Stabilized Ru[(H2O)6]3+ in Confined Spaces (MOFs and Zeolites) Catalyzes the Imination of Primary Alcohols under Atmospheric Conditions with Wide Scope

Article abstract of DOI:10.1021/acscatal.8b03228

Imines are ubiquitous intermediates in organic synthesis, and the metal-mediated imination of alcohols is one of the most direct and simple methods for their synthesis. However, reported protocols lack compatibility with many other functional groups since basic supports/media, pure oxygen atmospheres, and/or released hydrogen gas are required during reaction. Here we show that, in contrast to previous metal-catalyzed methods, hexa-aqueous Ru(III) catalyzes the imination of primary alcohols with very wide functional group tolerance, at slightly acid pH and under low oxygen atmospheres. The inorganic metal complex can be supported and stabilized, integrally, within either faujasite-type zeolites (Y and X) or a metal organic framework (MOF), to give a reusable heterogeneous catalyst which provides an industrially viable process well below the flammability limit of alcohols and amines.

Full text of DOI:10.1021/acscatal.8b03228

Subscriber access provided by UNIVERSITY OF TOLEDO LIBRARIES
Article
Stabilized Ru[(H2O)6]3+ in Confined Spaces (MOFs and
Zeolites) Catalyzes the Imination of Primary Alcohols
under Atmospheric Conditions with Wide Scope.
Marta Mon, Rosa Adam, Jesus Ferrando-Soria, Avelino Corma,
Donatella Armentano, Emilio Pardo, and Antonio Leyva-Perez
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.8b03228 • Publication Date (Web): 28 Sep 2018
Downloaded from http://pubs.acs.org on September 28, 2018
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a service to the research community to expedite the dissemination
of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in
full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully
peer reviewed, but should not be considered the official version of record. They are citable by the
Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore,
the “Just Accepted” Web site may not include all articles that will be published in the journal. After
a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web
site and published as an ASAP article. Note that technical editing may introduce minor changes
to the manuscript text and/or graphics which could affect content, and all legal disclaimers and
ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or
consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W.,
Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 7
ACS Catalysis
1
2
3
4
5
6
7
8
9
Stabilized Ru[(H2O)6]3+ in Confined Spaces (MOFs and Zeolites) Cata-
lyzes the Imination of Primary Alcohols under Atmospheric Condi-
tions with Wide Scope.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Marta Mon,† Rosa Adam,†† Jesús Ferrando–Soria,† Avelino Corma,*†† Donatella Armentano,*†††
Emilio Pardo*† and Antonio Leyva–Pérez.*††
†
Instituto de Ciencia Molecular (ICMOL). Universitat de València. Paterna 46980, València (Spain).
†† Instituto de Tecnología Química (UPV–CSIC). Universitat Politècnica de València–Consejo Superior de Investiga-
ciones Científicas. Avda. de los Naranjos s/n, 46022 Valencia, Spain.
††† Dipartimento di Chimica e Tecnologie Chimiche Università della Calabria. 87030, Rende, Cosenza, Italy.
ABSTRACT: Imines are ubiquitous intermediates in organic synthesis and the metal–mediated imination of alcohols is
one of the most direct and simple method for their synthesis. However, reported protocols lack compatibility with many
other functional groups since basic supports/media, pure oxygen atmospheres and/or released hydrogen gas are required
during reaction. Here we show that, in contrast to previous metal–catalyzed methods, hexa–aqueous Ru(III) catalyzes the
imination of primary alcohols with very wide functional group tolerance, at slightly acid pH and under low oxygen at-
mospheres. The inorganic metal complex can be supported and stabilized, integrally, within either a faujasite–type zeo-
lites (Y and X) or a metal organic framework (MOF), to give a reusable heterogeneous catalysts which provides an indus-
trially viable process well–below the flammability limit of alcohols and amines.
KEYWORDS: imine • ruthenium • catalysis • zeolite • metal–organic framework.
Ru is one of the most used and versatile metal catalysts
for the dehydrogenation of alcohols,1 however, it is barely
used for the dehydrogenating imination reaction.2 In one
hand, acceptorless catalytic Ru(II) complexes (i.e. pincer–
type organoRu(II) complexes)3 produce H2 during the
reaction, which reduces the imine, and in the other hand,
high–valent Ru (IV) and (VI) compounds (i.e. tetraprop-
ylammonium perruthenate, TPAP, and RuO2)4 and Ru(II)
catalysts (i.e. Ru(PPh)3Cl2 and Ru(p–cymene)Cl2)5 use
sacrificial oxidants to quench the Ru–hydrides, which are
not compatible with many functional groups.
Table 1 (entries 1–14) shows the imination of 4–
vinylbenzyl alcohol (1) and 3,4–dimethylaniline (2) cata-
lyzed by a 5 mol% of 15 representative Ru catalysts, in
toluene at 90 ºC, and with 2 equivalents of O2, which cor-
responds to the amount of air in the vial. Notice that
these atmospheric conditions are extremely mild and ful-
fill flammability limitations in industry for organic com-
pounds. The first results in Table 1 confirm the difficulties
mentioned above, and Ru(II) or (III), salts and complexes
(entries 1–5), pincer–type complexes (entries 7–10) and
supported Ru nanoparticles (entries 11–12) do not give
imine 3 (complex A Milstein´s aceptorless dehydrogenat-
ing catalyst gives 35% of the amine product, entry 6),2c
while high–valent Ru compounds (entries 13–14) act as
stoichiometric rather than catalytic agents, to yield the
amount of imine 3 corresponding to reducible Ru.
