Highly active phosphine-free bifunctional iron complex for hydrogenation of bicarbonate and reductive amination

Article abstract of DOI:10.1002/chem.201500720

Based on a "transition metal frustrated Lewis pair" approach, a cyclopentadienone iron tricarbonyl complex has been designed and applied in the reductive amination and hydrogenation of bicarbonate. This well-defined phosphine-free complex displays the best activities reported to date for an iron complex in the reduction of bicarbonate into formate and in reductive amination.

Full text of DOI:10.1002/chem.201500720

DOI: 10.1002/chem.201500720
Communication
&
Hydrogenation
Highly Active Phosphine-Free Bifunctional Iron Complex for
Hydrogenation of Bicarbonate and Reductive Amination
Trieu-Tien Thai,[a] Delphine S. Mꢀrel,[a] Albert Poater,*[b] Sylvain Gaillard,[a] and Jean-
Luc Renaud*[a]
tuning the steric and electronic properties of the iron tricar-
Abstract: Based on a “transition metal frustrated Lewis
bonyl complex, we endeavor to improve the catalytic activity.
pair” approach,
a cyclopentadienone iron tricarbonyl
Indeed, considering the 16-electron intermediate with its cyclo-
pentadienone ligand, the vacant site of the iron metal center
and one lone pair of the carbonyl moiety of the ligand can be
assimilated to a frustrated Lewis pair.[9] Ligand modifications
may thus improve the catalytic activity of such cyclopentadi-
enone iron tricarbonyl complexes. Toward this goal, two series
of iron complexes have been envisaged; one based on the
modification of the acidic character of the metal center (via
the introduction of more p-acidic ligands L) and one based on
the variation of the Lewis-basic character of the carbonyl
framework located on the cyclopentadienone (Figure 1). As
carbonyl ligands are the most p-acidic ligands, we focused our
complex has been designed and applied in the reductive
amination and hydrogenation of bicarbonate. This well-
defined phosphine-free complex displays the best activi-
ties reported to date for an iron complex in the reduction
of bicarbonate into formate and in reductive amination.
Economic constraints and environmental concerns in chemistry
have led to increased demand for the replacement of noble
metals used in chemical processes by Earth-abundant ones.
Iron-catalyzed reduction of polarized C=X bonds and carbonic
derivatives has received intensive attention and some iron
complexes have shown activities and selectivities that are com-
petitive with those of noble metals.[1,2] However, exchanging
noble metals for cheap, abundant, and biocompatible iron
complexes to perform reduction is not the sole criterion to
render such complexes attractive for industrial applications;[3]
the catalytic activities and the price of the ligand must also be
taken into account. In the context of developing more active
and selective iron complexes, the group of Beller[4] and our
group[5,6] recently demonstrated that variation of the nature of
the substituent on cyclopentadienone iron tricarbonyl complex
(Knçlker’s type complex)[7,8] improved not only the reactivity
but also the chemoselectivity and permitted reduction of unsa-
turated aldehydes, as well as reductive amination. Thus, we
showed that not only does the steric hindrance of the silyl
group prevent the dimerization of the iron complex and
improve its catalytic activity, but the presence of heteroatom
on the backbone of the cyclopentadienone also participates in
stabilizing the 16-electron iron species.[5b] However, despite
these promising results, further improvements are required to
make such bifunctional iron complexes more competitive. By
Figure 1. Cyclopentadienone iron tricarbonyl complexes: a) Transition metal
frustrated Lewis pairs; b) the cyclopentadienone tricarbonyl iron(0)
complexes used in this study.
attention on the second hypothesis. Herein we report the syn-
thesis of 3,4-ethylenediamino-substituted cyclopentadienone
iron tricarbonyl complexes and their application in reductive
amination and in hydrogenation of bicarbonate.
