Synthesis of the cyclopentadienone rhodium complexes and investigation of their catalytic activity in the reductive amination of aldehydes in the presence of carbon monoxide

Article abstract of DOI:10.1016/j.jorganchem.2017.02.014

Reaction of bis(p-tolyl-propargyl)-tosylamide with [(cod)RhCl]₂in the presence of CO gives the cyclopentadienone complex [(Cpd’)Rh(CO)Cl]_n(Cpd’ = TsN(CH₂)₂C₄(Tol)₂CO). Its dissolution in DM

Full text of DOI:10.1016/j.jorganchem.2017.02.014

Accepted Manuscript
Synthesis of the cyclopentadienone rhodium complexes and investigation of their
catalytic activity in the reductive amination of aldehydes in the presence of carbon
monoxide
Roman A. Pototskiy, Oleg I. Afanasyev, Yulia V. Nelyubina, Denis Chusov, Alexander
R. Kudinov, Dmitry S. Perekalin
PII:
S0022-328X(17)30085-2
10.1016/j.jorganchem.2017.02.014
JOM 19803
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 1 October 2016
Revised Date: 9 February 2017
Accepted Date: 11 February 2017
Please cite this article as: R.A. Pototskiy, O.I. Afanasyev, Y.V. Nelyubina, D. Chusov, A.R. Kudinov,
D.S. Perekalin, Synthesis of the cyclopentadienone rhodium complexes and investigation of their
catalytic activity in the reductive amination of aldehydes in the presence of carbon monoxide, Journal of
Organometallic Chemistry (2017), doi: 10.1016/j.jorganchem.2017.02.014.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

Synthesis of the cyclopentadienone rhodium complexes and investigation of their catalytic
ACCEPTED MANUSCRIPT
activity in the reductive amination of aldehydes in the presence of carbon monoxide
Roman A. Pototskiy, Oleg I. Afanasyev, Yulia V. Nelyubina,
Denis Chusov, Alexander R. Kudinov,† Dmitry S. Perekalin,*
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28
Vavilova st., Moscow, 119991, Russian Federation. E-mail: dsp@ineos.ac.ru
† deceased
Abstract
Reaction of bis(p-tolyl-propargyl)-tosylamide with [(cod)RhCl]2 in the presence of CO gives the
cyclopentadienone complex [(Cpd’)Rh(CO)Cl]n (Cpd’ = TsN(CH2)2C4(Tol)2CO). Its dissolution
in DMSO or pyridine leads to decarbonylation and formation of the adducts
(Cpd’)Rh(DMSO)2Cl and (Cpd’)Rh(Py)2Cl. The reaction of [(Cpd’)Rh(CO)Cl]n with AgPF6 and
p-xylene produces the sandwich arene complex [(Cpd’)Rh(p-xylene)]PF6, in which the arene can
t
be substituted by BuNC ligand to give [(Cpd’)Rh(tBuNC)3]PF6. The arene complex acts as an
efficient catalyst for the reductive amination of carbonyl compounds in the presence of CO as
deoxygenation agent, producing various amines in 75-85% yields.
Keywords: Carbon monoxide / Cyclopentadienone / Diyne / Rhodium / Reductive amination
1. Introduction
Diene rhodium complexes, such as [(cod)RhCl]2, are widely used in organometallic
synthesis and catalysis [1,2]. On the other hand, the related cyclopentadienone rhodium
complexes, such as [(C4Ph4CO)RhCl]2, have been much less studied [3,4]. This is, partly,
because such compounds are usually prepared from [(C2H4)2RhCl]2 and free cyclopentadienones,
which are readily available only with bulky aryl substituents. However, recently Chatani et al.
have reported an example of alternative approach, namely the high-yield synthesis of the
cyclopentadienone rhodium complex [{(CH2)3C4Ph2CO}Rh(CO)Cl]2 from 1,7-diphenyl-1,6-
heptadiyne, [(сod)RhCl]2 and CO [5,6]. This route potentially allows one to prepare a number of
cyclopentadienone complexes with various substituents.
Recently, we have developed a novel approach for the reductive amination of aldehydes
and ketones, which employs carbon monoxide as the only reducing agent [7,8,9] (Scheme 1).
The most active catalysts for this reaction discovered so far are the diene and cyclobutadiene
rhodium complexes [10]. On the other hand the classical reductive amination is known to
1