In contrast, [Ru(H2O)6]3+ (entry 15) shows truly catalytic
activity and achieves 21% of imine 3. This Ru species, pre-
pared in HBF4 solutions in the 60´s9 and later supported
in faujasite–type zeolites by simple cation exchange,10 has
rarely been reported for catalysis,11 despite its simplicity.
The combination of acidity, accessibility and water–
compatibility in a same Ru site seems favorable for the
imination of alcohols. Unfortunately, monitoring the ho-
mogeneous reaction by in–situ ultraviolet–visible (UV–
vis) spectroscopy combined with kinetic experiments
(Figure S1), with non–chromophoric reagents, showed
Indeed, it is difficult to find functional group tolerant
protocols for the imination of alcohols for any metal cata-
lyst.2a,6 The metal catalyst faces the challenge of avoiding
hydrogen borrowing mechanisms by rapidly quenching or
releasing the so–formed hydrides and, at the same time,
shifting the equilibrium towards the imine product. These
combined redox/acid–base requirements are even more
hampered for aldimines, key intermediates for the syn-
thesis of a plethora of commercially–relevant nitrogen–
containing organic molecules,7 since the dehydrogenation
of primary alcohols requires strong basic conditions and
promote decarbonylation reactions.8 Should any powerful
Ru catalyst for the dehydrogenation of alcohols operate in
non–basic media and engage amines without giving hy-
drogen atoms back nor using strong oxidizing conditions,
an inherently very active and selective metal catalyst for
the direct imination of alcohols will arise.
ACS Paragon Plus Environment

ACS Catalysis
Page 2 of 7
Table 1. Results for the imination of 4–vinylbenzyl alco-
hol (1) and 3,4–dimethylaniline (2) with Ru catalysts.
[Ru(H2O)6]3+ may preserve its integrity and catalytic activ-
ity for longer. Indeed, Ru[(H2O)6]3+–NaY (1 wt% Ru in the
zeolite, entry 20) gives a 65% of isolated imine 3, 63% in 2
gram–scale, and the solid is recyclable for at least 5 times
without significant depletion in catalytic activity (58%).
Hot–filtration experiments, at 20% conversion, show no
catalytic activity after solid catalyst filtration, and ICP
analysis confirm that the Ru loading keeps constant on
NaY after use. A NaY sample exchanged with 3 wt% in-
stead of 1 wt% Ru (see footnote in Table 1) works similar-
ly, thus saving catalytic solid material. Diffuse reflectance
(DR) UV–vis and infrared (IR) spectroscopy, together
with Ru3p X–ray photoelectron spectroscopy (XPS) of
[Ru(H2O)6]3+–NaY treated with air in the XPS chamber at
100 ºC, confirms the stability of the Ru(III) site (Figures S2
and S3).12 These results strongly support the heterogene-
ous character of the catalysis.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Entry
1
Ru catalyst
Yield of 3 (%)a
RuCl3
0
2
Ru(acac)3
0
Hydrophobic solvents (hexane, α,α,α–trifluorotoluene
and toluene) work better than polar solvents (Table S1),
plausibly by enhancing zeolite–Ru[(H2O)6]3+ ionic interac-
tion. In order to assess that this zeolite–Ru[(H2O)6]3+ in-
teraction is crucial for the catalysis, faujasite electronics
was varied by cation exchange, from electron poor (thus
highly acid, HY) to electron–rich (thus highly basic, CsX).
DR UV–vis and IR spectra of the zeolites show the ex-
pected peaks for [Ru(H2O)6]3+ and the absence of direct
oxo–Ru bonds with the zeolite walls (Figures S2 and S5),
which supports the integrity of the hexa–aqueous com-
plex. The catalytic activity of the different [Ru(H2O)6]3+–
zeolite catalysts changes with the electronics, peaking for
NaY and KY (Figure S4).13 The fact that the quasi neutral
faujasite KY confers the better catalytic activity to the
extraframework Ru(III) site discards the participation of
zeolite Brönsted sites during the imination reaction14 and
strongly supports [Ru(H2O)6]3+ as the intrinsic catalyst,
stabilized in the zeolite. Following this hypothesis, it
seemed highly promising to prepare new active solid cata-
lysts by supporting [Ru(H2O)6]3+ in other delocalized ani-
onic solids, such as MOFs.
