 5b: 65%, 5c: 87%). In this ligand exchange reaction,
the sodium tetraphenylborate worked as a benzenide source
31,32
(
CO) Br (3c) by the several spectroscopic methods. For
similar to the palladium catalyzed cross-coupling reactions.
IR spectra showed a set of CO stretching bands at 2023 and
2
1
example, the H NMR spectrum of 3c shows a set of NFp
signals being very similar to the starting material 2c. Laser
ionization MS spectrum shows the peaks of m/z = 794 and 713,
corresponding to [3c−2(CO)] and [3c−2(CO)−Br] ,
respectively. The presence of two CO groups was confirmed
by the observation of IR stretching bands at 2044 and 1985
cm and the C NMR signals at δ = 192.1 and 192.5 ppm.
Configuration of the ligands in 3c was determined by the
preliminary single crystal X-ray diffraction analysis (Figure 1a).
The newly introduced bromide ligand in 3c was in the same
position as chloride in 2c. Thus, the chloride-bromide ligand
exchange reaction of 2c underwent in a stereoretentive manner.
−
1
−1
1956 cm (5a), 2021 and 1955 cm (5b), 2010 and 1942
−1
−1
cm (5c), respectively. These values are lower by 23−30 cm
+
+
−1
than the corresponding chloride complex 2 (2046−1972 cm ),
which suggests a strong coordination of the benzenide ligand to
1
the Ru center. In the H NMR spectra of 5b (and 5c), the three
−1
13
signals of the introduced phenyl group were observed in an
upper-field region at δ = 5.22 (6.15) (2H, o-phenyl), 6.49
(6.77) (2H, m-phenyl), and 6.66 (6.83) ppm (1H, p-phenyl)
due to the shielding effect of the NFp ligand. While the phenyl
signals of 5b and 5c were observed as the sharp signals at room
temperature, the corresponding signals of 5a were significantly
broadened under the same conditions, suggesting slow rotation
of the phenyl group of 5a. They became sharp at −50 °C
possibly due to the stopped spinning on the NMR time scale,
and the phenyl signals were observed in an unsymmetrical
manner: δ = 2.86 and 6.28 (o-phenyl), 5.18 and 6.63 (m-
phenyl), and 6.10 ppm (p-ph). The slow rotation of the phenyl
group of 5a compared to 5b and 5c would be explained
Similarly, the reaction of 2b with n-Bu NBr at 100 °C also gave
4
the stereoretentive product 3b, whose structure was unambig-
uously identified by single crystal X-ray analysis (Figure 1b). In
the density functional theory (DFT) calculations at the
B3LYP/6-31SDD level, 3c is thermodynamically more stable
than 3b by 0.29 kcal/mol (see Supporting Information).
Nevertheless, 3c was not obtained in this reaction. Thus,
B
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Figure 2. Optimized structures of 5a−c.
reasonably by the steric circumstances. The optimized
structures of 5a−c at the B3LYP/6-31SDD level are shown
in Figure 2. While the phenyl group of 5b or 5c placed above
the pyrrole ring, 5a placed above the rigid tripentacyclic moiety
(
yellow-colored), which would cause steric hindrance. Practi-
cally, the o-phenyl signals of 5a were more influenced by the
shield effect of NFp ring current (av 4.48 ppm) of 5b (5.22
ppm) and 5c (6.15 ppm).
Successively, the ligand exchange reaction of 2c with acetate
−
anion (AcO ) was investigated using an excess amount of
potassium acetate. In this reaction, a higher temperature was
necessary to promote the ligand exchange, and at 150 °C, the
complex 6c was formed along with 6a and 6b (76% yield in
total, 6a:6b:6c = 1.05:0.72:1.00 determined from the NMR
signals). At this temperature, isomerization of 2c to 2a and 2b
occurred. As the result, the reaction afforded a mixture of
isomers 6a−c. To avoid the isomerization at high temperature,
halogen abstraction reaction of 2c with silver acetate (AgOAc)
was attempted at 100 °C. Then, the reaction proceeded
smoothly to afford a stereoretentive product Ru(NFp)-
Figure 3. X-ray structures of (a) 6a and (b) 6c. The thermal ellipsoids
are described at the 50% probability level.
1
8
Hydride Complex Formation. Metal-hydride complexes,
drawn as MH L , are important because of their significant
n
m
reactivity as the catalyst for hydride insertion, metathesis,
8,33,34
reductions, etc.
Thus, hydride exchange reaction of Ru-
NFP complex was attempted using various hydride sources.
When a THF solution of 2 (isomeric mixture) was heated at 60
(
CO) (OAc) (6c) in a high yield (96%). The complex 6c
2
was alternatively synthesized from 2c in a stepwise manner, that
is, treatments first with silver triflate (AgOTf) and then
potassium acetate (Scheme 3). The first step proceeded at
°
C with sodium borohydride (NaBH ), formation of hydride
complexes was suggested from the H NMR spectrum of the
4
1
reaction mixture, where the highly upfield-shifted Ru−H signals
35
were observed around δ = −13 ppm. After separation by silica
Scheme 3. Two Synthetic Pathways of 6c
gel column chromatography with CH Cl , Ru(NFp)(CO) H
2
2
2
3
6−38
(
7c), and N-confused porphyrin (NCP)
were obtained as
major products in 21% and 47% yields, respectively (Scheme
). Electrospray ionization mass spectrometry (ESI-MS) of 7c
4
shows the peak of m/z = 771.13821, corresponding to the
r u t h e n i u m h y d r i d e c o m p l e x ( c a l c u l a t e d
12
C461H29 N416O2 Ru ([M + H ]) = 771.13340). The H
14
102
+
1
1
NMR analysis of the recovered 2 (initial isomeric mixture ratio,
2
a:2b:2c = 1.0:3.5:4.3) showed the ratio 2a:2b:2c =
1
.0:1.7:0.13. The result indicates 2c was more reactive than
the other isomers toward NaBH . On the other hand, when the
4
isolated 2c was used as the starting material to check the
stereospecificity, formation of isomers 7a and 7b along with the
major product 7c (7a: 7b: 7c = 0.5:0.06:1.0) was confirmed by
1
the H NMR signals in the upfield hydride region. These results
indicate that the Cl−H exchange reaction did not proceed
stereospecifically. When sodium triacetoxyborohydride (NaBH-
(OAc) ), a weaker hydride than NaBH , was used as a hydride
room temperature to afford an intermediate complex Ru-
3
4
(
NFp)(CO) (OTf). Formation of triflate compound was
source, the reaction did not occur even with an excess amount
of reagent. In contrast, the reaction with NaH, a stronger
hydride, resulted in the formation of NCP only. The different
selectivity and reactivity of hydrides from that of other
nucleophilic anions investigated above may suggest the
intervening of different reaction pathways in the Cl−H
exchange reactions, which remains to be solved.