[a] Dr. T.-T. Thai, D. S. Mꢀrel, Dr. S. Gaillard, Prof. Dr. J.-L. Renaud
Laboratoire de Chimie Molꢀculaire et Thioorganique, UMR 6507, INC3M, FR
3038, ENSICAEN-University of Caen ,14050 Caen (France)
Fax: (+33)231452877
To enhance the Lewis base character of the cyclopentadi-
enone iron tricarbonyl complex, we synthesized N,N’-dimethyl
3,4-ethylenediamino-substituted cyclopentadienone to act as
a ligand.[10] Following the reported procedure,[10a] the ligand 4
was prepared in two steps, from diethyl oxalate and 1,3-diphe-
nylpropan-2-one, in 65% overall yield (Scheme 1). The complex
5 was then obtained in 69% yield by simple heating of the
dienone 4 with [Fe2(CO)9] in toluene (Scheme 1).
E-mail: jean-luc.renaud@ensicaen.fr
[b] Dr. A. Poater
Departament de Quꢁmica,Institut de Quꢁmica Computacional i Catꢂlisi
(IQCC), University of Girona, Campus de Montilivi, 17071 Girona, Catalonia
(Spain)
E-mail: albert.poater@udg.edu
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201500720.
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Communication
and 7 in a model reaction be-
tween citronellal and N-methyl-
benzylamine under 5 bar of
hydrogen in ethanol at 858C
(Scheme 2).[5b] Gratifyingly,
5
gave the best yield (23, 67, and
83% for complexes 6, 7 and 5,
respectively; Scheme 2).
Scheme 1. Synthesis of 3,4-ethylenediamino-substituted cyclopentadienone tricarbonyl iron(0) complex 5.
Reaction conditions: i) Na, EtOH, ethyl glyoxalate (2), 08C then RT, 48h; ii) N,N’-dimethylethylenediamine, MeOH, D,
2 h; iii) [Fe2(CO)9] (2 equiv.), toluene, D, overnight.
To unambiguously establish the atom connectivity in com-
plex 5, single crystals were grown by slow diffusion of pentane
in dichloromethane. Suitable single crystals were obtained and
subjected to X-ray diffraction (XRD; Figure 2). This structure
presented a C2 symmetry with a slight distortion of the pipera-
Scheme 2. Reductive amination catalyzed by complexes 5, 6, and 7.
Whereas a threshold temperature of 858C and catalyst load-
ing of 5 mol% appeared necessary with complex 6 or 7 to
ensure efficient reductive amination and to avoid side-product
formation, we delineated the optimized reaction conditions
(catalyst loading and temperature) with 5. Whereas no conver-
sion was reached at room temperature, reductive amination
proceeded to completion at 448C in the presence of only
2.5 mol% of complex 5. A decreased catalyst loading of
1 mol% provided 50% conversion at 448C. All of these results
demonstrated that not only the prevention of dimerization of
unsaturated iron intermediates by the twisted phenyl rings
(highlighting further that steric hindrance around the metal
center is a crucial requirement), but also the higher electron
density on the cyclopentadienone moiety improves the
efficiency of this transition metal frustrated Lewis pair.
Figure 2. Crystal structures of of complex 5 (left) and 6 (right). Thermal ellip-
soids are depicted at 50% probability level. Hydrogen atoms are omitted for
clarity.
zine-type ring. However, the most remarkable feature of this
complex is that the phenyl rings and the cyclopentadienone
ancillary ligand are not coplanar, unlike in the complex 6 (Fig-
ures 1 and 2).[5b] Both phenyl rings in complex 5 are almost
perpendicular to the cyclopentadienone (see Table 2 and
Table S1 in the Supporting Information). The rotation of the
phenyl rings seems to be due to the N-methyl substituents. As
we have reported previously that steric hindrance around the
metal center prevented the formation of a stable and inactive
dimer and ensured higher catalytic activities,[5b] we hypothe-
sized that such rotation might change the catalytic properties
of the iron species.
