Rhenium and manganese complexes bearing amino-bis(phosphinite) ligands: Synthesis, characterization, and catalytic activity in hydrogenation of ketones

Article abstract of DOI:10.1021/acs.organomet.8b00020

A series of rhenium and manganese complexes supported by easily accessible and easily tunable amino-bisphosphinite ligands was prepared and characterized by NMR and IR spectroscopy, HR mass spectrometry, elemental analysis, and X-ray diffraction studies. These complexes have been tested in the hydrogenation of ketones. Notably, one of the rhenium complexes, bearing an NH moiety, proved significantly more active than the rest of the series. The reaction proceeds well at 120 °C, under 50 bar of H₂, in the presence of 0.5 mol % of catalyst and 1 mol % of tBuOK. Interestingly, activation of the precatalyst could be followed stepwise by NMR and a rhenium hydride was characterized by X-ray diffraction studies.

Full text of DOI:10.1021/acs.organomet.8b00020

Article
Cite This: Organometallics XXXX, XXX, XXX−XXX
Rhenium and Manganese Complexes Bearing Amino-
Bis(phosphinite) Ligands: Synthesis, Characterization, and Catalytic
Activity in Hydrogenation of Ketones
†
†
†
†
†
Henrion,†
Haoran Li, Duo Wei, Antoine Bruneau-Voisine, Maxime Ducamp, Mickael
̈
†
†
†
is Soule,†
Thierry Roisnel, Vincent Dorcet, Christophe Darcel, Jean-Franco
and Jean-Baptiste Sortais*
̧
is Carpentier, Jean-Franco
̧
́
,†,‡,§
†
Universite
́
de Rennes, CNRS, ISCR-UMR 6226, F-35000 Rennes, France
LCC-CNRS, Universite de Toulouse, CNRS, UPS, Toulouse, France
Institut Universitaire de France, 1 rue Descartes, 75231 Paris Cedex 05, France
S Supporting Information
‡
́
§
*
ABSTRACT: A series of rhenium and manganese complexes
supported by easily accessible and easily tunable amino-
bisphosphinite ligands was prepared and characterized by
NMR and IR spectroscopy, HR mass spectrometry, elemental
analysis, and X-ray diffraction studies. These complexes have
been tested in the hydrogenation of ketones. Notably, one of
the rhenium complexes, bearing an NH moiety, proved
significantly more active than the rest of the series. The reaction proceeds well at 120 °C, under 50 bar of H , in the presence of
2
0
.5 mol % of catalyst and 1 mol % of tBuOK. Interestingly, activation of the precatalyst could be followed stepwise by NMR and
a rhenium hydride was characterized by X-ray diffraction studies.
INTRODUCTION
Chart 1. Representative Rhenium-Based Catalysts (I−V) and
PNP Complexes (III−VI)
■
For several decades, since the discovery of Wilkinson’s catalyst,
the design of homogeneous hydrogenation catalysts has been
based on transition metals belonging to groups 8−10, typically
1
iron, cobalt, nickel, and precious group metals. Comparatively,
hydrogenation catalysts based on group 7 transition metals
2
have been quite elusive. In the case of manganese, hydro-
genation of alkenes, either with molecular dihydrogen or under
water-gas shift and synthesis gas conditions, has been
3
sporadically described until recently. With rhenium, after the
4
5
early work of Ephritikhine and Caulton, the group of Berke
explored the application of a few nitrosyl (poly)-hydride
complexes (e.g., complex I, Chart 1, as a representative
6
example) for the hydrogenation of olefins and nitriles. The
same group also demonstrated that the rhenium analogue
(complex II, Chart 1) of Shvo’s catalyst is active for the
reduction of ketones by transfer hydrogenation, using 2-
7
propanol as hydrogen donor. In addition, Gusev reported the
reduction of acetophenone, by hydrogen transfer, using a
8
PN(H)P nitrosyl rhenium complex (complex III, Chart 1).
However, the association of tridentate PNP ligands and
8
,9
rhenium in coordination chemistry is quite rare and the
catalytic activities of such complexes are quite limited to
been demonstrating a broad versatility with a number of non-
noble transition metals to promote hydrogenation reactions
8
,9i−l,10
date.
In contrast, the application of PNP-Mn complexes
14
15
16
11,17
(
Fe, Co, Ni, Mn
). However, one drawback of these
in hydrogenation and related reactions has seen an impressive
11
explosion in catalysis within only a year.
Among the various tridentate ligands developed, aliphatic
12
Received: January 13, 2018
13
PN(H)P ligands, also called “MACHO” type ligands, have
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.8b00020
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Article
ligands is their high price and relatively low modularity or
difficulty of synthesis.
Recently, we have described the first example of rhenium-
solids in excellent yields after one recrystallization step, and
manganese complexes were obtained as orange powders. Note
that, in the case of ligand 3a and manganese, a black oily crude
product was obtained and could not be purified. All of the
complexes were fairly stable to air and moisture and could be
handled without special precautions; however, they were best
stored under argon in the dark at room temperature.