proceed in the presence of ruthenium cyclopentadienone complexes (e.g. Shvo catalyst
ACCEPTED MANUSCRIPT
[(C4Ph4CO)Rh(CO)2]2H2) [11]. Therefore we have become interested in the synthesis of the
cyclopentadienone rhodium complexes and their application in reductive amination. Herein we
report the results of this investigation.
Scheme 1. Previously reported reductive amination in the presence of CO.
2. Results and Discussion
As a ligand source we chose N,N-bis(p-tolyl-propargyl)-tosylamide (1), which was
synthesized following the published procedure in two steps from tosylamide, propargyl bromide
and p-iodotoluene [12]. Tolyl substituents (designated as Tol) were purposely used instead of
1
more common phenyl groups in order to obtain more informative H NMR spectra of the
compounds. Following the approach of Chatani et al. [5], we reacted the diyne 1 with
[(cod)RhCl]2 under CO atmosphere (1 bar from balloon) to obtain the cyclopentadienone
complex [(Cpd’)Rh(CO)Cl]n (2) in 70−80% yield (Cpd’ = substituted cyclopentadienone =
TsN(CH2)2C4(Tol)2CO, see Scheme 2). It is interesting to note, that analogous reactions with the
terminal diyne N,N-bis(propargyl)tosylamide or with the internal mono-alkyne 3-hexyne did not
give cyclopentadienone complexes. The product 2 precipitated from the reaction mixture
capturing some amount of the starting diyne 1, which decreased the yield of 2. Compound 2 was
insoluble in common organic solvents so the admixture of 1 was removed simply by washing the
product with hot nitromethane. Low solubility of 2 apparently is caused by the formation of
oligomers with Rh−Cl and Rh−OC bridges [3a]. The degree of oligomerization of 2 remains
unknown and, in fact, may be variable.
Scheme 2. Synthesis of the cyclopentadienone rhodium complex.
2

Dissolution of complex 2 in dimethyl sulfoxide or pyridine led to decarbonylation
ACCEPTED MANUSCRIPT
(clearly visible in IR spectra) and formation of bis-adducts (Cpd’)Rh(DMSO)2Cl (3) and
(Cpd’)Rh(Py)2Cl (4) in ca. 90% yield (Scheme 3). These compounds were much more soluble
than 2 and therefore were expected to have more reproducible catalytic behavior. Noteworthy,
the cyclopentadienone rhodium chloride 2 readily forms the 18 valence-electron bis-ligand
adducts 3 and 4, while the related diene complex [(cod)RhCl]2 produces only the 16 valence-
electron mono-adduct (cod)Rh(py)Cl with pyridine [13] (the reaction of [(cod)RhCl]2 with
DMSO does not give a stable adduct even with one DMSO molecule [14]). This tendency was
noted previously for [(C4Ph4CO)RhCl]n complexes [3a]. The reluctance of cyclopentadienone
rhodium complexes to form 16 valence-electron species may affect their catalytic activity.
Reaction of the chloride complex 2 with AgPF6 and p-xylene gave the arene complex
[(Cpd’)Rh(p-xylene)]PF6 (5) in 60% yield. As a close analogue of the cyclobutadiene complex
[(C4Et4)Rh(p-xylene)]PF6 this compound was expected to undergo facile replacement of p-
xylene to give the catalytically active half-sandwich complexes [15]. Indeed, addition of p-
anisidine to the solution of 5 in acetone-d6 led to displacement of p-xylene and formation of the
1
tentative solvate species [(Cpd’)Rh(NH2C6H4OMe)x]PF6 (according to H NMR), which,
however, could not be isolated. On the other hand, the reaction of 5 with a stronger ligand tBuNC
gave the stable half-sandwich complex [(Cpd’)Rh(tBuNC)3]PF6 (6), which was isolated in 72%
yield.
Tol
Tol
TsN
O
TsN
O
L
Tol
Cl
Tol
Cl
Rh
Rh
L
CH2Cl2
L
OC
n
L = DMSO (3), Pyridine (4)
2
p-xylene
AgPF6
CH3NO2
Tol
Tol
Tol
TsN
O
PF6
TsN
O
tBuNC
Tol
–
–
Rh+
Rh+
PF6
CNtBu
CH2Cl2
tBuNC
tBuNC
5
6
Scheme 3. Ligand substitution in the cyclopentadienone rhodium complexes.
3