2
detected by the laser desorption mass analysis as m/z = 862
+
[2c-2(CO)] . The second triflate-acetate ligand exchange step
also proceeded below 100 °C due to the better leaving group
nature of the triflate anion. The structures of 6a and 6c were
unambiguously determined by single crystal X-ray analysis
(Figure 3).
C
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Scheme 4. Hydride Complex Formation from the Ligand Exchange Reaction of 2 with NaBH4
Figure 4. Ligand dissociation mechanism of 3c formation and its isomerization.
Figure 5. Energy profile for the rotation pathways of the dissociated intermediates 2′.
4
0
7
c was also obtained selectively by the reaction with lithium
Meerwein−Ponndorf−Verley reduction reagent. Likewise,
lithium ion may accept the lone pair of the chloride ligand
and hydride-ruthenium interaction to make a six-membered
ring intermediate (Figure S10). The least crowded 2c could
easily form the intermediate.
diisopropylamide (LDA) even when the mixture of three
isomers of 2 was used. Isomeric pure 7c was selectively
obtained from the mixture of the three isomers 2a−c. In the
case of half-sandwich-type ruthenium-hydride complexes,
RuCp(CO) H was formed from RuCp(CO) Cl with iso-
Regarding the stability of the hydride complex, 7c in the solid
state was stable at room temperature, and no change was
2
2
39
propanol and bases. LDA was known to serve as the
D
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1
observed by H NMR even after one month. However, in the
λmax (nm) of “c” type isomers are shifted to a shorter-
wavelength region: 2c (939.0) vs 2a (963.0) and 2b (950.0); 5c
(925.0) vs 5a (953.0) and 5b (940.0); 6c (934) vs 6a (954)
and 6b (949). Among 2−6, significantly large blue-shifts are
observed with the electron-donating phenyl-substituted 5 and
acetate compound 6. In contrast, bromide 3 and iodide 4
complexes show small differences from that of chloride
compound 2. These data are consistent with the previous
observation that the NFp ligand gets perturbations strongly
halogenated solvent like CH Cl , 7c was gradually changed to a
2
2
1
ruthenium-halogen complex. Accordingly, the H NMR
spectrum of 7c in CDCl3 gradually changed and almost
converted into that of 2c after 91 h at room temperature.
Reaction Mechanism. The stereoretentive ligand exchange
reaction of Ru(NFp)(CO) Cl with halide “X ” might be
explained by the ligand dissociation mechanism (Figure 4).
Namely, the chloride ligand is first released from 2 as Cl , then
an excess amount of nucleophilic halide attacks the
coordinatively unsaturated Ru of the intermediate, [Ru(NFp)-
−
2
−
18
from the trans-located ligands to the fused ring of NFp.
The theoretical HOMO−LUMO energies of 2−6 and
frontier orbitals of 5a−c as representatives are summarized in
Table 2 and Figure 7, respectively. All of the LUMOs mainly
+
(
CO) ] (2′). This intermediate could hold a pseudotetrahe-
2
dral structure while maintaining the stereochemistry of the
starting complex because of the high-energy barrier of the
isomerization at 100 °C. A similar mechanism was suggested in
the ligand exchange reactions of chiral half-sandwich ruthenium
Table 2. Calculated Energies (EHOMO, ELUMO, ΔE ) of 2−6
L−H
and Experimental HOMO−LUMO Gaps Estimated from
7
,10,41−44
cyclopentadienyl complexes,
intermediates were not detected in the spectral analyses.
although unsaturated
λ
Values (in eV)
max
45
To gain the insight into the dissociated intermediate (2′), the
activation energies of the ligand rotation of each step were
calculated by the DFT methods (Figure 5). The energy profile
compd
EHOMO
ELUMO
ΔEL−H
ΔEλmax
2a
2b
2c
3a
3b
3c
4a
4b
4c
5a
−4.95
−5.02
−5.06
−4.95
−5.02
−5.06
−4.99
−5.06
−5.10
−4.89
−4.91
−4.95
−4.97
−5.01
−5.02
−2.95
−2.96
−2.97
−2.96
−2.97
−2.98
−3.01
−3.02
−3.03
−2.85
−2.85
−2.83
−2.93
−2.93
−2.93
2.00
2.06
2.09
1.99
2.05
2.09
1.98
2.03
2.07
2.04
2.07
2.11
2.04
2.08
2.09
1.29
1.31
1.32
−
1.30
1.32
−
shows the stereoretentive pseudotetrahedral-type intermediates
‡
(
2
2a′−2c′) were preferred to the planar intermediates (2a′ −
‡
c′ ). The estimated rotation energy barriers are within a range
of 25−30 kcal/mol. These values are not sufficiently high to
46
suppress the thermal isomerization at 100 °C. However, if the
formation of 16e unsaturated intermediate 2′ was the rate-
determining step, then it is likely the cationic intermediate 2′
immediately reacts with a surrounding nucleophile present in
an excess amount before ligand rotation. Of course, other
mechanisms involving the seven-coordinated ruthenium
complex intermediate or σ-bond metathesis cannot be ruled
−
1.32
1.30
1.31
1.33
1.30
1.32
1.34
5b
5c
6a
6b
6c
47−49
out at this moment.