18
catalyzed hydrogenation of carbonyl derivatives, with a broad
10a
scope and high activity. The catalyst we used (complex V,
C h a r t 1 ) w a s b a s e d o n t h e t y p i c a l b i s -
(
diisopropylphosphinoethane)amine ligand, and we have
shown, with the help of DFT calculations, that the reaction
proceeds through heterolytic cleavage of dihydrogen by a
All the complexes were diamagnetic and were fully
1
13
31
characterized by NMR ( H, C, and P) and IR spectroscopy,
HR mass spectrometry, and elemental analysis. Coordination of
the tridentate ligand was confirmed by the presence of a single
19
metal−ligand cooperative mechanism. Since the development
of cooperative strategies in hydrogenation is of high interest to
20
31
1
develop efficient catalytic systems, we were looking for easily
accessible ligands, with a higher degree of modularity.
With these aims, we turned our attention toward simpler
signal in the P{ H} NMR spectra (for rhenium complexes, δ
128.8, 129.4, and 131.0 ppm for 1b−3b, respectively; for
manganese complexes, δ 174.7 and 172.2 ppm for 1c and 2c,
respectively). In contrast with our previous synthesis of
21
ligands with phosphinite moieties, synthesized in one step
from the readily available corresponding alcohols and
chlorophosphines. In particular, we have been interested in
the application of the amino-bisphosphinite ligand PONOP,
3
complex V and similar PNP and PN P-Mn complexes, for
which cationic tricarbonyl complexes were obtained by
themselves or as a mixture of neutral and cationic compounds,
with this family of PONOP ligands, neutral dicarbonyl
complexes were exclusively obtained, as confirmed by elemental
analysis.
22
initially developed by Stephan. In association with ruthenium
(
complex VI, Chart 1), the hydrogenation of aromatic and
23
aliphatic esters was achieved.
In this contribution, in line with our interest in group 7
The molecular solid-state structures of the five complexes
were also confirmed by single-crystal X-ray diffraction studies.
Representative perspective figures are disclosed in Figures 1−5
24
catalysts for reduction reactions, we have prepared a series of
new rhenium and manganese complexes bearing amino-
bisphosphinite ligands. A comparison of the catalytic activity
in hydrogenation of carbonyl derivatives was achieved, using
catalyst V (Chart 1) as a benchmark.
RESULTS AND DISCUSSION
■
Synthesis of Rhenium and Manganese Complexes.
The three bis-aminobis(phosphinite) ligands 1a−3a, substi-
tuted at the nitrogen by H, Me, and Bn, respectively, were
readily prepared in high yield from the corresponding
diethanolamine and chlorodiisopropylphosphine in THF in
the presence of Et N following literature procedures (Scheme
3
2
2
1).
Scheme 1. Synthesis of PONOP Ligands 1a−3a
Figure 1. Perspective view of the molecular structure of complex 1b
with thermal ellipsoids drawn at 50% probability. Hydrogen atoms,
except NH, are omitted for clarity. The bromide atom is disordered
over two positions, only one of which is depicted.
Rhenium (1b−3b) and manganese (1c−2c) complexes were
synthesized starting from M(CO) Br (M = Re, Mn) and the
5
corresponding ligand by heating at toluene reflux overnight
(Scheme 2). Rhenium complexes were obtained as off-white
Scheme 2. Synthesis of Rhenium (1b−3b) and Manganese
1c−2c) Complexes
(
Figure 2. Perspective view of the molecular structure of complex 2b
with thermal ellipsoids drawn at 50% probability. Hydrogen atoms are
omitted for clarity. Two configurations of the compound are
superimposed in the crystal structure; only one is depicted.
B
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Article
geometry, Tisato and Bolzati have found that in the case of
[
d.
(PN(H)P)ReCl ] meridional coordination is also preferre-
3
9e−g,25
Catalytic Experiments. With these new complexes in
hand, we explored their catalytic activity in the reduction of
ketones with molecular hydrogen (Table 1). On the basis of the
Table 1. Optimization of Reaction Parameters for the
a
Hydrogenation of Acetophenone
Figure 3. Perspective view of the molecular structure of complex 3b,
with thermal ellipsoids drawn at 50% probability. Hydrogen atoms are
omitted for clarity.
cat.
tBuOK
(mol %)
temp
(°C)
time
(h)
conversn
b
entry (mol %) H (bar)
(%)
2
1
2
3
4
5
6
7
8
9
1
1
1
1
1b (1.0)
2b (1.0)
3b (1.0)
1b (1.0)
1b (1.0)
1b (1.0)
1b (1.0)
1b (1.0)
1b (0.5)
1b (0.1)
V (0.5)
30
30
30
50
10
50
50
50
50
50
30
50
50
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
1.0
5.0
1.0
2.0
2.0
110
110
110
110
110
120
100
70
20
20
20
20
20
20
20
20
20
20
16
20
20
87
2
0
90
81
98
80
38
98
93
98
25
20
120
120
70
0
1
2
3
1c (1.0)
2c (1.0)
120
120
a
General conditions: under argon, an autoclave was charged with the
pre)catalyst and toluene (1.0 mL), followed by acetophenone (0.25
Figure 4. Perspective view of the molecular structure of complex 1c,
with thermal ellipsoids drawn at 50% probability. Hydrogen atoms,
except NH, are omitted for clarity.