3
RuCl2(PPh)3
0
4
RuCl2(NH3)6
0
5
RuCl2(p–cymene)
Complex A
0
6b
7
0
Complex B
0
8
Complex C
5
9
Complex D
0
10
11
12
13
14
15
16
17
18
19
20c
21d
22
Complex E
0
Ru (5 wt%)–C
0
Ru–Al2O3
0
TPAP
36
RuO2
14
Ru[(H2O)6]·3BF4
Ru(H2O)6–Al2O3 (0.1 wt% Ru)
Ru(H2O)6–SiO2 (0.1 wt% Ru)
Ru(H2O)6–TiO2 (0.1 wt% Ru)
Ru(H2O)6–MgO (0.1 wt% Ru)
Ru[(H2O)6]3+–NaY (1 wt% Ru)
[RuH2O)6]3+–MOF (~3 wt% Ru)
Ru(OH)3– Al2O3 (1 wt% Ru)
21 (18)
27
26
23
20
73 (65)
97 (90)
7
MOFs15 are porous crystalline materials showing a large
variety of interesting properties –most of which arise from
their porous character and amazing host–guest chemis-
try16– and find application in many different important
fields.15b In particular, MOFs have already shown excellent
results in supporting and stabilizing small metal clusters17
or metal complexes18 within their channels, showing high
catalytic activity.19 In this context, we thus selected a
a
2 equivalents of O2 corresponds to the air in the vial. GC yields. Between
b
c
parentheses, isolated yields. Hydrogenated imine as only product found.
63% isolated yield in 2 gram–scale; 58% after 5 uses. A 3 wt% sample gives
56% isolated yield. d Bare zeolites and MOF do not give any product.
the rapid degradation and the loss of catalytic activity of
[Ru(H2O)6]3+ in toluene solution.
A plausible way to overcome such a catalyst degrada-
tion in solution is to support the Ru active species onto a
solid. However, this degradation is not avoided when
supporting [Ru(H2O)6]3+ on different amorphous inorgan-
ic oxides such as alumina, silica, titania and magnesia
(entries 16–19), since the progressive loss of the fragile
hexa–aqueous Ru(III) cation still occurs.
highly
robust
anionic
MOF
of
formula
Ni2II{NiII [CuII (Me3mpba)2]3} · 54H2O, capable to ex-
4
2
change the Ni2+ cations hosted within its pores by
[Ru(H2O)6]3+, in a similar procedure to cation exchange in
zeolites. The post–synthetic20 single crystal to single crys-
tal (SC to SC) process21 was monitored through SEM–EDX
and ICP–AES (Table S2), whereas Ru oxidation state and
oxygen atom electronics were determined by X–ray pho-
toelectron spectroscopy (XPS, Figures S6–S7). Figure 1
shows the single crystal X–ray crystallography (SC–XRC)
[Ru(H2O)6]3+ depletion may come from the loss of ionic
interaction in the organic medium between the soft
-
Ru(III) cation and the BF4 /inorganic oxide counterbal-
ancing anion, and, perhaps, a confining anionic solid with
a delocalized charge and an intimate interaction with
results
for
the
new
MOF,
with
formula
ACS Paragon Plus Environment

Page 3 of 7
ACS Catalysis
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 1. Views of the porous crystal structures, determined by single crystal X–ray diffraction, of [Ru(H2O)6]3+–MOF in the ab
(a) and bc (b) planes, respectively. (c) Perspective view one single channel of [Ru(H2O)6]3+–MOF along the c (left) axis. d) Per-
spective view of a fragment of a single channel emphasizing the hydrogen bonds interactions. Cu(II) and Ni(II) cations from the
coordination network are represented by cyan and blue polyhedra, respectively, whereas the ligands are depicted as gray sticks.
Ru(III) cations and water molecules hosted in the channels are represented by gold and red spheres with surface, respectively.
[RuIII(H2O)6]0.83[RuIII2(µ–
vastly solvated confined nanospace
̶
in which water mole-
is at the origin of
H2O)(H2O)10]0.25{NiII [CuII (Me3mpba)2]3}
·
61H2O
cules are noninnocent participants
̶
4
2
[Ru(H2O)6]3+ moieties stabilizations and unambiguously
confirm the integrity of [Ru(H2O)6]3+ within the porous
solid.
([Ru(H2O)6]3+–MOF).
Figure 1a shows the [Ru(H2O)6]3+ and [RuIII2(µ–
H2O)(H2O)10]6+ units, respectively hosted in the two types
of channels present in the anionic framework: the larger
octagonal ones much more accessible for catalysis (vide
infra) and the small square hindered channels. Both the
hexa–aqua Ru(III) monomers, located in octagonal pores
and [RuIII2(µ–H2O)(H2O)10]6+ dimers, exhibit Ru–OH2
bond distances [1.97(1) to 2.37(3) Å], very similar to the
only one report found in the literature.22 This lack of
reports on crystallographically defined [Ru(H2O)6]3+
monomers further supports an intrinsic stabilizing effect
of MOF’s confined space. The larger octagonal
hydrophilic channels of the MOF, contain a much larger
accessible void space (size of ca. 2.2 nm), which contrasts
with the very small amount of room available in the small
square channels, almost fully occupied by the [RuIII2(µ–
H2O)(H2O)10]6+ dimers (Figure 1c and 1d). This point
suggests that the [Ru(H2O)6]3+ monomers located in the
larger channels are potential catalytic species. Apart from
electrostatic interactions between Ru3+ units and the
anionic framework, all [Ru(H2O)6]3+ cations located in
both types of channels are hydrogen–bonded – involving
the carboxylate oxygen atoms of the framework and water
molecules constituting the coordination environment of
the Ru3+ ions [Owaters···Ooxamate 2.827(3) and 2.923(3) Å] to
the anionic framework, which further fixes and stabilizes
them within the pores (dashed lines in Figures 1c, 1d and
S8–S10). These results definitely underline how the inter-
play between hydrophilic channels and the consequent
The experimental powder X–ray diffraction (PXRD)
patterns of a polycrystalline sample of [Ru(H2O)6]3+–MOF
is identical to the theoretical one (Figure S11), which con-
firms the purity of the bulk. Moreover, the chemical na-
ture was further determined by elemental analysis (Sup-
porting Information) and the water contents was estab-
lished by thermogravimetric analysis (TGA, Figure S12).