Absorption Properties of Complexes 2−6. The
absorption spectra of a series of ruthenium-NFp complexes
2c−6c are shown in Figure 6, and the data are summarized in
show the π-orbitals of NFp ligand with small contribution of
metal d-orbitals or the other ligands. Meanwhile, HOMOs
show the contribution of the introduced ligands as well as the
NFp ligand and metal orbitals (Figures S11−S15). Among 5a−
c, for example, the contributions of benzenide ligand in HOMO
and HOMO−1 was seen in order of 5a > 5b > 5c. Accordingly,
5a has the highest HOMO energy (−4.89 eV), while 5b is
moderate (−4.91 eV) and 5c is the lowest (−4.95 eV). On the
other hand, the LUMO energies are almost same. Thus, the
HOMO−LUMO gaps (ΔEL−H) were in order of a < b < c,
which is consistent with the absorption properties.
CONCLUSION
In this study, the ligand exchange reactions of Ru(NFp)-
■
(
Figure 6. UV−vis-NIR absorption spectra of 2c−6c in CH Cl .
2
2
CO) Cl (2) with various anions were investigated. The
2
chloride ligand of 2 was exchanged at 100 °C in the presence of
−
−
−
50,51
bromide (Br ), iodide (I ), and acetate (AcO ) anions in
Table 1. Basically, the spectra resemble that of NFp ligand.
Comparing the longest wavelength of the Q-like band of each
complex, corresponding to the HOMO−LUMO transition, the
toluene solution. By using the stereoisomers 2a−c, stereo-
1
retentive exchange reaction was demonstrated by the H NMR
and single crystal X-ray structural analysis. The silver (AgOAc,
AgOTf) and boron (NaBPh ) reagents also afford stereo-
4
Table 1. Longest Wavelength of the Absorption Maximum
retentive products. However, the reaction with NaBH afforded
4
(
λmax, nm) of 2−6 in CH Cl
2
2
the hydride complex Ru(NFp)(CO) H (7) with low stereo-
2
specificity, showing a higher reactivity of 2c than other isomers.
The ligand dissociation mechanism was proposed with the help
of theoretical calculations on the plausible five-coordinated
intermediates. The facile synthesis of stereocontrolled NFp-
Ru(II) complexes by the simple ligand exchange reactions
isomer
Cl (2)
Br (3)
I (4)
Ph (5)
OAc (6)
a
b
c
963.0
950.0
939.0
−
952.5
−
−
938.5
953.0
940.0
925.0
954.0
949.0
934.5
938.0
E
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Figure 7. Kohn−Sham orbitals of 5a−c; LUMO (top), HOMO (middle), and HOMO−1 (bottom).
would be attractive for use as asymmetric catalysts. Further
study toward such direction is currently underway.
found. Vibrational modes corresponding to imaginary frequency were
consistent with the rotational mechanism discussed below.
Ru(NFp)(CO) Br (3). Ru(NFp)(CO) Cl (2b or 2c, 6 mg, 7.5
2
2
1
8
μmol) in 1,4-dioxane (3 mL) was added in a Schlenk tube under
EXPERIMENTAL SECTION
■
argon. Then tetrabutylammonium bromide (n-Bu NBr: 29 mg, 12
4
General. Commercially available solvents and reagents were used
without further purification unless otherwise mentioned. Thin-layer
chromatography (TLC) was carried out on aluminum sheets coated
with silica gel 60 F254 (Merck). Preparative separation was performed
by silica gel flash column chromatography (KANTO silica gel 60N,
spherical, neutral, 40−50 μm), silica gel gravity column chromatog-
raphy (KANTO silica gel 60N, spherical, neutral, 63-210 μm), and
equiv) was added, and the solution was heated at 100 °C for 144 h.
After cooling, the solvent was removed under vacuum. The residue
was dissolved in dichloromethane (CH Cl ) and subjected to the silica
2
2
gel column chromatography with CH Cl as eluent for separation. The
2
2
first red fraction afforded Ru(NFp)(CO) Br (3b, 3.0 mg, 47%; 3c, 2.9
2
mg, 45%). Unreacted starting material (2b or 2c) was recovered from
the second fraction.
alumina column chromatography (γ-Alumina KCG-1525W, Sumito-
1
3
b: H NMR (CDCl , 500 MHz, ppm): δ 7.21 (d, J = 4.5 Hz, 1H,
3
1
mo). H NMR spectra were recorded in CDCl solution on a JNM-
3
β-pyrrole), 7.34 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.54 (d, J = 4.5 Hz, 1H,
β-pyrrole), 7.54−7.56 (m, 1H), 7.60−7.65 (m, 3H), 7.69 (d, J = 5.5
Hz, 1H, β-pyrrole), 7.71−7.82 (m, 10H), 7.96−7.97 (br, 2H), 8.26−
ECX (500 MHz) FT-NMR spectrometer, and chemical shifts were
reported relative to a residual proton of a deuterated solvent, CHCl
3
1
3
(
δ = 7.26) in ppm. C NMR spectra were recorded in CDCl solution
3
8
.27 (m, 2H), 8.66 (d, J = 7.5 Hz, 2H), 8.68 (d, J = 5.0 Hz, 1H, β-
on the same instrument at 125 MHz, and chemical shifts were
reported relative to CDCl3 (δ = 77.00) in ppm. UV−vis-NIR
absorption spectra were recorded on a Shimadzu UV-3150PC
spectrometer at ambient temperature. Mass spectra were recorded
on a Bruker Daltonics Autoflex-KK MALDI-TOF MS spectrometer.