(
mmol, 29 μL) and tBuOK, in that order. The autoclave was then
b
charged with H and heated in an oil bath. The conversion (%) was
2
1
determined by H NMR on the crude reaction mixture.
optimized conditions defined for the reduction of acetophe-
23
none using complex V, initial experiments were performed on
acetophenone as a model substrate at 110 °C, with 1 mol %
catalyst and 2 mol % tBuOK loadings. Under 30 bar of H2,
(
pre)catalyst 1b bearing a secondary amine led to a promising
conversion of 87% after 20 h of reaction. No reaction occurs
when the catalysts bear a tertiary amine such as in 2b and 3b
(
entries 2 and 3). This clear difference in reactivity is in line
with the importance of NH moieties to promote hydrogenation
via the “classical” cooperative ligand−metal mecha-
nism.
19b−e,20b,26
At 110 °C, the influence of the pressure was limited, as an
increase to 50 bar or decrease to 10 bar only induced minor
variations of the conversion (90 to 81%, Table 1, entries 4 and
Figure 5. Perspective view of the molecular structure of complex 2c,
with thermal ellipsoids drawn at 50% probability. Hydrogen atoms are
omitted for clarity. Two configurations of the compound are
superimposed in the crystal structure; only one is depicted.
5
). On the other hand, the temperature was more crucial to
reach high conversion: from 120 to 70 °C, the conversion
dropped from 98% to 38% over the 20 h reaction time (entries
6−8).
for 1b−3b, 1c, and 2c, respectively. In all cases, the metal lies in
an octahedral environment, the tridentate ligand being in a
meridional coordination mode, and the two carbonyl ligands
are in cis positions. The bromide atom was found randomly in a
cis or trans position with respect to the substituent on the
nitrogen atom. The meridional coordination of the PONOP
ligand contrasts with the facial arrangement observed in
complex V (Chart 1). This isomer corresponds to the most
stable form, in comparison to the facial form according to DFT
Interestingly, the catalyst loading could be reduced by half to
0.5 mol % at 120 °C without apparent degradation of the
activity (Table 1, entry 9 vs entry 6) and even lowered to 0.1
mol % (93% conversion, entry 10), leading to an overall TON
27,28
of 930.
It is worth noting that, with the simpler PONOP ligand, the
same catalytic loading of 0.5 mol % can be reached with 1b as
with complex V based on the PNP ligand, yet at a higher
temperature (120 °C vs 70 °C, Table 1, entry 9 vs 11).
8
,10a
calculations performed by us and others.
In line with this
C
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Article
The manganese complexes were also tested but were found
to be significantly less active: only 25% conversion was
obtained with 1 mol % catalyst at 120 °C under 50 bar of
hydrogen. Surprisingly, the N-Me complex 1c led to nearly the
same conversion as that for the NH complex 2c, which suggests
that the reaction with these Mn complexes may proceed via a
Table 2. Scope of the Hydrogenation of Ketones To Give
Alcohols under the Catalysis of 1b
a
20b,26
different mechanism.
With the optimized conditions in hand (Table 1, entry 9), we
probed the generality of the reaction (Table 2). In general,
from regular aromatic ketones (4a−15a), the corresponding
alcohols (4b−15b) were obtained in good to high yields with
both electron-donating and electron-withdrawing substituents.
The reactivity was noticeably affected by steric hindrance in the
position α to the carbonyl group, as isobutyrophenone and
cyclopropyl phenyl ketone (17a and 18a) were very slowly or
not reduced, respectively, under standard conditions. A cyano
or nitro group at the para position of the aromatic ring also
inhibited the reaction. This lack of reactivity might be
attributed to the weak, yet competitive, coordination abilities
toward the catalyst of such functional groups. Additionally,
heteroaromatic substrates based on thiophene (19a) and
pyridine (20a) were smoothly reduced. Not unexpectedly,
aliphatic, cyclic, and diaryl ketones (21a−26a) required slightly
harsher conditions to be hydrogenated. Most interestingly, the
reaction is chemoselective toward CO, as the remote
trisubtituted CC bond was not hydrogenated (26b). In the
case of benzylideneacetone, as a model of α,β-unsaturated
ketones, the starting material was fully converted into a mixture
of the corresponding unsaturated alcohol (27%) and saturated
alcohol (24%) along with the saturated ketone (49%) as the
major product.
Mechanistic Investigations. In order to get more insights
into the operative mechanism of this rhenium-catalyzed
hydrogenation, a series of experiments in Young-type NMR
31
tubes was conducted (Scheme 3) and followed by P NMR
3
1
1
spectroscopy (Figure 6). First, complex 1b (δ( P{ H}) 128.8
ppm) reacted with KHMDS (2.0 equiv) in toluene-d (the
8
reaction proved more selective with 2 equiv than with 1 equiv;
see Figure S82 in the Supporting Information). The complex
was fully converted at room temperature within a short time
(
typically 1 h) into a new species (1d) displaying a single
1
singlet at δ 156.1 ppm. The H NMR spectrum was consistent
with a highly symmetrical species. Even though single crystals
of compound 1d suitable for X-ray diffraction studies could not
be obtained, one can reasonably assume that the structure of
1
d, resulting from the deprotonation of 1b with the base, is
likely to be a neutral dicarbonyl complex with an amido
9
a,29
ligand.