There is a continuously loss of mass before 150 °C, howev-
er, this corresponds to physisorbed water an organic sol-
vent traces, and not to the aqueous complex, that decom-
poses at much higher temperature. Finally, the porosity of
the MOF after the PS cation exchanged was confirmed by
measuring the N2 adsorption isotherm at 77 K (Figure
S13).
The [Ru(H2O)6]3+–MOF catalyst gives 90% isolated yield
of imine 3 (entry 21 in Table 1), the highest among all Ru
catalysts tested. Hot–filtration experiments and ICP anal-
ysis show that Ru remains on the MOF after reaction, and
XPS confirms the stability of the Ru catalyst within the
MOF (Figures S6–S7). Kinetic experiments show that the
initial
turnover
frequency
TOF0
for
soluble
Ru[(H2O)6]3+·3BF4 , Ru[(H2O)]63+–NaY and Ru[(H2O)63+]–
MOF is similar, measured at initial reaction times when
degradation is still no significant (Figure S14), and that
product formation increases longer for the MOF catalyst.
These results confirm that the catalytic activity is intrinsic
-
ACS Paragon Plus Environment

ACS Catalysis
Page 4 of 7
1
2
3
4
5
6
7
8
3+-solid
]
[Ru(H2O)6]3+–NaY stored for 15 years in the bench shows
O)6
Ru[(H2
H
(5 mol%)
R2-NH2
R2
the same catalytic activity than a fresh sample, and the
same occurs for [Ru(H2O)6]3+–MOF stored for 1 year. These
results illustrate the robustness of the supported
[Ru(H2O)6]3+ catalysts. Notice that flammability limits in
industry for organic compounds generally restrict O2
concentration below 20%, thus the results here presented
are not only of interest for imine synthesis in the
+
+
2 H
2O
R1 OH
(1 equiv.)
R1
N
Toluene (0.5 M),
1= aryl, vinyl,
2, 2 equiv),
2= aryl, alkyl.
closed vial (O
R
R
4-33
reflux, 18 h
cynnamyl.
Me
N
Me
Me
Me
Me
R3
3-Br
Me
R4
4
, 62%
14
Cl
, 96%
5
3-CN
, 73%
, 93%
, 92%
9
N
15
Ph
, 97%
4-Br 6
N
laboratory but also for
production.
a plausible industrial scale
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
7
4-H
N
Me
4-NO2
4-SMe
8
, 98%
S
N
9
, 92%
R3
The imination reaction shown in Table 1 does not pro-
ceed in complete absence of O2, and H2 is not detected in
the reaction atmosphere, even at [O2] << air. If 1–dodecene
and Pd/C (5 wt%) are added from the beginning to a reac-
tion under optimized conditions (>80% of 3), no alkene
hydrogenation occurs. These results discard acceptorless
mechanisms and support a very efficient Ru–hydride
quenching by O2 during reaction. The corresponding ki-
netic equation, according to kinetic results at initial times,
is v0=kapp[1][O2][Ru] at [O2]<air, and simply v0=k´app[1][Ru]
at higher [O2] (Figure S15), which reflects a rapid satura-
tion of the catalytic site for [O2]>air and that amine 2 does
not participate in the rate–determining step (r.d.s.) of the
reaction. In accordance, the dehydrogenation initial rate of
1, without adding amine 2, is very similar to the imination
initial rate when 2 is present, and a kinetic isotopic effect
(KIE)= 2.8 is obtained when α,α–deuterated benzyl alcohol
(PhCD2OH) is used, regardless if amine 2 is present or not.
These results strongly support that alcohol dehydrogena-
tion is the rate–limiting step of the imination, and that
amine condensation and Ru–hydride capture by O2, to
form water, are much faster processes.
A possible general mechanism for the Ru[(H2O)6]3+ imina-
tion reaction, either supported or not, is shown in Figure 3.
Notice that the confining solids maximize the synthesis
and lifetime of the Ru[(H2O)6]3+ species, but do not have a
direct role in the reaction mechanism. The bigger pore size
of the MOF respect to the zeolite can explain the better
catalytic activity of the former (>20% yield increase for
product 3), however, the porosity of both solids is enough
for reactants/products diffusion and does not hamper the
reaction outcome.