High-resolution mass spectra were recorded on a JEOL JMS-T100CS
spectrometer (ESI-TOF mode). Cyclic voltammetry measurements
were performed on a CH Instrument Model 620B (ALS) equipped
with a Pt electrode. IR absorptions were recorded on FT/IR-4200
13
pyrrole), 9.19 (d, J = 6.0 Hz, 1H, β-pyrrole), 9.31 (s, 1H, 21-H);
C
NMR (CDCl , 125 MHz, ppm): δ 113.5, 114.9, 118.6, 121.9, 125.5,
3
1
1
1
1
27.1, 127.7, 127.8, 127.9, 128.2, 128.6, 128.7, 128.8, 129.1, 129.6,
30.0, 131.2, 131.7, 132.6, 132.8, 134.8, 136.4, 137.5, 137.9, 138.4,
41.9, 143.3, 144.8, 147.9, 152.2, 152.5, 153.7, 158.3, 163.2, 192.3,
−1
92.9; IR (powder, cm ): 2043 (CO), 1983 (CO); UV−vis-NIR
(CH Cl , λ /nm, log ε): 352.0 (4.57), 523.0 (4.70), 860.5 (3.43),
2 2 max
+
9
52.5 (3.42); HRMS (ESI ): Found: m/z 851.04491, calcd for
12
C461H28 Br1 N4 O2 Ru (MH ): m/z 851.04187; Anal. calcd for
81
14
16
102
+
1
(
JASCO).
3
b·0.1CH Cl : C, 64.59; H, 3.20; N, 6.54. Found: C, 64.79; H, 3.20;
2 2
X-ray Crystallography. Single-crystal X-ray structural analyses
N, 6.57.
were performed on a Saturn equipped with a CCD detector (Rigaku)
using MoKα (multilayer mirror, monochromated, λ = 0.71069 Å)
radiation. The data were corrected for Lorentz, polarization, and
absorption effects. The structures were solved by the direct method of
1
3
c: H NMR (CDCl , 500 MHz, ppm): δ 7.36 (d, J = 4.5 Hz, 1H,
3
β-pyrrole), 7.44 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.54−7.61 (m, 5H),
7
.73−7.79 (m, 6H), 7.83−7.85 (m, 4H), 7.97 (br, 1H), 8.06−8.08 (m,
52
53
2H), 8.17−8.18 (m, 2H), 8.68 (d, J = 8.0 Hz, 2H), 8.86 (d, J = 4.5 Hz,
SHELXT 2014/5 and refined using the SHELXL-2016/6 program.
1
H, β-pyrrole), 9.28 (d, J = 4.5 Hz, 1H, β-pyrrole), 9.34 (s, 1H, 21-H);
All of the positional parameters and thermal parameters of non-
1
3
2
C NMR (CDCl , 125 MHz, ppm): δ 112.2, 112.4, 119.5, 121.6,
hydrogen atoms were refined anisotropically on F by the full matrix
3
1
1
1
25.3, 127.0, 127.6, 127.8, 128.2, 128.6, 128.6, 128.7, 128.8, 129.5,
29.8, 130.1, 130.4, 130.5, 132.2, 133.0, 133.6, 134.9, 136.5, 137.4,
least-squares method. Hydrogen atoms were placed at the calculated
positions and refined riding on their corresponding carbon atoms.
Calculation Details. All DFT calculations were achieved with a
38.2, 139.6, 139.9, 142.4, 144.7, 148.6, 152.5, 152.6, 153.3, 157.3,
54
−1
Gaussian 09 program package. The basis sets implemented in the
program were used. The B3LYP density functional method was used
with a 631SDD basis set for structural optimizations and frequency
calculation. The 631SDD bases set is composed of 6-31G(d,p) for
carbon, hydrogen, nitrogen, oxygen, chloride, and bromide and SDD
for iodide and ruthenium. Initial structures for ground state were based
on the X-ray structures, and those for transition state were arbitrarily
constructed. Ground-state geometries were fully optimized and
verified by the frequency calculations, where no imaginary frequency
was found. Transition-state geometries were also verified by the
frequency calculations, where only one imaginary frequency was
163.7, 192.1, 192.5; IR (powder, cm ): 2044 (CO), 1985 (CO);
UV−vis-NIR (CH
Cl , λmax/nm, log ε): 351.0 (4.60), 420.5 (4.34),
2
2
+
514.5 (4.74), 844.0 (3.41), 938.0 (3.39); HRMS (ESI ): Found: m/z
1
2
1
81
14
16
102
+
851.04532, calcd for
851.04187; Anal. calcd for 3c·0.3CH
C
H
28 Br
N
O
Ru
Cl : C, 63.61; H, 3.18; N, 6.41.
2
(MH ): m/z
46
1
4
2
1
2
Found: C, 63.47; H, 3.22; N, 6.47.
