Phosphonium-stibonium and bis-stibonium cations as pnictogen-bonding catalysts for the transfer hydrogenation of quinolines

Article abstract of DOI:10.1039/c9dt01357a

Bifunctional Lewis acidic group 15 compounds have emerged as appealing platforms for anion sensing and organocatalysis. As part of our interest in the chemistry of these compounds, we have now compared the catalytic properties of [o-(MePPh₂)C

Full text of DOI:10.1039/c9dt01357a

View Article Online
View Journal
Dalton
Transactions
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: M. Yang, M. Hirai
and F. P. Gabbaï, Dalton Trans., 2019, DOI: 10.1039/C9DT01357A.
This is an Accepted Manuscript, which has been through the
Volume 45 Number
1 7 January 2016 Pages 1–398
Royal Society of Chemistry peer review process and has been
accepted for publication.
Dalton
Transactions
Accepted Manuscripts are published online shortly after
An international journal of inorganic chemistry
www.rsc.org/dalton
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1477-9226
PAPER
Joseph T. Hupp, Omar K. Farha et al.
Efficient extraction of sulfate from water using
framework
a Zr-metal–organic
rsc.li/dalton

Please do not adjust margins
Page 1 of 5
Dalton Transactions
View Article Online
DOI: 10.1039/C9DT01357A
Journal Name
ARTICLE
Phosphonium-stibonium and bis-stibonium cations as pnictogen-
bonding catalysts for the transfer hydrogenation of quinolines
Received 00th January 20xx,
Accepted 00th January 20xx
Mengxi Yang, Masato Hirai, and François P. Gabbaï*
DOI: 10.1039/x0xx00000x
Abstract: Bifunctional Lewis acidic group 15 compounds have emerged as appealing platforms for anion sensing and
organocatalysis. As part of our interest in the chemistry of these compounds, we have now compared the catalytic
properties of [o-(MePPh2)C6H4SbPh2]+ ([3]+), [o-(PPh2)C6H4SbPh3]+ ([4]+), [o-(MePPh2)C6H4SbPh3]2+ ([5]2+), and [o-
C6H4(SbMePh2)2]2+ ([6]2+) using the transfer hydrogenation of 2-phenyl-quinoline and 3-bromoquinoline with Hantzsch
ester as a benchmark reaction. This study, which also involved an evaluation of the catalytic properties of [Ph4Sb]+ and
[Ph3MeP]+, shows that antimony cations are generally more active than their phosphorus counterparts. Our results also
demonstrate that dicationic systems such as [6]2+ are superior activators.
www.rsc.org/
Antimony halides display elevated Lewis acidity1 and have with these highly electron-deficient stibonium cations is
been used for numerous applications2 including the generation complicated by their instability toward moisture and their
of superacids.3 Organoantimony derivatives, although propensity to undergo reduction. For these reasons, we have
significantly less acidic than their halide counterparts, are now contemplated an alternative approach in which the Lewis
generally air and water stable and thus easy to handle.4-11 acidity or pnictogen-bond donor properties of the stibonium
Owing to these advantageous characteristics, organoantimony center would be enhanced by a nearby secondary cationic
derivatives have been studied as catalysts for a number of moiety.
12, 13
reactions that proceed by electrophilic pathways.2,
As
Ph
documented in recent contributions, stibines and stiboranes
featuring electron-withdrawing ligands as in the case of A and
B (Figure 1) are sufficiently Lewis acidic, or sufficiently potent
pnictogen bond donors, to promote a range of reactions
including the transfer hydrogenation of imines using Hantzsch
ester.14, 15 Because Coulombic effects may enhance the affinity
of antimony(V) centres for polar or charged substrates,
stibonium cations such as 9-anthryltriphenylstibonium (C) have
also been considered as antimony-based Lewis acids.16 Such
species, which have found applications in small anion sensing
including in water,17, 18 are also emerging as appealing catalytic
platforms for organic reaction that involve an electrophilic
activation step.19-28 Efforts to increase the Lewis acidic
properties of such cations have led us to consider stibonium