R4
10
, 98%
4-COOMe
13
, 59%
12
, 53%
4-CF3
11
, 91%
O
S
N
O
R8
R6
R7
n
(CH2)
N
N
N
N
N
OH
R6
HO
R6
NO2
22
F
F
, 60%
R9
R5
, R9
R8
, R7
R6
R6
H,
R5
,
n
23
, 78%
Me, NO2
20
18
, 79%
19
, 46%
16
, 88%
Cl
H, CH=CH2
0
24
OMe, CH=CH2
, 82%
21
CF
3, CF3 , 86%
17
OMe, 4
, 90%
SMe
, 48%
Me
Me
O
O
B
O
N
N
N
N
R10
Me
N
R11
N
N
R11
R10
26
, 91%
Cl
31
, 60%
29
H
, 52%
27
H
, 46%
25
, 64%
Me 30
, 52%
28
Me
, 64%
Cl
Me
R12
R12
Me
Me
Me
Me 32
nPr
, 44%
33
, 40%
N
N
R12
Figure 2. Scope for the imination of primary alcohols with
amines using either Ru[(H2O)6]3+–NaY, –KY or –MOF as a
catalyst. Imines 6, 7 and 9–10 were catalyzed by the MOF;
imines 11–13 by KY, and the rest by NaY. The same yield of
imine 4 is obtained with a 15–year old NaY catalyst, and the
same occurs with imine 6 and the MOF. 2 equivalents of
O2 corresponds to the air in the vial.
to [Ru(H2O)6]3 and that keeps for longer on solids that
The proposed mechanism involves that the alcohol dis-
stabilize better the catalyst. Notice that a related catalyst, places one water ligand on Ru3+ to trigger a beta–hydrogen
Ru(OH)3–Al2O3, prepared in highly alkaline solutions and
elimination, and that the intermediate Ru–H species is
rapidly quenched by O2. The so–formed aldehyde conden-
very active for dehydrogenations of alcohols,23 is merely
inactive here since amine condensation is hampered under sates with the amine under acid catalysis to give the final
strong basic conditions.
imine product.
Figure 2 shows that Ru[(H2O)6]3+–NaY, –KY and –MOF
catalyze the imination of primary benzyl and allyl alcohols
with different amines in good isolated yields and selectivi-
ty under aerobic conditions, tolerating halogen (imines 4,
6, 14, 16, 20–21, 25–26), cyano (5), alkene (7, 16–17, 20 and
24), nitro (8 and 22–23), thioether (9 and 17), ester (10),
trifluoromethane (11 and 21), heteroaromatic (12–13 and
31), alkyne (14–15), phenol (18–19), ether (19, 24 and 26),
sulfonamide (22), boronic ester (25) and enamine (27–30)
functionalities in the molecule. For alkyl enamines, cy-
clization occurs to give the corresponding Doebner–Miller
quinoline products 32–33, which reflects the acidity im-
H
H
HO
R1
2H
2O
Ru3+
O)6
(H2
3O+
H
1/2 O2
3O+
+ H
Beta-hydrogen
elimination
H
O
H
Hydride
quenching
Ru3+
R1
O)5
Ru3+
(r.d.s.)
H
H
O
O)5
(H2
(H2
R2-NH2
or H
H
Amine
R2
N
R1
condensation
3O+
R1
Ru3+
catalyst
Figure 3. Mechanism of the [Ru(H2O)6]3+–catalyzed
imination of primary alcohols with amines.
parted by the Ru3+ aqueous cation.
A sample of
ACS Paragon Plus Environment

Page 5 of 7
ACS Catalysis
1
2
3
4
5
6
7
8
9
Milstein, D. Direct synthesis of imines from alcohols and amines
with liberation of H2. Angew. Chem. Int. Ed. 2010, 49, 1468–1471. d)
Cano, R.; Ramon, D. J.; Yus, M. Impregnated Ruthenium on Mag-
netite as a Recyclable Catalyst for the N-Alkylation of Amines,
Sulfonamides, Sulfinamides, and Nitroarenes Using Alcohols as
Electrophiles by a Hydrogen Autotransfer Process. J. Org. Chem.
2011, 76, 5547−5557. e) Saha, B.; Wahidur Rahaman, S. M.; Daw,
P.; Sengupta, G.; Bera, J. K. Metal–Ligand Cooperation on a Diru-
thenium Platform: Selective Imine Formation through Acceptor-
less Dehydrogenative Coupling of Alcohols with Amines. Chem.
Eur. J. 2014, 20, 6542–6551. f) Oldenhuis, N. J.; Dong, V. M.; Guan,
Z. Catalytic acceptorless dehydrogenations: Ru-Macho catalyzed
construction of amides and imines. Tetrahedron 2014, 70, 4213–
4218. g) Higuchi, T.; Tagawa, R.; Iimuro, A.; Akiyama, S.; Nagae,
H.; Mashima, K. Tunable Ligand Effects on Ruthenium Catalyst
Activity for Selectively Preparing Imines or Amides by Dehydro-
genative Coupling Reactions of Alcohols and Amines. Chem. Eur.