Ru(NFp)(CO)
I (4c). 2c (10 mg, 12 μmol), tetrabutylammonium
2
iodide (n-Bu NI, 45 mg, 10 equiv), and toluene (2 mL) were added in
4
a Schlenk tube under argon. Then the mixture was heated at 100 °C
for 47 h. After cooling, the solvent was removed under vacuum. The
residue was dissolved in CH Cl and subjected to the silica gel column
2
2
F
DOI: 10.1021/acs.inorgchem.7b01972
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
chromatography with CH Cl as eluent for separation. The first red
= 4.5 Hz, 1H, β-pyrrole), 7.41 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.43−
7.49 (m, 4H), 7.54−7.65 (m, 2H), 7.77−7.80 (m, 5H), 7.84−7.90 (m,
3H), 8.09−8.21 (m, 2H), 8.34 (d, J = 5.5 Hz, 2H, ph), 8.76 (d, J = 8.0
Hz, 2H, o-ph), 8.82 (d, J = 5.5 Hz, 1H, β-pyrrole), 9.24 (d, J = 4.5 Hz,
2
2
fraction afforded Ru(NFp)(CO) I (4c, 2.9 mg, 26%). Unreacted 2c
2
was recovered from the second fraction.
1
4
c: H NMR (CDCl , 500 MHz, ppm): δ 7.35 (d, J = 4.5 Hz, 1H,
3
β-pyrrole), 7.42 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.53 (d, J = 4.5 Hz, 1H,
β-pyrrole), 7.57 (t, J = 6.8 Hz, 1H, p-H), 7.60−7.63 (m, 3H), 7.74−
1H, β-pyrrole), 9.38 (s, 1H, 21-H); 13C NMR (CDCl , 125 MHz,
3
ppm): δ 111.9, 113.1, 119.6, 120.9, 122.5, 124.1, 126.2, 126.5, 127.2,
127.7, 127.9, 128.1, 128.4, 128.4, 128.7, 129.4, 129.5, 129.6, 130.0,
130.90, 131.8, 131.8, 132.7, 132.8, 135.4, 136.5, 138.1, 138.4, 138.4,
138.6, 140.3, 143.3, 145.8, 150.3, 151.8, 152.4, 154.7, 155.9, 157.4,
7
2
.79 (m, 5H), 7.83−7.86 (m, 4H, β-pyrrole and phenyl), 7.99 (br,
H), 8.07 (d, J = 7.6 Hz, 2H), 8.19−8.20 (m, 2H), 8.69 (d, J = 7.6 Hz,
m-ph), 8.86 (d, J = 4.5 Hz, 1H, β-pyrrole), 9.30 (d, J = 4.5 Hz, 1H, β-
pyrrole), 9.33 (s, 1H, 21-H); 13C NMR (CDCl , 125 MHz, ppm): δ
163.0, 196.5, 197.5; IR (powder, cm ); 2010 (CO), 1942 (CO);
−1
3
1
1
1
1
1
4
12.1, 112.4, 119.7, 121.3, 125.1, 126.9, 127.4, 127.7, 128.3, 128.4,
28.5, 128.7, 129.3, 129.6, 129.8, 129.9, 130.3, 132.1, 132.9, 133.6,
34.8, 136.6, 137.3, 137.8, 140.0, 142.5, 144.5, 148.4, 153.2, 153.3,
UV−vis-NIR (CH Cl , λ /nm, log ε): 352.5 (4.55), 523.0 (4.71),
2
2
max
+
647.0 (3.62), 834 (3.34), 925.0 (3.32); HRMS (ESI ): Found: m/z
847.16124, calcd for 12C521H33 N4 O2 Ru (MH ): m/z 847.16470;
14
16
102
+
1
−1
53.4, 156.5, 163.6, 192.2, 193.1; IR (powder, cm ): 2038 (CO),
Anal. calcd for 5c·0.4CH Cl : C, 71.53; H, 3.76; N, 6.37. Found: C,
2
2
981 (CO); UV−vis-NIR (CH Cl , λ /nm, log ε): 355.0 (4.66),
71.40; H, 3.97; N, 6.07.
2
2
max
+
31.5 (4.24), 516.0 (4.77), 849.0 (3.42), 938.5 (3.39); HRMS (ESI ):
Ru(NFP)(CO) (OAc) (6). To a mixture of three isomers of 2 (10.0
2
Found: m/z 897.03485, calcd for C461H28 I1 N4 O2 Ru1
1
2
127 14
16
102
mg, 12 μmol) in o-dichlorobenzene (3 mL), potassium acetate (61.0
mg, 50 equiv) was added, and the resulting solution was heated at 150
°C under Ar for 31 h. After cooling, the solvent was removed under
reduced pressure, and the residue was subjected to the silica gel
column chromatography with 1% methanol/CH Cl as eluent. The
+
(
6
MH ): m/z 897.03004; Anal. calcd for 4c·0.4CH Cl ·0.1C H : C,
2
2
6
14
0.16; H, 3.14; N, 5.97. Found: C, 60.07; H, 3.42; N, 5.83.
Ru(NFp)(CO) Ph (5). Sodium tetraphenylborate (5 equiv) was
2
added to Ru(NFp)(CO) Cl (2a, 10.3 mg, 2b, 15 mg or 2c, 8.6 mg) in
2
2
2
chlorobenzene (2 mL) in a Schlenk tube under nitrogen at room
temperature. Then the mixture was heated at 100 °C for 19 h. After
cooling, the solvent was evaporated, and the residue was separated by
silica gel column chromatography with CH Cl as eluent. The first red
fifth red fraction was evaporated to dryness and dried under vacuum to
give a mixture of 6a, 6b, and 6c (8.9 mg in total, 86%). 6.5 mg of 6 was
dissolved in 1% methanol/CH Cl and repeatedly separated by HPLC
2
2
with silica gel column (20 × 200 mm) using 1% methanol/CH Cl
2
2
2
2
fraction afforded Ru(NFp)(CO) Ph (5: 5a, 9.0 mg, 83%, 5b, 10.3 mg,
(flow rate was 7.0 mL/min and monitored at 500 nm). The product
mixture was separated into three fractions 6a (2.4 mg), 6b (1.2 mg),
2
65%, 5c, 7.9 mg, 87% yield), and the unreacted starting material (2a,
2
b, 2c) was recovered from the second red fraction.
and 6c (2.0 mg).