Upon addition of H (2 bar) inside the NMR tube,
2
complex 1d reacted slowly at room temperature overnight (or
in 1 h at 120 °C; see Figures S83 and S84 in the Supporting
Information) to afford two rhenium hydride species, 1e′ and
1
e″, in the ratio 2:5, exhibiting typical signals in NMR (1e′
31 1 1
δ( P{ H}) 157.8 ppm, δ( H) −2.45 ppm (t, J = 25.9 Hz); 1e″
3
1
1
1
δ( P{ H}) 153.5 ppm, δ( H) −2.07 ppm (t, J = 28.8 Hz)).
The two hydride complexes probably correspond to isomers,
the Re−H bond being presumably either syn or anti to the N−
a
General conditions: under argon, an autoclave was charged with
1
0a,29c,30
complex 1b (0.5 mol %) and toluene (2.0 mL), followed by ketone (2
mmol) and tBuOK (1.0 mol %), in that order. The autoclave was then
H bond.
After the H pressure was released, acetophenone (1.0 equiv)
was charged in the NMR tube. After 18 h at 120 °C, the signals
2
charged with H (50 bar). The mixture was stirred for 18 h at 120 °C
2
1
in an oil bath. The conversion (%) was determined by H NMR on the
of 1e′ and 1e″ disappeared, while concomitantly the character-
crude reaction mixture. Isolated yields (%) are provided in
1
b
c
istic signal of 1d reappeared. In the H NMR spectrum, the
parentheses. 1b (1.0 mol %), tBuOK (2.0 mol %), 130 °C. 1b
d
signal of acetophenone also disappeared. However, the
formation of 1-phenylethanol, resulting from the transfer of
(2.0 mol %), tBuOK (4.0 mol %), 130 °C. 1b (2.0 mol %), tBuOK
(4.0 mol %), 150 °C.
D
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Article
Scheme 3. Stoichiometric Reactions
assume that this isomer corresponds to the more stable form,
and we therefore assigned it as 1e′. 1e″, with the two protons
10a
in a syn configuration would be the active catalytic species.
The epimerization of the N−H bond is likely to occur in the
presence of base or traces of alcohol.
Finally, having identified the NMR signature of the rhenium
hydride complexes, we also confirmed the integrity of the
catalyst after a catalytic run, by running in an autoclave the
hydrogenation of acetophenone with 20 mol % of 1b (and 40
mol % of tBuOK) in toluene-d at 110 °C for 3 h and by
8
analyzing the crude reaction mixture by NMR; this revealed the
sole presence of the two Re−H complexes 1e′ and 1e″ in the
31
1
P{ H} NMR spectrum (see Figures S80 and S81).
CONCLUSION
■
In conclusion, five new complexes based on easily accessible
and easily tunable amino-bisphosphinite ligands have been
prepared and fully characterized. Rhenium complex 1b,
displaying metal−ligand cooperation, is an efficient catalyst
for the hydrogenation of ketones. The reaction proceeds at 120
°
C with the same catalyst load as that for the less affordable
amino-bisphosphine rhenium catalyst V (Chart 1). Interest-
ingly, the reaction could be monitored stepwise by NMR and a
rhenium hydride was isolated and crystallized.
EXPERIMENTAL SECTION
■
General Methods. All reactions were carried out with oven-dried
glassware using standard Schlenk techniques under an inert
atmosphere of dry argon or in an argon-filled glovebox. Toluene,
THF, diethyl ether (Et O), and CH Cl were dried with an MBraun
Figure 6. Monitoring of the stoichiometric reactions described on
Scheme 3 by 31P{ H} NMR spectroscopy, starting from 1b (top), to
1
1
e′ (bottom), via the reaction steps i−v.
2
2
2
MB-SPS-800 solvent purification system and degassed by thaw−freeze
cycles. Technical grade pentane and diethyl ether were used for
column chromatography. Analytical TLC was performed on Merck
the two protons from 1e to the ketone, could not be detected,
likely due to it reacting with excess KHMDS to form an
alkoxide salt insoluble in toluene (note that at the end of the
series of reactions, upon addition of H O, the characteristic
signals of 1-phenylethanol were eventually observed). Finally,
rhenium hydride complexes were regenerated by again
6
0F254 silica gel plates (0.25 mm thickness). Column chromatography
was performed on Acros Organics Ultrapure silica gel (mesh size 40−
0 μm, 60 Å). All reagents were obtained from commercial sources,
6
2
and liquid reagents were dried on molecular sieves and degassed prior
to use. Rhenium pentacarbonyl bromide (98%) and manganese
pentacarbonyl bromide (minimum 98%) were purchased from Strem
Chemicals.
pressurizing the NMR tube under H and heating. Interestingly,
2
1
13
1
after 3 days, a slow isomerization took place, leading exclusively
to 1e′.