J. 2017, 23, 12795–12804.
(3) a) Gunanathan, C.; Milstein, D. Metal–Ligand Cooperation
by Aromatization–Dearomatization: A New Paradigm in Bond
Activation and “Green” Catalysis Acc. Chem. Res. 2011, 44, 588–
602. b) Gunanathan, C.; Milstein, Applications of Acceptorless
Dehydrogenation and Related Transformations in Chemical Syn-
thesis. Science 2013, 341, 1229712. c) Crabtree, R. H. Homogeneous
Transition Metal Catalysis of Acceptorless Dehydrogenative Alco-
hol Oxidation: Applications in Hydrogen Storage and to Hetero-
cycle Synthesis. Chem. Rev. 2017, 117, 9228−9246.
In summary, the imination of primary alcohols catalyzed
by [Ru(H2O)6]3+ supported on structured porous solids
occurs in high yields and with a wide functional group
tolerance under aerobic conditions, which is a step
forward for imine synthesis. This work constitutes an
example of cross–fertilization between zeolites and MOFs
to support catallytically active metal species.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ASSOCIATED CONTENT
Supporting Information. CCDC–1841425 contains the sup-
plementary crystallographic data for this paper. These data
are provided free of charge by The Cambridge Crystallograph-
ic Data Centre.
Additional experimental procedures, X–ray crystallographic
data collection, Figures, Tables and compound characteriza-
tion. This material is available free of charge via the Internet
at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
* To whom correspondence should be addressed. E–mails:
anleyva@upv.itq.es; emilio.pardo@uv.es; donatel-
la.armentano@unical.it; acorma@upv.itq.es.
Notes
(4) a) Ley, S. V.; Norman, J.; Griffith, W. P.; Marsden, S. P.
Tetrapropylammonium Perruthenate, Pr4N+RuO4-, TPAP:
A
The authors declare no competing financial interests.
Catalytic Oxidant for Organic Synthesis. Synthesis 1994, 7, 639–
666. b) Lenz, R.; Ley, S. V. Tetra-n-propylammonium perruthe-
nate (TPAP)-catalysed oxidations of alcohols using molecular
oxygen as a co-oxidant. J. Chem. Soc., Perkin Trans. 1997, 1, 3291–
3292. c) Over, H. Surface Chemistry of Ruthenium Dioxide in
Heterogeneous Catalysis and Electrocatalysis: From Fundamental
to Applied Research. Chem. Rev. 2012, 112, 3356–3342.
(5) a) Zhang, S.–Y.; Tu, Y.–Q.; Fan, C.–A.; Jiang, Y.–J.; Shi, L.;
Cao, K.; Zhang, E. Cross-Coupling Reaction between Alcohols
through sp3 C-H Activation Catalyzed by a Ruthenium/Lewis Acid
System. Chem. Eur. J. 2008, 14, 10201–10205.
(6) a) Tian, H.; Yu, X.; Li, Q.; Wang, J.; Xua, Q. General, Green,
and Scalable Synthesis of Imines from Alcohols and Amines by a
Mild and Efficient Copper-Catalyzed Aerobic Oxidative Reaction
in Open Air at Room Temperature. Adv. Synth. Catal. 2012, 354,
2671–2677. b) Zhang, G.; Hanson, S. K. Cobalt-catalyzed acceptor-
less alcohol dehydrogenation: synthesis of imines from alcohols
and amines. Org. Lett. 2013, 15, 650−653. c) Bain, J.; Cho, P.;
Voutchkova–Kostal, A. Recyclable hydrotalcite catalysts for alco-
hol imination via acceptorless dehydrogenation. Green Chem.
2015, 17, 2271–2280. d) Mukherjee, A.; Nerush, A.; Leitus, G.;
Shimon, L. J. W.; Ben David, Y.; Espinosa Jalapa, N. A.; Milstein,
D. Manganese-Catalyzed Environmentally Benign Dehydrogena-
tive Coupling of Alcohols and Amines to Form Aldimines and H2:
A Catalytic and Mechanistic Stud. J. Am. Chem. Soc. 2016, 138,
4298−4301. e) Jaiswal, G.; Landge, V. G.; Jagadeesan, D.; Balara-
man, E. Sustainable iron-catalyzed direct imine formation by
acceptorless dehydrogenative coupling of alcohols with amines.
Green Chem. 2016, 18, 3232–3238.
(7) a) Pruett, R. L.; Keenan, M. J.; Mozeleski, E. J. US patent
US 5103058, 1992, 8 pp., Exxon Chemical Patents, Inc. USA. b)
Martin, S. F. Recent applications of imines as key intermediates in
the synthesis of alkaloids and novel nitrogen heterocycles. Pure
Appl. Chem. 2009, 81, 195–204.
(8) a) Cho, C. S.; Kim, B. T.; Kim, H.–S.; Kim, T.–J.; Shim, S. C.
Ruthenium-Catalyzed One-Pot β-Alkylation of Secondary Alco-
hols with Primary Alcohols. Organometallics 2003, 22, 3608–3610.
b) Fujita, K.; Yoshida, T.; Imori, Y.; Yamaguchi, R. Dehydrogena-
tive Oxidation of Primary and Secondary Alcohols Catalyzed by a
Cp*Ir Complex Having a Functional C,N-Chelate Ligand. Org.
Lett. 2011, 13, 2278−2281. c) Sik Cho, C.; Tae Kim, B.; Kim, T.–J.;
Author Contributions
The manuscript was written through contributions of all au-
thors. All authors have given approval to the final version of
the manuscript.