The scope of the reductive amination catalyzed by 5 and
comparison with that catalyzed by 7 are summarized in Table 1
(5 mol% of catalyst was used to ensure good conversions with
all substrates). With the exception of the reaction between cit-
ronellal and tetrahydroisoquinoline (Table 1, entry 1), yields
were higher with 5 than with 7, regardless of the identity of
the carbonyl compounds and the primary or secondary ali-
phatic amines. More importantly, although aromatic amines
did not furnish any alkylated product with 7, we were pleased
to isolate in 51% yield the amine from the reductive amination
between citronellal and p-anisidine in the presence of 5
(Table 1, entry 3). Improved yields were also obtained from less
reactive aromatic aldehydes, such as 4-nitro-, 4-fluoro-, or 2-
methoxybenzaldehyde (Table 1, entries 4–7), although some
competitive direct reduction of the carbonyl derivatives was
observed (e.g., Table 1, entry 5; the amine/alcohol ratio was
70:30 with 5, whereas with 7 it was 35:65). The hindered
ketone norcamphor also reacted smoothly with tetrahydroiso-
quinoline and the corresponding amine was isolated in 70%
yield. The corresponding yield was much lower with 7
(23%;Table 1, entry 9).
To investigate the electron density on the cyclopentadie-
none moiety in 5 compared to Knçlker’s complex 7 (Figure 1),
the CO-bond IR stretching frequencies and the bond lengths
of the carbonyl ligands were investigated for both complexes.
The experimentally measured values validated the initial hy-
pothesis that the electron density was higher on the cyclopen-
tadienone moiety in 5. The CO stretching frequencies were at
2061, 2053 and 1987 cmÀ1 in complex 7 (see the Supporting
Information of ref. [5b]), whereas they were 2027, 1962 and
1947 cmÀ1 in 5, indicating a more significant back donation
and thus a more significant electron density on the Fe center
(see the Supporting Information). Based on the analysis of the
CIF files of 5 and 7,[8] the same trends can be drawn. All of the
CO ligand bond lengths are longer in complex 5, indicating
again a more significant electron density on the Fe center.
The catalytic activities of complex 5 were first evaluated in
reductive amination and compared with those of complexes 6
DFT calculations for the reductive amination with complex 5
were undertaken and compared to those with complex 7 to
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lower energy barrier with 5 appears to be due to a more facile
H transfer to the C=O group of the cyclopentadienone ligand,
thanks to a shorter H···O distance. Indeed, by comparison of
the intermediates III for the two complexes, the calculated
H···O(=C) distances is 0.105 ꢂ shorter with 5 than with 7. The
reduction pathway (IV to VI) is another key feature of this en-
ergetic diagram as the thermodynamic stability of species IV
and VI led to an exothermicity of 3.5 kcalmolÀ1 for 5 whereas
an endothermicity of 2.8 kcalmolÀ1 was calculated for 7.
Overall, the DFT calculations provide clues to explain both the
milder reaction conditions and the higher catalytic
performance of catalyst 5 with respect to 7.
Based on these results and thanks to the enhanced
efficiency, we thought that 5 might also be able to reduce less
polarized double bonds, such as carbon dioxide or carbonates.
Reduction of carbon dioxide offers new opportunities for the
synthesis of methanol or formic acid, two important C1 build-
ing blocks in synthesis.[11] Although the cleavage of HÀH bonds
requires more energy than that of SiÀH or BÀH bonds, from an
industrial point of view and in term of atom economy, the
most appealing reducing agent is molecular hydrogen. Howev-
er, due to the lower electrophilic character of the carbonyl
function, research into carbon dioxide hydrogenation has to
date made little progress,[2] despite great industrial interest in
this exciting challenge. The groups of Laurenczy and
Beller,[12,13] Milstein,[14] and Gonsalvi[15] have all recently dis-
closed well-defined iron hydride complexes for the reduction
of carbon dioxide into formate or formamides, which hydro-
genated bicarbonate was to give formate with turnover num-
bers (TONs) of up to 727,[12] 7546,[13] 320,[14] and 1229,[15] respec-
tively. Although these complexes have paved the way to new
reactivities in iron chemistry, they contain electron-rich, air-
and moisture sensitive, and expensive phosphorus ligands.
Therefore, we envisaged that our cyclopentadienone iron tri-
carbonyl complex could provide an alternative iron catalyst for
the hydrogenation of bicarbonate (Table 2).
Table 1. Iron-catalyzed reductive amination.
Entry Carbonyl deriva- Amine
Yield [%] with Yield [%]
5[a,c]
tive
with 7[b,c]
1[d]
2[d]
3[d]
81
46
51
83
38
N.R.