All the compounds obtained were stable in air, both in solution and the solid state. They
ACCEPTED MANUSCRIPT
1
13
were characterized by IR spectra, H and C NMR spectra (except the insoluble 2), as well as
elemental analysis. The structures of 3, 4 and 5 were established by X-ray diffraction (Figures 1,
2 and 3). The geometry of Cpd’ ligand is similar for the complexes 3−5 and is notably different
from the free cyclopentadienone C4Ph4CO [16]. In particular, C=C double bonds are elongated
upon coordination with rhodium (average length 1.431 Å in 3−5 vs. 1.348 Å in C4Ph4CO). At the
same time C=O bond length in 3−5 (average 1.225 Å) is similar to that in C4Ph4CO (1.211 Å)
suggesting only minor participation of the ketone group of Cpd’ in bonding with metal [17]. It
may be also noted, that DMSO ligand in the complex 3 shows strong trans-influence, which
leads to elongation of Rh1−C7 bond (2.224(5) Å) compared to the formally equivalent Rh−C2
bond (2.181(4) Å).
Fig. 1. The structure of complex 3 in 50% thermal ellipsoids. Only one of two independent
molecules is shown. The solvate molecules and the hydrogen atoms are omitted for clarity.
Selected interatomic distances (Å): Rh1−C1 2.436(4), Rh1−C2 2.181(4), Rh1−C3 2.145(4),
Rh1−C6 2.173(4), Rh1−C7 2.224(5), Rh1−S2 2.3200(12), Rh1−S3 2.3613(12), Rh1−Cl1
2.4222(12).
4

ACCEPTED MANUSCRIPT
Fig. 2. The structure of complex 4 in 50% thermal ellipsoids. The solvate molecules and the
hydrogen atoms are omitted for clarity. Selected interatomic distances (Å): Rh1−C1 2.382(7),
Rh1−C2 2.150(7), Rh1−C3 2.106(7), Rh1−C6 2.090(7), Rh1−C7 2.140(7), Rh1−N1S 2.144(5),
Rh1−N2S 2.112(6), Rh1−Cl1 2.3981(19).
Fig. 3. The structure of complex 5 in 50% thermal ellipsoids. The counter-ion and the hydrogen
atoms are omitted for clarity. Selected interatomic distances (Å): Rh1−C1 2.433(3), Rh1−C2
2.188(3), Rh1−C3 2.131(3), Rh1−C6 2.127(3), Rh1−C7 2.209(3), Rh1−C22 2.290(3), Rh1−C23
2.288(3), Rh1−C24 2.276(3), Rh1−C25 2.279(3), Rh1−C26 2.282(3), Rh1−C27 2.274(3),
Rh···C6(plane) 1.793.
5

We investigated the catalytic activity of the complexes 2−6 for the model reaction of p-
ACCEPTED MANUSCRIPT
tolylaldehyde with p-anisidine in the presence of carbon monoxide as a reducing agent (Scheme
4; Table 1). At 90 °C and 30 bar pressure of CO the p-xylene complex 5 (1 mol% loading)
produced the target amine 7 in only 32% yield. However, at 120 °C the yield reached reasonable
80%. Further increase of the temperature did not increase the yield of the product 7 but resulted
in additional formation of the double alkylated amine 7’ (entries 3−4). The amount of 7’ can be
reduced by using the excess of p-anisidine; however, we preferred to run the process with a near
stoichiometric ratio of the reactants and therefore fixed the temperature at 120 °C. Additional
tests shown that CO pressure can be decreased from 30 bar to 5 bar without compromising the
yield, while further decrease to 3 and 1 bar significantly slowed down the reaction (entries 5−7).
The catalyst loading can be decreased to 0.5 mol% but not to 0.1 mol% (entries 8−9). In overall,
the catalytic activity of the complex 5 was close to that of the state-of-the-art catalyst
[(C4Et4)Rh(p-xylene)]PF6 (entries 8 vs. 10), although the latter can operate at more mild
conditions (3 bar of CO, 90 °C) [10a]. Other cyclopentadienone rhodium complexes 2−4 and 6
shown very low activity (entries 11-14) presumably because CO was not able to displace the
t
strong ligands like Cl or BuCN. This correlates with the previously observed low catalytic
activity of some other chloride complexes, such as [(cod)RhCl]2 and [Cp*RhCl2]2 [10a].
The detailed mechanism of the reductive amination is so far unclear. However, we found
t
that the reaction proceeds in BuOH solution, which ruled out the transfer hydrogenation
mechanism involving oxidation of an alcohol solvent to an aldehyde.
Scheme 4. Catalytic reductive amination.
6