ACKNOWLEDGMENT
This work was supported by the MINECO (Spain) (Projects
CTQ2017-86735-P,
CTQ2016–75671–P,
CTQ2014–56312–P,
CTQ2014–55178–R, MAT2013–40823–R and Excellence Units
“Severo Ochoa” SEV2016–0683 and “Maria de Maeztu” and
MDM–2015–0538) and European Union through ERC–AdG–
2014–671093 (SynCatMatch) and the Ministero dell’Istruzione,
dell’Università e della Ricerca (Italy) (FFABR 2017). M. M.
thanks the MINECO for a predoctoral contract. R. A. thanks
UPV for a post–doctoral contract. J. F. –S. acknowledges
financial support from the Subprograma Atracció de Talent –
Contractes Postdoctorals de la Universitat de Valencia. We
also acknowledge SOLEIL for provision of synchrotron radia-
tion facility and thank Dr. Pierre Fertey for his assistance
REFERENCES
(1) For reviews see a) Guillena, G.; Ramón, D. J.; Yus, M. Hydro-
gen Autotransfer in the N-Alkylation of Amines and Related
Compounds using Alcohols and Amines as Electrophiles. Chem.
Rev. 2009, 110, 1611–1641. b) Sordakis, K.; Tang, C.; Vogt, L. K.;
Junge, H.; Dyson, P. J.; Beller, M.; Laurenczy, G. Homogeneous
Catalysis for Sustainable Hydrogen Storage in Formic Acid and
Alcohols. Chem. Rev. 2018, 118, 372−433. c) Corma, A.; Navas, J.;
Sabater, M. J. Advances in One-Pot Synthesis through Borrowing
Hydrogen Catalysis. Chem. Rev. 2018, 118, 1410−1459.
(2) For a review see a) Chen, B.; Wang, L.; Gao, S. Recent Ad-
vances in Aerobic Oxidation of Alcohols and Amines to Imines.
ACS Catal. 2015, 5, 5851−5876. For representative examples see b)
Jung Won, K.; Jinling, H.; Kazuya, Y.; Noritaka, M. Heterogene-
ously Catalyzed One-pot Synthesis of Aldimines from Primary
Alcohols and Amines by Supported Ruthenium Hydroxides.
Chem. Lett. 2009, 38, 920−921. c) Gnanaprakasam, B.; Zhang, J.;
ACS Paragon Plus Environment

ACS Catalysis
Page 6 of 7
1
2
3
4
5
6
7
8
Chul Shim, S. An Unusual Type of Ruthenium-Catalyzed Transfer
(20) Cohen, S. M. The Postsynthetic Renaissance in Porous Sol-
ids. J. Am. Chem. Soc. 2017, 139, 2855–2863.
(21) a) Grancha, T.; Ferrando–Soria, J.; Zhou, H.–C.; Gascon, J.;
Seoane, B.; Pasán, J.; Fabelo, O.; Julve, M.; Pardo, E. Postsynthetic
Improvement of the Physical Properties in a Metal–Organic
Framework through a Single Crystal to Single Crystal Transmetal-
lation. Angew. Chem. Int. Ed. 2015, 54, 6521–6525.
Hydrogenation of Ketones with Alcohols Accompanied by C−C
Coupling. J. Org. Chem. 2001, 66, 9020–9022. d) Mazziotta, A.;
Madsen, R. Ruthenium-Catalyzed Dehydrogenative Decarbonyla-
tion of Primary Alcohols. Eur. J. Org. Chem. 2017, 5417–5420.
(9) Merceras, E. E.; Buckley, R. Hexaaquoruthenium(II). Inorg.
Chem. 1965, 4, 1692–1695.
(10) Wan, B.–Z.; Lunsford, J. H. An EPR study of ruthenium(III)
aquo complexes in water and in zeolite-Y. Inorg. Chim. Acta Lett.
1982, 65, L29–L30.
(11) Cürdaneli, P. E.; Özkar, S. Ruthenium(III) ion-exchanged
zeolite Y as highly active and reusable catalyst in decomposition
of nitrous oxide to sole nitrogen and oxygen. Micropor. Mesopor.
Mater. 2014, 196, 51–58.
(12) a) Liang, H.; Chen, G.; Desinan, S.; Rosei, R.; Rosei, F.; Ma,
D. In situ facile synthesis of ruthenium nanocluster catalyst sup-
ported on carbon black for hydrogen generation from the hydrol-
ysis of ammonia-borane. Inter. J. Hydrogen Energy 2012, 37, 17921–
17927. b) Maximov, A.; Zolotukhina, A.; Murzin, V.; Karakhanov,
E.; Rosenberg, E. Ruthenium Nanoparticles Stabilized in Cross-
Linked Dendrimer Matrices: Hydrogenation of Phenols in Aque-
ous Media. ChemCatChem 2015, 7, 1197–1210.
(13) a) Corma, A.; García, H.; Leyva, A. Controlling the soft-
ness–hardness of Pd by strong metal–zeolite interaction: cyclisa-
tion of diallylmalonate as a test reaction. J. Catal. 2004, 225, 350–
358. b) Rubio–Marqués, P.; Rivero–Crespo, M. A.; Leyva–Pérez, A.;
Corma, A. Well-Defined Noble Metal Single Sites in Zeolites as an
Alternative to Catalysis by Insoluble Metal Salts. J. Am. Chem. Soc.