H and C{ H} NMR spectra were recorded in CDCl , CD Cl ,
3 2 2
C D , or toluene-d at ambient temperature unless otherwise stated,
6
6
8
Single crystals suitable for X-ray diffraction studies were
obtained for the rhenium hydride complex and revealed the
Re−H and N−H bonds to be in anti positions (Figure 7). We
on Bruker AVANCE 500, AVANCE 400, and AVANCE 300
1
13
spectrometers at 500, 400, and 300 MHz, respectively. H and
C
spectra were calibrated using the residual solvent signal as internal
1
standard ( H, CDCl 7.26 ppm, CD Cl 5.32 ppm, C D 7.16 ppm,
3
2
2
6
6
13
toluene-d 2.08 ppm; C, CDCl 77.16 ppm, CD Cl 53.84 ppm,
8
3
2
2
toluene-d 20.43 ppm, C D 128.06 ppm). IR spectra were measured
8
6
6
with a Shimadzu IR-Affinity 1 instrument with ATR equipment or in
solution. HR-MS spectra and microanalyses were carried out by the
corresponding facilities at the CRMPO (Centre Reg
́
ional de Mesures
Physiques de l’Ouest), University of Rennes 1.
X-ray diffraction data were collected on a D8 VENTURE Bruker
AXS diffractometer equipped with a PHOTON 100 CMOS detector,
using multilayer monochromated Mo Kα radiation (λ = 0.71073 Å) at
T = 150 K. X-ray data are summarized in the Supporting Information.
2
2
Ligands 1a−3a were prepared following literature procedures.
Synthesis of Complexes. Complex 1b: Representative Proce-
dure. Bis(2-((diisopropylphosphino)oxy)ethyl)amine (1a; 0.240
mmol, 80.9 mg, 1.0 equiv) was added to a solution of Re(CO) Br
5
(
0.240 mmol, 97.5 mg, 1.0 equiv) in anhydrous toluene (2 mL). The
mixture was stirred at 100 °C overnight. Toluene was then evaporated.
The crude residue was then recrystallized from dichloromethane (1
mL) and pentane (5 mL) to afford white flake crystals. The white solid
was washed with pentane (2 × 2 mL) to afford the pure compound
(146.5 mg, 93%). Single crystals suitable for X-ray diffraction studies
Figure 7. Perspective view of the molecular structure of complex 1e′,
with thermal ellipsoids drawn at 50% probability. Hydrogen atoms,
except NH and hydride, are omitted for clarity.
E
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were grown by slow diffusion of pentane into a CH Cl solution of 1b
Complex 2c. Following the same procedure as for the synthesis of
complex 1b, starting from 2a (100.0 mg, 0.284 mmol) and
2
2
at room temperature.
1
H NMR (400 MHz, CD Cl ): δ 4.22−4.01 (m, 4H, N-CH ),
Mn(CO)
Br (78.1 mg, 0.284 mmol), complex 2c was obtained as
5
2
2
2
3
2
(
.46−3.28 (m, 2H, CH ), 3.23−3.09 (m, 2H, O-CH ), 3.08−2.98 (m,
an orange solid (124.0 mg, 80%).
iPr
2
1
H, O-CH ), 2.81−2.58 (m, 2H, CH ), 1.40−1.13 (m, 24H, CH
)
H NMR (400 MHz, CD
3.80 (br, 4H, CH ), 3.53−3.38 (br, 2H, CHiPr), 2.91−2.73 (br, 5H,
CHiPr + N-CH ), 1.72−1.61 (br, 2H, CH ), 1.50−1.19 (br m, 24H,
Cl ): δ 61.4 (CH ), 61.3
), 31.5−31.1 (m, 2C, CHiPr), 17.4 (CH3iPr), 16.8
CH ), 16.5 (CH ), 16.4 (CH3iPr) (CO signals not detected).
2
Cl
2
): δ 4.41−4.25 (br s, 2H, CH ), 4.11−
2
2
iPr
3iPr
31
1
note: the NH proton was not observed in the spectrum). P{ H}
2
13
1
NMR (162 MHz, CD Cl ): δ 128.8. C{ H} NMR (101 MHz,
3
2
2
2
13
1
CD Cl ): δ 202.0 (br, CO), 197.2 (br, CO), 66.19 (N-CH ), 58.75 (t,
CH3iPr). C{ H} NMR (75 MHz, CD
(CH ), 46.9 (N−CH
2
2
2
2
2
2
J = 3.4 Hz, O-CH ), 31.76 (t, J = 17.9 Hz, CH ), 29.55 (t, J = 11.6 Hz,
2
3
2
iPr
(
CH ), 18.92 (t, J = 2.7 Hz, CH3iPr), 18.33 (CH3iPr), 17.81 (t, J = 2.1
3iPr
3iPr
iPr
3
1
1
P{ H} NMR (162 MHz,CD Cl ): δ 172.2. Anal. Calcd for
Hz, CH3iPr), 16.43 (CH3iPr). Anal. Calcd for C H NO BrP Re: C,
2
2
18
37
4
2
3
2.78; H, 5.65; N, 2.12. Found: C, 32.53; H, 5.60; N, 2.06. HR MS
C
19 4 2 2 2
H39NO BrP Mn·CH Cl : C, 38.30; H, 6.59; N, 2.23, Found: C,
+
79
187
+
(
ESI): m/z [M + Na] calcd for C H NO BrNaP2 Re 682.0831,
38.21; H, 6.48; N, 2.88. HR-MS (ESI): m/z [M − Br] calcd for
C H39NO P Mn 462.1729, found 462.1737 (2 ppm); m/z [M]
19 4 2
calcd for C H NO BrP Mn 541.09127, found 541.0912 (0 ppm);
1
8
37
4
+
187
4 2
+.
found 682.0824 (1 ppm); m/z [M − Br] calcd for C H NO P Re
18
37
79
−1
5
1
80.1755, found 580.1749 (0 ppm). IR (ν, cm , CH Cl ): 1929,
19 39
4
2
2
2
+
.