Table 1. Optimization of reaction conditions for the reductive amination of p-tolualdehyde with
ACCEPTED MANUSCRIPT
p-anisidine in the presence of carbon monoxide as the reducing agent.a
Entry Catalyst
(loading)
CO pressure, Temperature, Yield of the
bar
30
30
30
30
5
°C
product 7
32%
1
2
5 (1 mol%)
5 (1 mol%)
5 (1 mol%)
5 (1 mol%)
5 (1 mol%)
5 (1 mol%)
5 (1 mol%)
90
120
140
160
120
120
120
120
120
120
80%
3
75% (7’, 12%)
66% (7’, 18%)
81%
4
5
6
3
44%
7
1
9%
8
5 (0.5 mol%) 30
5 (0.1 mol%) 30
83%
9b
10
51%
[(C4Et4)Rh(p- 30
xylene)]PF6
85%
(0.5 mol%)
11
12
13
14
2 (1 mol%)
3 (1 mol%)
4 (1 mol%)
6 (1 mol%)
5
5
5
5
120
120
120
120
4%
3%
2%
2%
a Reaction conditions: p-anisidine (15 mg, 0.12 mmol), p-tolylaldehyde (14 µL, 0.12 mmol), 100
µL of ethanol, 4 hours. Yields were determined by gas chromatography. b in 24 hours.
We briefly investigated the reaction scope using several challenging substrates and 1
mol% loading of the catalyst 5. It was found that the reductive amination of
cyclohexanecarboxaldehyde, which is prone to aldol condensation, smoothly gives the amine 8
in 75% isolated yield (Scheme 4). Acetone, which is much less reactive than aldehydes, also
produced the amine 9 in a good yield 84%. Finally, the reaction of tolylaldehyde with a
secondary aliphatic dibenzylamine gave the target product 10 in 80% yield.
7

HN
ACCEPTED MANUHSNCRIPT
OMe
OMe
6, 78%
8, 75%
HN
N
OMe
9, 84%
10, 80%
Scheme 4. Various amines synthesized by the catalytic reductive amination
(isolated yields are given).
3. Conclusion
In overall, it can be concluded that the cyclopentadienone rhodium complexes can be
conveniently synthesized from [(cod)RhCl]2, CO and the readily available 1,6-diynes. Unlike the
diene congeners, these cyclopentadienone complexes prefer 18 valence-electron configuration
instead of 16 valence-electron. Nevertheless, such complexes can be active and thermally stable
catalysts for the reductive amination of aldehydes in the presence of CO.
4. Experimental section
4.1. General
Unless otherwise noted all reactions were carried out under ambient atmosphere in
anhydrous solvents, which were purified and dried using standard procedures. 1H and 13С NMR
spectra were measured with a Bruker Avance 400 spectrometer at 20°C. The chemical shifts are
reported relative to redisual signals of the solvent (for CHCl3: 7.26 1H, 77.16 13C; for CHD2NO2:
1
4.33 H, 62.80 13C) Infrared spectra (IR) were measured with Shimadzu IRPrestige-21
spectrometer. Gas chromatography analysis was carried out using Chromatec Crystal 5000.2
apparatus (helium as career gas, flow rate 1.6 ml/min; yields were calculated using calibration
curve). Complex [(cod)RhCl]2 [18] and diyne 1 [12] were synthesized according to the published
procedure. NMR spectra of the compounds are given in the supplementary data.
8