4[e]
5[e]
6[e]
48
41
68
16
29
23
7[e]
8[e]
9[e]
66
72
70
21
68
23
[a] Conditions: Carbonyl derivative (1 mmol), amine (1.2 mmol), complex
5 (5 mol%), Me3NO (5 mol%), and H2 (5 bar) in alcohol at 448C; [b] condi-
tions: Carbonyl derivative (1 mmol), amine (1.2 mmol), complex
(5 mol%), Me3NO (5 mol%), and H2 (5 bar) in alcohol at 858C; [c] yield of
7
isolated product; [d] in ethanol; [e] in methanol with NH4PF6 (10 mol%).
We initially chose water as the solvent because bicarbonate
is water-soluble and reduction with cyclopentadienyl iron com-
plexes can operate in this solvent.[6] Sodium formate was ob-
tained with a TON of 8.5 at 1008C under 10 bar of hydrogen
((Table 2, entry 1). An increase in the pressure to 50 bar en-
hanced the reactivity (Table 2, entry 2). To further improve the
reactivity, several parameters were evaluated, including the sol-
vent and the temperature (Table 2, entries 3, 5, and 6). Again,
compared to complex 5, Knçlker’s complex 7 showed lower
activities (Table 2, entries 3 vs. 4). High TONs were attained in
alcoholic solvent (Table 2, entries 3–7; see also the Supporting
Information). However, the highest activity was obtained in
a 1:1 solvent mixture of DMSO and water; a TON of 1246 was
attained at 1008C under 50 bar of hydrogen (Table 2, entry 13).
Notably, the reduction could be carried out without Me3NO as
activator and furnished better results (Table 2, entries 8–12).[16]
This result represented the best activity reported to date with
a phosphine free iron complex and is competitive with some
of the previously reported cases.[12–15]
gain additional information on the catalytic cycle and to eluci-
date its improved performances.[17] The energy profile of the
reductive amination was obtained according to the previously
reported mechanism (Figure 3; for the energy diagram for the
reaction with complex 7, see the Supporting Information).[5b]
The energy profiles for oxidative removal of one CO followed
by hydrogen coordination (intermediate I to III) and for coordi-
nation and hydrogenation of the imine (intermediate IV to VI)
are quite similar for complexes 5 and 7. The low energy barrier
for H2 coordination (5.8 kcalmolÀ1) impedes the potential
dimerization of intermediate II (the dimer is 12.5 kcalmolÀ1
higher in energy than II). Overall, the third step (III to IV, corre-
sponding to hydrogen activation and hydrogen cleavage)
seems to be the rate-determining step, with an energy barrier
of 25.4 kcalmolÀ1 (Figure 4). This barrier is 3.4 kcalmolÀ1 higher
in energy with catalyst 7 (see the Supporting Information)
than with complex 5. From a structural point of view, this
In summary, we have synthesized and fully characterized
a well-defined phosphine-free iron complex bearing a more
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Communication
bonate. Amines were obtained
in moderate to high yields under
very mild reaction conditions.
Formate was also obtained from
bicarbonate with TONs up to
1246 under mild reaction condi-
tions. Further work will be dedi-
cated to extending the applica-
tion of such transition metal
frustrated Lewis pair to the acti-
vation of hydrogen and other
small molecules in the presence
of various unsaturated com-
pounds.
Experimental Section
General conditions for the hydro-
genation of bicarbonate: In an
autoclave, to a mixture of iron
complex (5 or 7; 0.01 mmol),
Me3NO (0.01 mmol), and NaHCO3
(5 mmol), the degassed solvent
(5 mL) was added under argon at-
mosphere. The autoclave was pres-
surized with molecular hydrogen
to the desired pressure and heated
at the desired temperature under
stirring for 20 h. After 20 h, the au-
toclave was cooled down to room
temperature, the reactor was
vented, and 1H NMR spectroscopy
(in D2O with DMF as internal stan-
dard) of the crude reaction mixture
was used to measure the yield of
reaction.
Figure 3. Energy profile for 5-catalyzed reduction of imine (energies in kcalmolÀ1). For a 3D representation of the
structures with relevant distances, see the Supporting Information.