79
m/z [M − 2CO] calcd for C H NO Br P Mn 485.10144, found
840.
Complex 2b. Following the same procedure as for the synthesis of
complex 1b, starting from 2a (100.0 mg, 0.284 mmol) and Re(CO) Br
17 39
2
2
−
1
29
4
85.1015 (0 ppm). IR (ν, cm , CH Cl ): 1946, 1923, 1842.
2 2
NMR-Scale Synthesis of Complex 1d. In a Young-type NMR tube,
complex 1b (8.4 mg, 0.012 mmol) was added to a solution of KHMDS
4.8 mg, 0.024 mmol) in dry toluene-d8 (ca. 0.5 mL) at room
temperature. NMR spectra were recorded after 1 h of reaction.
5
(
(
115.6 mg, 0.284 mmol), complex 2b was obtained as a white solid
(
174.6 mg, 92%).
1
H NMR (400 MHz, CD Cl ): δ 4.46−4.33 (m, 2H, N-CH ),
2
2
2
1
H NMR (400 MHz, C D ): δ 3.77−3.68 (br m, 4H, CH ), 2.45 (br
4
.33−4.21 (m, 2H, O-CH ), 4.14−3.97 (m, 2H, N-CH ), 3.40−3.27
m, 2H, CH ), 3.01 (s, 3H, N-CH ), 2.87−2.72 (m, 2H, CH ), 1.96
7
8
2
2
2
s, 4H, CH ), 2.30−2.21 (m, 4H, CH ), 1.25−1.11 (m, 24H, CH ).
P{ H} NMR (162 MHz C D ): δ 156.1. C{ H} (101 MHz, C D ):
(
(
2
iPr
3iPr
iPr
3
iPr
31
1
13
1
dd, J = 13.6, 3.8 Hz, 2H, O-CH ), 1.39−1.14 (m, 24H, CH ).
7
8
7
8
2
3iPr
1
3
1
δ 207.3 (t, J = 6.2 Hz, CO), 74.3 (t, J = 3.8 Hz, CH ), 63.9 (t, J = 7.8
C{ H} NMR (101 MHz, CD Cl ): δ 199.8 (br, CO), 198.4 (br CO),
2
2
2
Hz, CH ), 31.8 (br s, CH ), 17.1 (br s, CH3iPr), 16.7 (br s, CH3iPr).
2
iPr
6
4.0 (N-CH ), 63.2 (t, J = 3 Hz, O-CH ), 50.7 (N-CH ), 32.7 (t, J = 13
2
2
3
NMR-Scale Synthesis of Complexes 1e′ and 1e″. The NMR tube
Hz, CH ), 31.6 (t, J = 17 Hz, CH ), 18.5 (t, J = 2 Hz, CH3iPr), 18.2
iPr
iPr
31
1
containing the solution of 1d in toluene-d , obtained in the previous
8
(
t, J = 2 Hz, CH3iPr), 18.0 (CH3iPr), 17.2 (CH3iPr). P{ H} NMR (162
step, was pressurized with H (2 bar). NMR spectra were recorded
2
MHz, CD Cl ): δ 129.4. Anal. Calcd for C H NO BrP Re: C, 33.88;
2
2
19 39
4
2
after 18 h of reaction at room temperature. Single crystals suitable for
X-ray diffraction studies were obtained by slow evaporation in the
H, 5.84; N, 2.08, Found: C, 33.84; H, 5.94; N, 2.16. HR-MS (ESI): m/
+
79
187
z [M + Na] calcd for C H NO BrNaP2 Re 696.0993, found
19
39
4
+
79
187
glovebox.
6
7
1
96.0983 (1 ppm); m/z [M + K] calcd for C H NO BrKP2 Re
12.07269, found 712.0714 (2 ppm). IR (ν, cm , CH Cl ): 1925,
834. IR (ν, cm , ATR): 1911, 1822.
Complex 3b. Following the same procedure as for the synthesis of
complex 1b, starting from 3a (100.0 mg, 0.234 mmol) and Re(CO) Br
19 39 4
1
−1
Complex 1e′. H NMR (400 MHz, toluene-d
8
): δ 3.74−3.65 (m,
2
2
−1
2H), 3.40−3.30 (m, 2H), 2.38−2.29 (m, 2H), 2.20−2.10 (m, 4H),
.84−1.79 (m 2H), 1.43−1.25 (m, 24H), −2.45 (t, J = 25.9 Hz, 1H).