4.2. Synthesis of [(Cpd’)Rh(CO)Cl]n (2)
ACCEPTED MANUSCRIPT
CO was bubbled through a stirred solution of [(cod)RhCl]2 (50 mg, 0.1 mmol) and diyne 1 (86
mg, 0.2 mmol) in 1,2-dichloroethane (4 ml) for 1 hour at 50 °C (the reaction at room temperature
gave lower yield 68%). Then the flow of CO was stopped and the dark red mixture was stirred
for additional 3 days at room temperature under CO atmosphere (balloon attached) to ensure
complete precipitation of the product. The orange precipitate of 2 was collected by centrifugation
and washed with CH2Cl2 (3×5 ml). The solid was heated in nitromethane (15 ml) for 30 minutes
to dissolve admixture of 1, then nitromethane was decanted, the residue was washed again with
CH2Cl2 (3×5 ml) and dried in vacuum to give complex 2 as orange solid (103 mg, 83% yield).
Due to extremely low solubility of 2 the NMR spectra were measured in DMSO-d6 solution,
which led to formation of complex 3 (vide infra). FT-IR (vaseline oil, cm−1): 2059 (metal bonded
CO), 1666 cm−1 (carbonyl group of Cpd’ ligand). Anal. Calc. for C29H25O4SNRhCl: C 56.00, H
4.05, N 2.25; found: C 55.94, H 3.91, N 2.29. Does not melt or decompose up to 230 °C.
4.3. Synthesis of (Cpd’)Rh(DMSO)2Cl (3)
DMSO (100 µl, excess) was added to a suspension of complex 2 (31 mg, 0.05 mmol) in CH2Cl2
(2 ml) and the mixture was stirred for 2 hours at 30 °C in order to dissolve all the precipitate. The
resulting solution was evaporated to dryness in vacuum, the residue was washed with Et2O (2×3
ml), dissolved in chloroform (2 ml) and precipitated by a mixture of Et2O/petroleum ether (1:1,
10 ml) to give 3 as red powder, which was dried in vacuum (35 mg, 93% yield). Crystals for X-
ray diffraction analysis were grown by slow diffusion of Et2O vapors into solution of 3 in CHCl3.
1H NMR (400 MHz, CDCl3 + 5% DMSO-d6): δ = 7.88 (d, J = 8.2 Hz, 4H, Tol), 7.83 (d, J = 8.3
Hz, 2H, Ts), 7.25 (d, J = 8.3 Hz, 2H, Ts), 7.08 (d, J = 8.2 Hz, 4H, Tol), 4.96 (d, J = 13.4 Hz, 2H,
CH2), 4.13 (d, J = 13.4 Hz, 2H, CH2), 2.53 (s, 12H, DMSO), 2.31 (s, 3H, Ts), 2.18 (s, 6H, Tol).
The spectra in CDCl3 without DMSO-d6 additive shown a second set of signals, presumably, due
to partial dissociation of DMSO ligands. This second set disappeared upon addition of DMSO-
d6. 13C NMR (101 MHz, CDCl3 + 5% DMSO-d6): δ = 166.7 (CO of Cpd’), 143.1, 138.2, 133.5,
129.4, 129.2, 127.5, 127.2, 127.0, 47.0 (CH2), 21.0 (Tol), 20.9 (Ts). The signals of the
coordinated carbon atoms were not observed. FT-IR (vaseline oil, cm−1): 1626 (carbonyl group
of Cpd’ ligand). Anal. Calc. for C32H37ClNO5S3Rh: C 51.23, H 4.97, N 1.87; found: C 50.60, H
4.84, N 1.67. Decomposes without melting at about 200 °C.
4.4. Synthesis of (Cpd’)Rh(Py)2Cl (4)
Pyridine (1 ml) was added to a suspension of complex 2 (62 mg, 0.1 mmol) in CH2Cl2 (2 ml) and
the mixture was stirred for 2 hours at 30 °C in order to dissolve all the precipitate. The solution
was then placed into 10 ml vial and the product was crystallized by diffusion of Et2O vapors into
9

solution. The red rhombic crystals were collected, washed with petroleum ether (3×5 ml) and
ACCEPTED MANUSCRIPT
dried to give 4 (69 mg, 92% yield). Crystals for X-ray diffraction analysis were grown by slow
diffusion of Et2O vapors into solution of 4 in CH2Cl2 with a small additive of pyridine (to
prevent possible dissociation).
1H NMR (400 MHz, CDCl3): δ = 8.30 (br.s, 4H, Py), 7.92 (d, J = 7.9 Hz, 2H, Ts), 7.71 (d, J =
7.8 Hz, 4H, Tol), 7.63 (br.s, 2H, Py), 7.41 (d, J = 7.9 Hz, 2H, Ts), 7.09 (br.s, 4H, Py), 6.99 (d, J
= 7.8 Hz, 4H, Tol), 4.53 (d, J = 12.5 Hz, 2H, CH2), 3.95 (d, J = 12.5 Hz, 2H, CH2), 2.47 (s, 3H,
Ts), 2.18 (s, 6H, Tol). The signals of pyridine ligands are broad, which may indicate their
hindered rotation or partial dissociation. 13C NMR (101 MHz, CDCl3): δ = 162.3 (CO of Cpd’),
151.7 (Py), 144.0, 137.5 (Py), 137.0, 134.4, 130.1, 129.7, 129.6, 127.9, 127.1, 125.1 (Py), 94.0
(coordinated C), 63.5 (coordinated C), 48.2 (CH2), 21.7 (Ts), 21.5 (Tol). FT-IR (vaseline oil,
cm−1): 1602 (carbonyl group of Cpd’ ligand), 1570, 1520. Anal. Calc. for
C38H35ClN3O3SRh×CH2Cl2: C 55.96, H 4.46, N 5.02; found: C 55.43, H 4.82, N 4.30.
Decomposes without melting at about 180 °C.
4.5. Synthesis of [(Cpd’)Rh(p-xylene)]PF6 (5)
Under argon atmosphere a mixture of complex 2 (100 mg, 0.16 mmol), AgPF6 (41 mg, 0.16
mmol), p-xylene (400 µl, 3.2 mmol) and nitromethane (1 ml) was vigorously stirred for 12 hours
at 50 °С. The mixture was then opened to air, the precipitate was removed by centrifugation and
the red solution was evaporated. The residue was dissolved in CH2Cl2 (2 ml) and yellow product
was precipitated by Et2O (15 ml). The precipitate was washed Et2O (2×5 ml), dissolved again in
CH2Cl2 (2 ml) and crystallized by diffusion of Et2O vapor to give 5 as orange crystals, which
were dried in vacuum (78 mg, 60% yield). Crystals for X-ray diffraction analysis were grown by
slow diffusion of Et2O vapors into solution of 5 in acetone with a small additive of p-xylene (to
prevent possible dissociation).
1H NMR (400 MHz, CD3NO2): δ = 7.94 (d, J = 8.1 Hz, 4H, Tol), 7.88 (d, J = 8.0 Hz, 2H, Ts),
7.56 (d, J = 8.0 Hz, 2H, Ts), 7.36 (d, J = 8.1 Hz, 4H, Tol), 6.49 (s, 4H, p-xylene), 4.89 (d, J =
14.2 Hz, 2H, CH2), 4.47 (d, J = 14.2 Hz, 2H, CH2), 2.48 (s, 3H, Ts), 2.39 (s, 6H, Tol), 1.80 (s,
6H, p-xylene). 13C NMR (101 MHz, CD3NO2): δ = 166.0 (CO of Cpd’), 147.0, 143.6, 134.0,
131.7, 131.5, 130.3, 129.3, 126.0, 117.8, 107.5 (coordinated C of p-xylene), 103.3 (coordinated
C of Cpd’), 85.2 (coordinated C of Cpd’), 55.3, 50.0, 21.8, 21.7, 17.50. The coordinated
substituted carbon atom of p-xylene was not observed. FT-IR (vaseline oil, cm−1): 1648
(carbonyl group of Cpd’ ligand). Anal. Calc. for C36H35F6NO3PSRh: C 53.41, H 4.36, N 1.73;
found: C 53.48; H 4.74; N 1.67. Decomposes without melting at about 200 °C.
10