Table 2. Iron-catalyzed hydrogenation of bicarbonate.[a]
Acknowledgements
Entry
S/C[a]
500
500
500
500
500
500
500
Solvent
H2O
PH [bar]
T [8C]
Me3NO
Conv. [%][b]
TON[c]
2
We gratefully acknowledge fi-
nancial support from the “Minis-
tꢃre de la Recherche et des Nou-
velles Technologies” for a PhD
grant for D.S.M., CNRS (Centre
National de la Recherche Scienti-
fique), the “Rꢀgion Basse-Nor-
mandie”, the “CRUNCH” interre-
gional network and the Europe-
an Union (FEDER funding). ERDF
funding (AI-Chem and INTERREG
IVa program) is gratefully ac-
knowledged for financial support
to T.T.T. A.P. thanks the Spanish
MINECO for a Ramꢄn y Cajal
contract (RYC-2009–05226) and
the European Commission for
1
2
3
4[d]
5
6
7
8
9
10
11
12
13[e]
10
50
50
50
50
50
50
50
50
50
50
50
50
100
100
100
100
80
120
100
100
100
100
100
100
100
yes
yes
yes
yes
yes
yes
yes
no
yes
no
yes
no
1.7
6.7
61.5
6.1
5.2
54
50.7
100
73
99.6
31
8.5
33
307
30
H2O
MeOH
MeOH
MeOH
26
MeOH
270
253
500
730
996
620
1032
1246
MeOH/H2O (1:1)
DMSO/H2O (1:1)
DMSO/H2O (1:1)
DMSO/H2O (1:1)
DMSO/H2O (1:1)
DMSO/H2O (1:1)
DMSO/H2O (1:1)
500
1000
1000
2000
2000
10000
51.6
12.5
no
[a] S/C=substrate (bicarbonate)/catalyst ratio; [b] bicarbonate (5 mmol), complex 5, Me3NO (0 or 1 equiv/[Fe]),
5 mL of solvent, 20 h; [c] Determined by 1H NMR analysis using DMF as an internal standard; [d] complex 7
was used; [e] Bicarbonate (25 mmol).
electron-rich cyclopentadienone framework. Its efficiency was
demonstrated in reductive amination of a broad range of car-
bonyl derivatives and amines and in hydrogenation of bicar-
a
Career Integration Grant
(CIG09-GA-2011–293900).
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Communication
[3] P. Dupau, M.-L. Tran Do, S. Gaillard, J.-L. Renaud, Angew. Chem. Int. Ed.
2014, 53, 13004.
[4] a) S. Fleischer, S. Zhou, K. Junge, M. Beller, Angew. Chem. Int. Ed. 2013,
52, 5120; Angew. Chem. 2013, 125, 5224; b) S. Zhou, S. Fleischer, K.
Junge, M. Beller, Angew. Chem. Int. Ed. 2011, 50, 5120; Angew. Chem.
2011, 123, 5226.
[5] a) A. Pagnoux-Ozherelyeva, N. Pannetier, D. M. Mbaye, S. Gaillard, J.-L.
Renaud, Angew. Chem. Int. Ed. 2012, 51, 4976; Angew. Chem. 2012, 124,
5060; b) S. Moulin, H. Dentel, A. Pagnoux-Ozherelyeva, S. Gaillard, A.
Poater, L. Cavallo, J.-F. Lohier, J.-L. Renaud, Chem. Eur. J. 2013, 19,
17881.
[6] D. S. Mꢀrel, M. Elie, J.-F. Lohier, S. Gaillard, J.-L. Renaud, ChemCatChem
2013, 5, 2939.
[7] For a recent review on Knçlker’s iron complex, see: A. Quintard, J. Ro-
driguez, Angew. Chem. Int. Ed. 2014, 53, 4044.
[8] a) H.-J. Knçlker, H. Goesmann, R. Klaus, Angew. Chem. Int. Ed. 1999, 38,
702; Angew. Chem. 1999, 111, 727; b) H.-J. Knçlker, E. Baum, H. Goes-
mann, R. Klaus, Angew. Chem. Int. Ed. 1999, 38, 2064; Angew. Chem.
1999, 111, 2196.