1
3
1
1
13
1
P{ H} NMR (162 MHz, toluene-d ): δ 157.8. C{ H} NMR (101
8
5
MHz, toluene-d ): δ 67.2, 56.8 (t, J = 3 Hz), 33.9 (t, J = 14 Hz), 33.3
8
(
(
95.0 mg, 0.234 mmol), complex 3b was obtained as a white solid
(
t, J = 16 Hz), 18.6 (t, J = 3 Hz), 18.1 (t, J = 2 Hz), 17.9, 17.6 (CO
163.6 mg, 93%).
1
signals were not detected).
H NMR (400 MHz, CD Cl ): δ 7.43−7.27 (m, 3H, H ), 7.07−
2
2
Ar
1
Complex 1e″. H NMR (400 MHz, toluene-d ): δ 3.57−3.47 (m,
8
7
.02 (m, 2H, H ), 4.82 (s, 2H, CH -C H ), 4.75−4.57 (m, 2H, N-
Ar
2
6
6
2
H), 3.23−3.15 (m, 2H), 2.38−2.29 (m, 2H), 2.20−2.10 (m, 4H),
.84−1.79 (m 2H), 1.43−1.25 (m, 24H), −2.07 (t, J = 28.8 Hz, 1H).
P{ H} NMR (162 MHz, toluene-d ): δ 153.5.
CH ), 4.21−4.01 (m, 2H, N-CH ), 3.86 (dd, J = 13.5, 9.8 Hz, 2H, O-
2
2
1
CH ), 3.40 (dhept, J = 14.1, 7.1 Hz, 2H, CH ), 2.96−2.81 (m, 2H,
31
1
2
iPr
8
CH ), 2.25 (dd, J = 14.3, 4.9 Hz, 2H, O-CH ), 1.58−1.13 (m, 24H,
iPr
2
31
1
13
1
General Procedure for Hydrogenation Reactions. In an
CH ). P{ H} NMR (162 MHz, CD Cl ): δ 131.0. C{ H} NMR
3
iPr
2
2
argon-filled glovebox, an autoclave was charged with complex 1b
6.6 mg, 0.5 mol %) and toluene (2.0 mL), followed by ketone (2
(
101 MHz, CD Cl ): δ 199.6 (br t, J = 7 Hz, CO), 198.7 (br t, J = 7
2 2
(
Hz, CO), 132.1 (C ), 129.09 (C ), 129.06 (C ), 64.0(N-CH ), 61.4
Ar
Ar
Ar
2
mmol) and tBuOK (2.2 mg, 1.0 mol %), in that order. The autoclave
(
CH -C H ), 56.1 (t, J = 2 Hz, O-CH ), 33.0 (t, J = 12 Hz, CH ),
2 6 6 2 iPr
was then charged with H (50 bar). The mixture was stirred for 20 h at
2
3
1
1.7 (t, J = 17 Hz, CH ), 18.7 (t, J = 2 Hz, CH3iPr), 18.11 (CH3iPr),
8.06 (t, J = 2 Hz, CH3iPr), 17.5 (CH3iPr). Anal. Calcd for
iPr
1
20 °C in an oil bath. The solution was then diluted with ethyl acetate
(2.0 mL) and filtered through a small pad of silica (2 cm in a Pasteur
C H NO BrP Re: C, 40.05; H, 5.78; N, 1.87, Found: C, 39.77; H,
2
5
43
4
2
pipet). The silica was washed with ethyl acetate (5 mL). The filtrate
was evaporated, and the crude residue was purified by column
+
.
5
.88; N, 1.87. HR-MS (ESI): m/z [M]
calcd for
7
9
187
C H NO BrP2 Re 749.1408, found 749.1391 (2 ppm). IR (ν,
2
5
43
4
chromatography (SiO , petroleum ether/ethyl acetate mixture as
−
1
−1
2
cm , CH Cl ): 1925, 1834. IR (ν, cm , ATR): 1932, 1832.
2
2
eluent). For specific conditions, see the main article. For the
characterization of the product of the catalysis, see the Supporting
Information.
Complex 1c. Following the same procedure as for the synthesis of
complex 1b, starting from 1a (100.0 mg, 0.296 mmol) and
Mn(CO) Br (81.4 mg, 0.296 mmol), complex 1c was obtained as
5
an orange solid (129.5 mg, 82%.)
1
ASSOCIATED CONTENT
H NMR (400 MHz, CD Cl ): δ 4.30−3.85 (m, 4H, CH ), 3.66−
■
2
2
2
3
1
2
.32 (m, 2H, CH ), 3.24−2.92 (m, 3H, NH+ CH ), 2.81 (dd, J =
*
S
Supporting Information
iPr
2
0.4, 3.1 Hz, 2H, CH ), 2.75−2.62 (m, 2H, CH ), 1.47−1.14 (m,
2
iPr
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.8b00020.
13
1
4H, CH3 ). C{ H} NMR (101 MHz, CD Cl ): δ 64.8 (CH ), 57.4
iPr
2
2
2
(
1
br, CH ), 31.4−31.1 (m, 2C, CH ), 18.3 (br, CH ), 17.9 (CH ),
2
iPr
3iPr
3iPr
31 1
7.6 (br, CH3 ), 16.5 (br, CH ) (CO signals not detected). P{ H}
iPr 3iPr
NMR spectra giving characterization of complexes and
products of catalysis and X-ray data tables (PDF)
NMR (162 MHz, CD Cl ): δ 174.7. Anal. Calcd for
2
2
C H NO BrP Mn: C, 40.92; H, 7.06; N, 2.65, Found: C, 40.82;
1
8
37
4
2
+
.