4.6. Synthesis of [(Cpd’)Rh(tBuNC)3]PF6 (6)
ACCEPTED MANUSCRIPT
t
Under argon atmosphere a solution of complex 5 (24 mg, 0.03 mmol) and BuNC (12 µL, 0.1
mmol) in СH2Cl2 (1 ml) was for 12 hours. The mixture was then opened to air, and the product
was crystallized by diffusion of Et2O vapor into the solution to give 6 as yellow needle crystals,
which were dried in vacuum (22 mg, 72% yield).
1H NMR (400 MHz, CDCl3): δ = 7.85 (d, J = 8.2 Hz, 4H, Tol), 7.63 (d, J = 8.3 Hz, 2H, Ts), 7.44
(d, J = 8.3 Hz, 2H, Ts), 7.18 (d, J = 8.2 Hz, 4H, Tol), 4.77 (d, J = 16.2 Hz, 2H, CH2), 4.33 (d, J =
16.2 Hz, 2H, CH2), 2.46 (s, 3H, Ts), 2.33 (s, 6H, Tol), 1.45 (s, 27H, (Me)3C). 13C NMR (101
MHz, CDCl3): δ = 172.2 (CO of Cpd’), 146.1, 139.1, 134.1, 130.5, 129.8, 127.7, 127.5, 127.3,
104.6, 59.7, 49.1 (CH2), 30.0 (t-Bu), 21.7 (Tol), 21.6 (Ts). FT-IR (vaseline oil, cm−1): 1641,
1654 (carbonyl group of Cpd’ ligand), 2199, 2221 (isonitrile). Anal. Calc. for
C43H52F6N4O3PRhS: C 54.20, H 5.50, N 5.88; found: C 53.80, H 5.36, N 5.78.
4.7. General procedure for catalytic experiments
A glass vial in a 10 mL stainless steel autoclave was charged with prescribed amount of the
catalyst, the solvent, the amine and the carbonyl compound. The use of a glass vial is crucial:
interaction of the catalyst with the metal surface of the autoclave can leads to decreased catalytic
activity. The autoclave was sealed, flushed three times with 10 bar of CO, and then charged with
the indicated pressure of CO. The reactor was placed into a preheated oil bath. After the
indicated time, the reactor was cooled to room temperature and depressurized. The residue was
dissolved in dichloromethane, passed through a short layer of silica gel and analyzed by GC and
1H NMR. Further purification was achieved by column chromatography using hexane/ethyl
acetate mixtures as eluent. Experimental details for each particular amine are given in the
supplementary data.
4.8. X-ray crystallography
Data for single crystals of 3×4CHCl3 and 5 were collected at 120 K with a Bruker APEX2
diffractometer, while those for 4×0.5C5H5N×0.5CH2Cl2 with a Bruker APEX2 DUO
diffractometer, using graphite monochromated Mo-Kα radiation (λ = 0.71073 Å, ω-scans). They
were integrated with the program SAINT and then scaled, merged and corrected for Lorentz-
polarization effects. Note that the best available crystal for 3×4CHCl3 was twinned, so indexing
with the Cell_Now software [19] was needed to describe this twinning as a superposition of two
components. The structure of 3×4CHCl3 structure was then refined using HKLF5 instruction and
additional scale factor (BASF instruction). Semi-empirical absorption correction from
equivalents was applied using the package SADABS [20] (for 4×0.5C5H5N×0.5CH2Cl2 and 5) or
TWINABS [21] (for 3×4CHCl3). The structures were solved by the direct method and refined by
11