6a: H NMR (CDCl , 500 MHz, ppm): δ 0.52 (s, 3H), 7.12 (d, J =
1
1
5
a: H NMR (CDCl , −50 °C, 500 MHz, ppm): δ 2.86 (d, J = 8.0
3
3
Hz, 1H, o-ph), 5.18 (t, J = 6.8 Hz, 1H, m-ph), 6.10 (t, J = 7.0 Hz, 1H,
p-ph), 6.28 (d, J = 8.0 Hz, 1H, o-ph), 6.63 (t, J = 7.5 Hz, 1H, m-ph),
4.5 Hz, 1H, β-pyrrole), 7.33 (d, J = 4.0 Hz, 1H, β-pyrrole), 7.38 (d, J =
4.5 Hz, 1H, β-pyrrole), 7.55 (t, 1H, J = 7.5), 7.60−7.65 (m, 3H),
7.69−7.75 (m, 4H), 7.76−7.79 (m, 2H), 7.81−7.84 (m, 4H), 7.88 (d, J
= 4.5 Hz, 1H, β-pyrrole), 8.01 (s, 2H), 8.16−8.20 (m, 2H), 8.71 (d, J =
8.0 Hz, 2H, ph), 8.78 (d, J = 4.5 Hz, 1H, β-pyrrole), 9.21 (d, J = 4.5
7
7
7
7
.18 (d, J = 5.0 Hz, 1H, β-pyrrole), 7.41 (d, J = 3.5, 1H, β-pyrrole),
.41 (d, β-pyrrole, 2H, ph), 7.52 (d, J = 3.0 Hz, 1H, β-pyrrole), 7.51−
.35 (m, 1H), 7.57 (t, J = 8.3 Hz, 2H, ph), 7.65−7.69 (m, 3H, ph),
.74 (t, J = 7.5 Hz, 2H, ph), 7.81 (t, J = 7.8 Hz, 2H, ph), 7.85−7.87
Hz, 1H, β-pyrrole), 9.38 (s, 1H, 21-H); 13C NMR (CDCl , 125 MHz,
3
(
m, 3H, ph), 7.86 (d, J = 4.5 Hz, 1H, β-pyrrole), 8.14 (d, J = 5.0 Hz,
H, β-pyrrole), 8.23 (br, 2H, ph), 8.34 (d, J = 7.5 Hz, 1H, ph), 8.77 (d,
ppm): δ 21.4, 112.4, 112.8, 120.3, 120.8, 123.7, 126.2, 127.7, 128.3,
128.6, 128.7, 128.8, 129.3, 129.6, 129.7, 129.9, 130.0, 132.5, 133.1,
133.2, 134.2, 135.1, 136.4, 137.3, 137.7, 138.3, 140.3, 144.0, 145.4,
149.5, 153.2, 153.6, 154.3, 157.5, 160.6, 175.0, 193.2, 193.9; IR
1
J = 7.5 Hz, 2H, ph), 8.95 (d, J = 6.0 Hz, 1H, β-pyrrole), 9.47 (s, 1H,
2
1
1
1
1
1
1-H); 13C NMR (CDCl , −50 °C, 125 MHz, ppm): δ 111.0, 112.9,
3
−1
19.8, 120.2, 121.2, 124.0, 124.9, 126.0, 126.7, 127.1, 127.2, 127.6,
28.0, 128.2, 128.4, 128.6, 129.3, 129.4, 129.9, 130.3, 130.5, 133.1,
33.2, 133.7, 135.1, 136.7, 137.2, 137.4, 137.9, 138.6, 139.6, 141.8,
42.5, 145.8, 150.0, 151.7, 152.4, 152.9, 154.9, 158.6, 161.6, 195.9,
(powder, cm ): 2043 (CO), 1980 (CO); UV−vis-NIR (CH Cl ,
2
2
λ
/nm, log ε): 354.0 (4.63), 522.0 (4.72), 652.0 (3.73), 861.0 (3.49),
max
+
954.0 (3.50); HRMS (ESI ): Found: m/z 829.14150, calcd for
12
C481H31 N4 O4 Ru (MH ): m/z 829.13888; Anal. calcd for 6a·
14
16
102
+
1
−1
97.2; IR (powder, cm ): 2023 (CO), 1956 (CO); UV−vis-NIR
0.3H O: C, 68.79; H, 3.68; N, 6.69. Found: C, 68.54; H, 3.71; N, 6.66.
2
1
(
CH Cl , λ /nm, log ε): 354.5 (4.49), 448.5 (4.18), 525.0 (4.57),
6b: H NMR (CDCl , 500 MHz, ppm): δ 1.37 (s, 3H), 7.11 (d, J =
2
2
max
3
+
8
62.0 (3.32), 953.0 (3.32); HRMS (ESI ): Found: m/z 847.16232,
6.0 Hz, 1H, β-pyrrole), 7.36 (t, J = 3.8 Hz, 1H, β-pyrrole), 7.51 (d, J =
4.5 Hz, 1H, β-pyrrole), 7.54 (t, J = 7.0 Hz, 1H), 7.59−7.63 (m, 4H),
7.70−7.76 (m, 5H), 7.78−7.85 (m, 5H), 7.96 (br, 2H), 8.20−8.21 (m,
2H), 8.65 (d, J = 8.0 Hz, 2H), 8.66 (d, J = 4.5 Hz, 1H, β-pyrrole), 9.16
calcd for C521H33 N4 O2 Ru (MH ): m/z 847.16470; Anal. calcd
12
14
16
102
+
1
for 5a·0.2CH Cl ·2.2C H : C, 74.63; H, 6.05; N, 5.32. Found: C,
2
2
6
14
74.88; H, 5.87; N, 5.02.