H, 6.73; N, 2.42. HR-MS (ESI): m/z [M] calcd for
7
9
Accession Codes
CCDC 1815476−1815481 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
C H NO BrP Mn 527.0756, found 527.0754 (0 ppm); m/z [M
1
8
37
4
2
+
.
79
−
2CO] calcd for C H NO BrP Mn 471.08579, found 471.0854
1 ppm). IR (ν, cm , CH Cl ): 1953, 1927, 1846.
1
6
37
2
2
−1
31
(
2 2
F
DOI: 10.1021/acs.organomet.8b00020
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
charge via www.ccdc.cam.ac.uk/data_request/cif, or by email-
ing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
Catalysis: [ReBrH(NO)(labile ligand)(large-bite-angle diphosphine)]
Complexes as Highly Active Catalysts in Olefin Hydrogenations. J. Am.
Chem. Soc. 2011, 133, 8168−8178. (d) Rajesh, K.; Dudle, B.; Blacque,
O.; Berke, H. Homogeneous Hydrogenations of Nitriles Catalyzed by
Rhenium Complexes. Adv. Synth. Catal. 2011, 353, 1479−1484.
(
e) Jiang, Y.; Huang, W.; Schmalle, H. W.; Blacque, O.; Fox, T.; Berke,
AUTHOR INFORMATION
Corresponding Author
E-mail for J.-B.S.: jean-baptiste.sortais@lcc-toulouse.fr.
■
*
H. Efficient Lewis Acid Promoted Alkene Hydrogenations Using
Dinitrosyl Rhenium(−I) Hydride Catalysts. Organometallics 2013, 32,
7043−7052. (f) Jiang, Y.; Schirmer, B.; Blacque, O.; Fox, T.; Grimme,
S.; Berke, H. The “Catalytic Nitrosyl Effect”: NO Bending Boosting
the Efficiency of Rhenium Based Alkene Hydrogenations. J. Am. Chem.
Soc. 2013, 135, 4088−4102.
ORCID
Haoran Li: 0000-0002-6022-5936
Duo Wei: 0000-0002-5928-3151
Antoine Bruneau-Voisine: 0000-0002-0984-3261
(7) Landwehr, A.; Dudle, B.; Fox, T.; Blacque, O.; Berke, H.
Bifunctional Rhenium Complexes for the Catalytic Transfer-Hydro-
Mickael
Jean-Franco
Jean-Baptiste Sortais: 0000-0003-1178-8588
Notes
̈
Henrion: 0000-0001-8682-5182
genation Reactions of Ketones and Imines. Chem. - Eur. J. 2012, 18,
5
701−5714.
8) Choualeb, A.; Lough, A. J.; Gusev, D. G. Hydridic Rhenium
Nitrosyl Complexes with Pincer-Type PNP Ligands. Organometallics
007, 26, 3509−3515.
9) (a) Radosevich, A. T.; Melnick, J. G.; Stoian, S. A.; Bacciu, D.;
̧
is Soule:
́
0000-0002-6593-1995
(
2
(
The authors declare no competing financial interest.
Chen, C.-H.; Foxman, B. M.; Ozerov, O. V.; Nocera, D. G. Ligand
Reactivity in Diarylamido/Bis(Phosphine) PNP Complexes of Mn-
ACKNOWLEDGMENTS
We thank the Centre National de la Recherche Scientifique
■
(
CO) and Re(CO) . Inorg. Chem. 2009, 48, 9214−9221. (b) Ozerov,
3
3
O. V.; Huffman, J. C.; Watson, L. A.; Caulton, K. G. Conversion of
Ethylene to Hydride and Ethylidyne by an Amido Rhenium
Polyhydride. Organometallics 2003, 22, 2539−2541. (c) Ozerov, O.
V.; Watson, L. A.; Pink, M.; Caulton, K. G. Transformation of Acyclic
Alkenes to Hydrido Carbynes by (PNPR)Re Complexes. J. Am. Chem.
Soc. 2004, 126, 6363−6378. (d) Ozerov, O. V.; Watson, L. A.; Pink,
M.; Caulton, K. G. Operationally Unsaturated Pincer/Rhenium
Complexes Form Metal Carbenes from Cycloalkenes and Metal
Carbynes from Alkanes. J. Am. Chem. Soc. 2007, 129, 6003−6016.
(e) Porchia, M.; Tisato, F.; Refosco, F.; Bolzati, C.; Cavazza-Ceccato,
M.; Bandoli, G.; Dolmella, A. New Approach to the Chemistry of
(
CNRS), the Universite
́
de Rennes 1, Fonds Europee
́
ns de
Dev
́
eloppement Economique Regional (FEDER founds),
́
INCREASE FR-CNRS 3707, European Commission as part
of H2020-RIA project COSMOS (grant 635405), l’Institut
Universitaire de France (IUF) and the Agence Nationale de la
Recherche (ANR agency, program JCJC ANR-15-CE07-0001
“
Ferracycles”).
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