the full-matrix least-squares against F2 in anisotropic approximation for non-hydrogen atoms.
ACCEPTED MANUSCRIPT
The positions of hydrogen atoms were calculated, and they were refined in isotropic
approximation in riding model. All calculations were performed using the SHELXTL PLUS 5.0
software [22].
5. Acknowledgments
We thank Dr. A.A. Pavlov and Dr. E.I. Gutsul for recording NMR and IR spectra, and Dr. D.V.
Muratov for stimulating discussions. The work was financially supported by the Russian Science
Foundation (grant # 16-13-10393).
Appendix A. Supplementary data
CCDC 1505673 contains the supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Appendix B. Supplementary data
Supplementary data associated with this article can be found online.
Graphical abstract
Graphical abstract synopsis
Cyclopentadienone rhodium complex was prepared from [(cod)RhCl]2, 1,6-diyne and CO. This
complex catalyzed the reductive amination of aldehydes in the presence of carbon monoxide, as
the only reducing agent.
12

Highlights
ACCEPTED MANUSCRIPT
A series of cyclopentadienone rhodium complexes were synthesized from a 1,6-dyine.
Unlike diene congeners, cyclopentadienone complexes prefer 18-VE configuration.
These complexes show good catalytic activity in hydrogen-free reductive amination.
References
1
For some recent examples see: a) S.D. Pike, F.M. Chadwick, N.H. Rees, M.P. Scott, A.S.
Weller, T. Krämer, S.A. Macgregor, J. Am. Chem. Soc. 137 (2015) 820;
b) R. Savka, H. Plenio, Dalton Trans. 44 (2015) 891;
c) S. Siangwata, N. Baartzes, B.C.E. Makhubela, G.S. Smith, J. Organomet. Chem. 796 (2015)
26;
d) L. Oehninger, L.N. Küster, C. Schmidt, A. Muñoz-Castro, A. Prokop, I. Ott, Chem. Eur. J. 19
(2013) 17871;
e) I. Mena, E. A. Jaseer, M.A. Casado, P. García-Orduña, F.J. Lahoz, L.A. Oro, Chem. Eur. J. 19
(2013) 5665;
2
For some reviews on catalytic application see: a) P. Tian, H.-Q. Dong, G.-Q. Lin, ACS
Catalysis 2 (2012) 95;
b) C. Defieber, H. Grützmacher, E.M. Carreira, Angew. Chem. Int. Ed. 47 (2008) 4482.
3 For synthesis see: a) D. Rechavi, R. Scopelliti, K. Severin, Organometallics 27 (2008) 5978;
b) H.K. Gupta, N. Rampersad, M. Stradiotto, M. J. McGlinchey, Organometallics 19 (2000) 184;
c) N.A. Bailey, V.S. Jassal, R. Vefghi, C. White, J. Chem. Soc., Dalton Trans. (1987) 2815;
d) S. Mcvey, P.M. Maitlis, J. Organomet. Chem. 19 (1969) 169;
e) S. McVey, P.M. Maitlis, Can. J. Chem. 44 (1966) 2429.
4 For catalytic application see: a) S. Kusumoto, M. Akiyama, K. Nozaki, J. Am. Chem. Soc. 135
(2013) 18726;
b) L. Quebatte, R. Scopelliti, K. Severin, Angew. Chem. Int. Ed. 43 (2004) 1520;
c) S. Gauthier, R. Scopelliti, K. Severin, Organometallics 23 (2004) 3769.
5 S.I. Lee, Y. Fukumoto, N. Chatani, Chem. Commun. 46 (2010) 3345.
6 It should be also noted that some free cyclopentadienones can be prepared from 1,6-diynes and
CO, see: a) Y. Xu, J. Zhao, H. Chen, W. Wu, H. Jiang, Chem. Commun. 50 (2014) 2488;
b) T. Shibata, K. Yamashita, E. Katayama, K. Takagi, Tetrahedron 58 (2002) 8661.
7 a) D. Chusov, B. List, Angew. Chem. Int. Ed. 53 (2014) 5199;
b) P.N. Kolesnikov, D.L. Usanov, E.A. Barablina, V.I. Maleev, D. Chusov, Org. Lett. 16 (2014)
5068;
c) P.N. Kolesnikov, N.Z. Yagafarov, D.L. Usanov, V.I. Maleev, D. Chusov, Org. Lett. 17 (2015)
173;
13