1
13
5
b: H NMR (CDCl , 500 MHz, ppm): δ 5.22 (d, J = 7.0 Hz, 2H,
(d, J = 4.5 Hz, 1H, β-pyrrole), 9.27 (s, 1H, 21-H); C NMR (CDCl3,
3
o-ph), 6.49 (t, J = 7.5 Hz, 2H, m-ph), 6.66 (t, J = 7.5 Hz, 1H, p-ph),
125 MHz, ppm): δ 29.8, 113.2, 114.2, 118.7, 121.9, 125.2, 126.9,
127.8, 127.9, 128.1, 128.4, 128.5, 128.6, 128.7, 129.2, 129.3, 129.5,
129.6, 129.9, 131.1, 131.6, 132.4, 132.7, 134.9, 136.5, 137.9, 138.1,
138.6, 140.5, 143.5, 144.9, 146.4, 152.3, 152.4, 152.8, 158.9, 164.3,
7
7
.23 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.38 (d, J = 4.5 Hz, 1H, β-pyrrole),
.43 (d, J = 4.0 Hz, 1H, β-pyrrole), 7.49 (d, J = 6.5 Hz, 2H, ph), 7.53
(
t, J = 7.5 Hz, 1H, ph), 7.60−7.67 (m, 6H), 7.73−7.76 (m, 5H), 7.90
−
1
(
d, J = 4.0 Hz, 1H, β-pyrrole), 7.93 (br, 2H), 8.03 (br, 2H), 8.68 (d, J
175.6, 193.6, 194.1; IR (powder, cm ): 2042 (CO), 1982 (CO);
=
7.0 Hz, 2H, ph), 8.71 (d, J = 4.5 Hz, 1H, β-pyrrole), 8.97 (s, 1H, 21-
UV−vis-NIR (CH Cl , λ /nm, log ε): 359.0 (4.58), 419.0 (4.29),
2
2
max
13
+
H), 9.20 (d, J = 5.5 Hz, 1H, β-pyrrole); C NMR (CDCl , 125 MHz,
ppm): δ 111.9, 113.4, 119.3, 120.9, 122.1, 124.5, 126.1, 126.2, 127.6,
526.0 (4.68), 856.5 (3.42), 949.0 (3.40); HRMS (ESI ): Found: m/z
3
829.14312, calcd for 12C481H31 N4 O4 Ru (MH ): m/z 829.13888;
14
16
102
+
1
1
1
1
28.1, 128.2, 128.3, 128.6, 128.9, 129.4, 129.9, 130.7, 131.2, 132.0,
32.7, 133.3, 135.2, 136.4, 137.6, 137.9, 138.9, 139.1, 140.3, 143.3,
45.2, 148.4, 152.7, 154.0, 154.2, 155.4, 157.8, 163.1, 196.7, 196.7; IR
Anal. calcd for 6b·0.6CH Cl ·0.1C H : C, 66.59; H, 3.65; N, 6.31.
2
2
6
14
Found: C, 66.58; H, 3.90; N, 6.06.
1
6c: H NMR (CDCl , 500 MHz, ppm): δ 1.69 (s, 3H), 7.32 (d, J =
3
−1
(
λ
powder, cm ): 2021 (CO), 1955 (CO); UV−vis-NIR (CH Cl ,
max
4.5 Hz, 1H, β-pyrrole), 7.45 (d, J = 5.0 Hz, 1H, β-pyrrole), 7.53−7.56
(m, 2H), 7.61−7.64 (m, 3H), 7.74−7.78 (m, 5H), 7.82−7.83 (m, 3H),
7.85 (d, J = 4.5 Hz, 1H, β-pyrrole), 7.89 (br, 2H), 8.14−8.16 (m, 4H),
8.66 (d, J = 7.5 Hz, 2H), 8.88 (d, J = 4.5 Hz, 1H, β-pyrrole), 9.25 (d, J
2
2
/nm, log ε): 352.5 (4.60), 413.5 (4.30), 528.0 (4.70), 848.0 (3.43),
+
9
40.0 (3.42); HRMS (ESI ): Found: m/z 847.16180, calcd for
1
2
C521H33 N4 O2 Ru (MH ): m/z 847.16470; Anal. calcd for 5b·
14
16
102
+
1
0
6
.5CH Cl : C, 70.98; H, 3.74; N, 6.31. Found: C, 70.90; H, 4.02; N,
= 4.5 Hz, 1H), 9.32 (s, 1H, 21-H); 13C NMR (CDCl , 125 MHz,
2
2
3
.14.
ppm): δ 22.6, 111.8, 112.4, 119.4, 121.6, 125.2, 126.7, 127.7, 128.0,
128.4, 128.6, 128.7, 129.55, 129.60, 130.0, 130.2, 130.8, 132.1, 132.7,
133.3, 134.9, 136.7, 137.6, 138.1, 138.6, 139.6, 142.5, 144.9, 148.9,
151.0, 151.5, 153.2, 158.3, 164.2, 176.2, 193.1, 193.4; IR (powder,
1
5
c: H NMR (CDCl , 500 MHz, ppm): δ 6.15 (d, J = 6.5 Hz, 2H, o-
3
Phenyl ligand), 6.77 (t, J = 7.5 Hz, 2H, m-Phenyl ligand), 6.83 (t, J =
.5 Hz, 1H, p-Phenyl ligand), 7.18 (d, J = 8.0 Hz, 2H, o-Ph), 7.31 (d, J
7
G
DOI: 10.1021/acs.inorgchem.7b01972
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
−
1
cm ): 2040 (CO), 1980 (CO); UV−vis-NIR (CH Cl , λmax/nm):
The Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, United Kingdom; fax: +44 1223 336033.