2015, 137, 11832−11837.
(14) Cabrero–Antonino, J. R.; Leyva–Pérez, A.; Corma, A. Be-
yond acid strength in zeolites: soft framework counteranions for
stabilization of carbocations on zeolites and its implication in
organic synthesis. Angew. Chem. Int. Ed. 2015, 54, 5658–5661.
(15) a) Zhou, H.–C.; Kitagawa, S. Metal–Organic Frameworks
(MOFs). Chem. Soc. Rev. 2014, 43, 5415–5418. b) Furukawa, H.;
Cordova, K. E.; O’Keeffe, M.; Yaghi, O. M. The Chemistry and
Applications of Metal-Organic Frameworks Science 2013, 341,
1230444. d) Farha, O. K.; Hupp, J. T. Rational Design, Synthesis,
Purification, and Activation of Metal−Organic Framework Mate-
rials. Acc. Chem. Res. 2010, 43, 1166–1175. d) Long, J. R.; Yaghi, O.
M. The pervasive chemistry of metal–organic frameworks. Chem.
Soc. Rev. 2009, 38, 1213–4. e) Maurin, G.; Serre, C.; Cooper, A.;
Férey, G. The new age of MOFs and of their porous-related solids.
Chem. Soc. Rev. 2017, 46, 3104–3107.
(22) Bernhard, P.; Buergi, H. B.; Hauser, J.; Lehmann, H.; Ludi,
A. Syntheses and crystal and molecular structures of
9
hexaaquaruthenium(II)
hexaaquaruthenium(III)
p-toluenesulfonate
and
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
p-toluenesulfonate,
[Ru(H2O)6](C7H7SO3)2 and [Ru(H2O)6](C7H7SO3)3.3H2O. Inorg.
Chem. 1982, 21, 3936–3941.
(23) a) Yamaguchi, K.; Mizuno, N. Supported ruthenium cata-
lyst for the heterogeneous oxidation of alcohols with molecular
oxygen. Angew. Chem. Int. Ed. 2002, 41, 4538–4542. b) Yamaguchi,
K.; Mizuno, N. Development of Highly Active Heterogeneous
Oxidation Catalysts Based on the Properties of Metal Hydroxides.
Top. Catal. 2014, 57, 1196–1207. c) Kim, Y.; Ahn, S.; Hwang, J. Y.;
Ko, D.–H.; Kwon, K.–Y. Dehydrogenative Oxidation of Alcohols
Catalyzed by Highly Dispersed Ruthenium Incorporated Titanium
Oxide. Catalysts 2017, 7, 7–18.
(16) Kitagawa, S.; Matsuda, R. Chemistry of coordination space
of porous coordination polymers. Coord. Chem. Rev. 2007, 251,
2490–2509.
(17) a) Mon, M.; Rivero–Crespo, M. A.; Ferrando–Soria, J.; Vi-
dal–Moya, A.; Boronat, M.; Leyva–Pérez, A.; Corma, A.; Hernan-
dez–Garrido, J. C.; López–Haro, M.; Calvino, J. J.; Ragazzon, G.;
Credi, A.; Armentano, D.; Pardo, E. Synthesis of Densely Pack-
aged, Ultrasmall Pt0 Clusters within a Thioether-Functionalized
2
MOF: Catalytic Activity in Industrial Reactions at Low Tempera-
ture. Angew. Chem. Int. Ed. 2018, 57, 6186 –6191.
(18) a) Fortea–Pérez, F. R.; Mon, M.; Ferrando–Soria, J.; Boro-
nat, M.; Leyva–Pérez, A.; Corma, A.; Herrera, J. M.; Osadchii, D.;
Gascon, J.; Armentano, D., Pardo, E. The MOF-driven synthesis of
supported palladium clusters with catalytic activity for carbene-
mediated chemistry. Nat. Mater. 2017, 16, 760–766. b) Mon, M.;
Ferrando–Soria, J.; Verdaguer, M.; Train, C.; Paillard, C.; Dkhil, B.;
Versace, C.; Bruno, R.; Armentano, D.; Pardo, E. Postsynthetic
Approach for the Rational Design of Chiral Ferroelectric Metal–
Organic Frameworks. J. Am. Chem. Soc. 2017, 139, 8098–8101. c)
Liu, H.; Chang, L.; Bai, C.; Chen, L.; Luque, R.; Li, Y. Controllable
Encapsulation of “Clean” Metal Clusters within MOFs through
Kinetic Modulation: Towards Advanced Heterogeneous
Nanocatalysts. Angew. Chemie Int. Ed. 2016, 55, 5019–5023.
(19) Gascon, J.; Corma, A.; Kapteijn, F.; Llabrés i Xamena, F. X.
Metal Organic Framework Catalysis: Quo vadis? ACS Catal. 2014,
4, 361–378.
ACS Paragon Plus Environment

Page 7 of 7
ACS Catalysis
1
2
3
Table of Content graphics
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ACS Paragon Plus Environment