ACCEPTED MANUSCRIPT
d) N.Z. Yagafarov, P.N. Kolesnikov, D.L. Usanov, V.V. Novikov, Y.V. Nelyubina, D. Chusov,
Chem. Commun. 52 (2016) 1397.
8
a) For the state of the art review on reduction by CO via the water-gas shift reaction see: A.
Ambrosi, S.E. Denmark, Angew. Chem. Int. Ed. 55 (2016) 12164;
b) J.W. Park, Y.K. Chung, ACS Catal. 5 (2015) 4846;
c) S.S. Li, X. Liu, Y.M. Liu, H.Y. He, K.N. Fan, Y. Cao, Chem. Commun. 50 (2014) 5626;
d) S.E. Denmark, Z.D. Matesich, J. Org. Chem. 79 (2014) 5970;
e) J. Ni, L. He, Y. Cao, H.Y. He, K.N. Fan, Chem. Commun. 47 (2011) 812.
9 For examples of other applications of carbon monoxide as a reducing agent see:
a) H.-Q. Li, X. Liu, Q. Zhang, S.-S. Li, Y.-M. Liu, H.-Y. He, Y. Cao, Chem. Comm. 51 (2015)
11217;
b) F. Ragaini, S. Cenini, E. Gallo, A. Caselli, S. Fantauzzi, Curr. Org. Chem. 10 (2006) 1479;
c) A.M. Tafesh, J. Weiguny, Chem. Rev. 96 (1996) 2035.
10
a) O.I. Afanasyev, A.A. Tsygankov, D.L. Usanov, D.S. Perekalin, N.V. Shvydkiy, V.I.
Maleev, A.R. Kudinov, D. Chusov, ACS Catal. 6 (2016) 2043;
b) N.V. Shvydkiy, E.A. Trifonova, A.M. Shved, Y.V. Nelyubina, D. Chusov, D.S. Perekalin,
A.R. Kudinov, Organometallics 35 (2016) 3025.
11
a) B.L. Conley, M.K. Pennington-Boggio, E. Boz, T.J. Williams, Chem. Rev. 110 (2010)
2294;
b) R. Karvembu, R. Prabhakaran, K. Natarajan, Coord. Chem. Rev. 249 (2005) 911;
c) C.P. Casey, G.A. Bikzhanova, Q. Cui, I.A. Guzei, J. Am. Chem. Soc. 127 (2005), 14062 and
references therein;
d) See also a recent review on related cyclopentadienone iron complexes: A. Quintard, J.
Rodriguez, Angew. Chem. Int. Ed. 53 (2014) 4044.
12 T. Xu, Q. Yang, W. Ye, Q. Jiang, Z. Xu, J. Chen, Z. Yu, Chem. Eur. J. 17 (2011) 10547.
13 J. Rajput, A.T. Hutton, J.R. Moss, H. Su, C. Imrie, J. Organomet. Chem. 691 (2006) 4573.
14 R. Dorta, H. Rozenberg, L.J.W. Shimon, D. Milstein, Chem. Eur. J. 9 (2003) 5237.
15
D.S. Perekalin, N.V. Shvydkiy, Y.V. Nelyubina, A.R. Kudinov, Chem. Eur. J. 21 (2015)
16344.
16 J.C. Barnes, W.M. Horspool, F.I. Mackie, Acta Cryst. C 47 (1991) 164.
17
For comparison: single C−OH bond length is 1.378 Å in the hydroxycylcopentadienyl
complex (C4Ph4COH)IrH2(PtBu2Me). See ref. 4a.
18 G. Giordano, R.H. Crabtree, Inorg. Synth. 28 (1990) 88.
19
G.M. Sheldrick. CELL_NOW (version 2008/4). Georg-August-Universität Göttingen,
Göttingen, Germany, 2008.
20 SADABS. Bruker AXS Inc., Madison, Wisconsin, USA, 2001.
21 TWINABS. Bruker AXS Inc., Madison, Wisconsin, USA, 2001.
22 G.M. Sheldrick, Acta Cryst. A 64 (2008) 112.
14