2
2
3
9
51.5 (4.58), 418.5 (4.35), 513.5 (4.72), 647.0 (3.63), 847.0 (3.41),
+
34.5 (3.39); HRMS (ESI ): Found: m/z 829.14063, calcd for
1
2
C481H31 N4 O4 Ru (MH ): m/z 829.13888; Anal. calcd for 6c·
14
16
102
+
1
AUTHOR INFORMATION
0
6
.5CH Cl : C, 66.93; H, 3.59; N, 6.44. Found: C, 66.88; H, 3.63; N,
.52.
Synthesis of 6c via the Reaction with Silver Trifluorome-
thanesulfonate. To a toluene (2 mL) solution of 2c (5.2 mg, 6.5
μmol), silver trifluoromethanesulfonate (25 mg, 15 equiv) was added,
and the mixture was stirred for 35 min at room temperature. Then,
potassium acetate (17 mg, 27 equiv) was added, and the temperature
was raised to 100 °C. After 5 h, the solvent was removed under
reduced pressure, and the residue was subjected to the silica gel
column chromatography with 1% methanol/CH Cl . The first red
■
2
2
Corresponding Author
E-mail: hfuruta@cstf.kyushu-u.ac.jp.
*
ORCID
Hiroyuki Furuta: 0000-0002-3881-8807
Notes
The authors declare no competing financial interest.
2
2
fractions afforded 6c (4.9 mg, 92%).
ACKNOWLEDGMENTS
■
Synthesis of 6c with Silver Acetate. To a 1,4-dioxane (2 mL)
solution of 2c (10.0 mg, 12 μmol), silver acetate (23 mg, 10 equiv)
was added, and the mixture was stirred for 22 h at 100 °C. The solvent
was removed under reduced pressure, and the residue was subjected to
the silica gel column chromatography with 1% methanol/CH Cl . The
The work was supported by the Grant-in-Aid (no. 15K13646 to
H.F.; 16K05700 and 17H05377 to M.I.) from the Ministry of
Education, Culture, Sports, Science and Technology of Japan.
The financial support from a bilateral program between JSPS
and the National Research Foundation (NRF) of South Africa
is also acknowledged.
2
2
second red fraction afforded 6c (10.2 mg, 99%).
Ru(NFp)(CO) H (7). To a dry THF solution of N,N-diisopropyl-
2
amine (1 mL, 7.1 mmol) in a Schlenk flask, 1.6 M n-BuLi in hexane
(
0.5 mL, 0.8 mmol) was added at 0 °C under argon, and the solution
REFERENCES
■
was stirred for 1 h. The freshly prepared LDA reagent (1 mL, 1.3
equiv) was then added to 5 mL of THF solution of 2 (100 mg, 0.12
mmol) in a Schlenk flask under N . The resulting solution was heated
at 60 °C for 18 h. After cooling, the reaction mixture was washed with
CH Cl and saturated NH Cl aq, and the organic layer was separated.
After evaporation, the residue was subjected to the silica-gel column
chromatography with CH Cl /Hexane = 1/1 (v/v) as eluent. The first
red fraction afforded a 15.7 mg of crude product. Precipitation from
CH Cl and hexane afforded 4.6 mg of 7c (4.8% yield). 45.9 mg of 2
was recovered.
(
1) Newton, C. G.; Kossler, D.; Cramer, N. Asymmetric Catalysis
Powered by Chiral Cyclopentadienyl Ligands. J. Am. Chem. Soc. 2016,
2
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2
2
(
2
2
1
(
7
c: H NMR (CDCl , 500 MHz, ppm): δ −13.17 (s, 1H, Ru−H),
3
7
7
.31 (t, 2H), 7.46 (t, 1H), 7.56 (q, 1H), 7.58−7.60 (m, 2H), 7.75−
.82 (m, 12H), 8.02 (s, 2H), 8.29 (d, J = 8.0 Hz, 2H, ph), 8.74−8.77
(
m, 3H, β-pyrrole+ph), 9.21 (d, J = 6.0 Hz, 1H, β-pyrrole), 9.38 (s,
(
1
8
H, 21 position H); UV−vis (CH Cl , λmax/nm): 356.5, 523.0, 646.5,
2
2
37.0, 923.0; MALDI-TOF-MS (m/z); 713.942, 1326.008, 1428.180;
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12
14
16
102
1
−1
H) 771.13340; IR (CO/cm ); 1942.9, 2014.3.
Synthesis of 7 with Sodium Borohydride. To a dry THF
solution (10 mL) of 2 (9.9 mg, 12 μmol, 2a: 2b: 2c = 1:3.5:4.3), 2.5
mL of 12 μM THF solution of sodium borohydride (5 equiv) was
added in a Schlenk flask at 0 °C under nitrogen. The solution was
stirred for 15.5 h with 60 °C heating. After cooling, the reaction
mixture was washed with CH Cl and saturated NH Cl aq., and the
2
2
4
II
organic layer was collected. After evaporation, the residue was
Catalyst Precursor, Catalyst, and Intermediate in the Ru -Promoted
subjected to the silica-gel column chromatography with CH Cl /
hexane = 1/1 (v/v) as eluent. The first red fraction afforded 7c in 2.0
mg (21% yield), and 3.0 mg of 2 was recovered.
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Supporting Information
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(
*
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.7b01972.
(
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mentary crystallographic data for this paper. These data can be
obtained free of charge via www.ccdc.cam.ac.uk/data_request/
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2
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000; Vol. 3, Chapter 15, pp 19−21.
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