[9] For a review on transition metal frustrated Lewis pairs, see: S. R. Flynn,
D. F. Wass, ACS Catal. 2013, 3, 2574.
[10] a) E. Haak, Eur. J. Org. Chem. 2007, 2815; b) E. Haak, Eur. J. Org. Chem.
2008, 788.
[11] For recent reviews, see: a) F. J. Fernꢅndez-Alvarez, A. M. Aitani, L. Oro,
Catal. Sci. Technol. 2014, 4, 611; b) Y.-N. Li, R. Ma, L.-N. He, Z.-F. Diao,
Catal. Sci. Technol. 2014, 4, 1498; c) C. Maeda, Y. Myazaki, T. Ema, Catal.
Sci. Technol. 2014, 4, 1482; d) A. Tlili, E. Blondiaux, X. Frogneux, T.
Cantat, Green Chem. 2015, 17, 157.
[12] C. Federsel, A. Boddien, R. Jackstell, R. Jennerjahn, P. J. Dyson, R. Scopel-
liti, G. Laurenczy, M. Beller, Angew. Chem. Int. Ed. 2010, 49, 9777; Angew.
Chem. 2010, 122, 9971.
[13] C. Ziebart, C. Federsel, P. Anbarasan, R. Jackstell, W. Baumann, A. Span-
nenberg, M. Beller, J. Am. Chem. Soc. 2012, 134, 20701.
[14] R. Langer, Y. Diskin-Posner, G. Leitus, L. J. W. Shimon, Y. Ben-David, D.
Milstein, Angew. Chem. Int. Ed. 2011, 50, 9948; Angew. Chem. 2011, 123,
10122.
[15] F. Bertini, I. Mellone, A. Ienco, M. Peruzzini, L. Gonsalvi, ACS Catal. 2015,
5, 1254.
[16] At 1008C, the in situ generation of the 16-electron species in a mixture
of DMSO/water and base was previously reported, but direct CO re-
moval could not be ruled out. See: A. Tlili, J. Schranck, H. Neumann, M.
Beller, Chem. Eur. J. 2012, 18, 15935.
Figure 4. Transition state III–IV for 5 (a) and 7 (b). Selected distances are
given in ꢂ.
[17] All calculations were performed with the Gaussian 09 package at the
BP86 GGA level using the SDD ECP on Fe and the SVP basis set on all
main-group atoms. Including the thermal corrections at the BP86/SVP
level, the reported free energies have been obtained by means of
single-point calculations at the M06 level with the TZVP basis set on
main-group atoms, where solvent effects (EtOH) were included with
the PCM model.
Keywords: amination
hydrogenation · iron · reduction
·
homogeneous
catalysis
·
[1] a) R. H. Morris, Chem. Soc. Rev. 2009, 38, 2282; b) S. Gaillard, J.-L.
Renaud, ChemSusChem 2008, 1, 505; c) K. Junge, K. Schrçder, M. Beller,
Chem. Commun. 2011, 47, 4849; d) S. Chakraborty, H. Guan, Dalton
Trans. 2010, 39, 7427; e) M. Darwish, M. Wills, Catal. Sci. Technol. 2012,
2, 243; f) B. A. F. Le Bailly, S. P. Thomas, RSC Adv. 2011, 1, 1435; g) R. M.
Bullock, Science 2013, 342, 1054.
Received: February 20, 2015
[2] D. S. Mꢀrel, M.-L. Tran Do, S. Gaillard, P. Dupau, J.-L. Renaud, Coord.
Chem. Rev. 2015, 288, 50.
Published online on && &&, 0000
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COMMUNICATION
&
Hydrogenation
T.-T. Thai, D. S. Mꢀrel, A. Poater,*
S. Gaillard, J.-L. Renaud*
&& – &&
Highly Active Phosphine-Free
Bifunctional Iron Complex for
Hydrogenation of Bicarbonate and
Reductive Amination
Born of frustration: Based on a
hydrogenation. This complex demon-
strates high efficiencies in reductive
amination and in the reduction of
bicarbonate into formate.
“transition metal frustrated Lewis pair”
approach, a phosphine-free iron com-
plex has been prepared and applied in
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ÝÝ These are not the final page numbers!