cations such as D and E where the electron-withdrawing
nature of the fluorinated aryl or halogen ligand notably
increases the electron deficiency of the antimony center.28 The
elevated Lewis acidic properties of these cations become
Cl
Cl
Cl
Ph
Ph
C6F5
C6F5
O
Sb
C6F5
C6F5
Sb
Sb
O
Cl
C6F5
C6F5
A
B
C
This work
R
R
C6F5
Ph
Sb
Ph
Ph
C6F5
C6F5
R
Sb
Sb
Cl
E
C6F5
D
Figure 1. Example of stibonium cations used as Lewis acid catalysts and general
structure of the dication targeted in this study.
To explore this idea, we targeted the phosphonium and
stibonium cations depicted in Figure 2. These cations were
synthesized as the tetrafluoroborate salts using literature
protocols in the case of [1]+,29 [2]+,30 and [6]2+,26 or by
phosphinostibine
C6H4(PPh2)(SbPh2) with MeI followed by I-/BF4 anion exchange
methylation
of
the
known
o-
manifest in their ability to catalyse the dimerization of 1,1-
-
28
diphenylethylene or the polymerization of THF.27,
While
in the case of [3][BF4] (Scheme 1). Salt [4][BF4] was obtained by
reaction of o-(Ph2P)C6H4Li with Ph3SbBr2 followed by Br-/BF4
these elevated Lewis acidic properties are attractive, working
-
anion exchange (Scheme 1). Salt [4][BF4] could be converted
into [5][BF4]2 using trimethyloxonium tetrafluoroborate
(Scheme 1). All salts obtained can be stored in air for extended
periods of time. The stability of [5]2+ is particularly surprising if
one considers that [o-C6H4(PPh2Me)2]2+ undergoes rapid
Department of Chemistry, Texas A&M University, College Station, TX 77843, USA
Email: francois@tamu.edu.
Electronic Supplementary Information (ESI) available: Experimental details,
crystallographic data of ## in cif format. NMR spectra, and additional ##. See
DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 2 of 5
ARTICLE
Journal Name
View Article Online
DOI: 10.1039/C9DT01357A
Figure 3. Crystal structure of a) [3][BF4], b) [4][BF4] and c) [5][BF4]2. Thermal ellipsoids ae drawn at the 50 % probability level. The hydrogen atoms and the free [BF4]-
anions are omitted for clarity. Selected bond lengths (Å) and angles (deg) for [1][BF4]: Sb1-P1 = 3.540(2), C1-Sb1-C7 = 96.1(2), C1-Sb1-C13 = 96.7(2), C7-Sb1-C13 =
98.5(2), C2-P1-C31 = 112.3(3), C2-P1-C19 = 107.6(3), C2-P1-C25 = 109.8(3), Sb1-C1-C2 = 122.7(4), P1-C2-C1 = 121.6(4); For [2][BF4]: P1-Sb1 = 3.321(1), P1-Sb1-C13 =
161.3(1), C1-Sb1-C7 = 106.2(1), C1-Sb1-C19 = 113.3(1), C7-Sb1-C19 = 115.4(1), P1-C2-C1 = 118.3(3) Sb1-C1-C2 = 119.8(3); For [3][BF4]2: Sb1-P1 = 3.922(1), Sb1-F6 =
3.038(2), C1-Sb1-C7 = 106.4(1), C1-Sb1-C19 = 123.7(1), C7-Sb1-C13 = 108.3(1), C2-P1-C25 = 104.8(2), C2-P1-C31 = 107.6(2), C25-P1-C31 = 111.6(2).
hydrolysis in the presence of adventitious water.31 No such The crystal structures of [3][BF4], [4][BF4], and [5][BF4]2 have
tendency toward decomposition was observed in the case of been determined (Figure 3). The first notable feature of these
[5]2+. All new salts have been fully characterized. The structures concerns the short contacts that may exist between
phosphonium units in [3]+ and [5]2+ give rise to a single 31P the anion and the group 15 atoms. While both [3][BF4] and
NMR resonance at 23.6 ppm and 26.5 ppm, respectively. The [4][BF4] are free of such short contacts, one of the two anions
1
associated H NMR methyl resonance appears as a doublet at in [5][BF4]2 forms a Sb-F interaction of 3.038(2) Å. The
3.14 ppm (2JH-P = 13.0 Hz) and 2.50 ppm (2JH-P = 13.3 Hz), presence of this short interaction reflects the enhanced Lewis
respectively. In the case of [4][BF4], the 31P NMR resonance at acidic or pnictogen bond donor character of the antimony
11.4 ppm is shifted significantly downfield with respect to that atom in this dicationic derivative. A second noteworthy point
of PPh3 (-6 ppm). We assign this downfield shift to the relates to the P-Sb separation of 3.321(1) Å in the structure of
presence of a donor-acceptor interaction between the Lewis [4][BF4]. Although this distance is longer than that in o-
basic phosphine and the Lewis acidic antimony centre. The 31
P
C6H4(PPh2)((SbPh2)(O2C6Cl4)) (3.0268(12) Å), the P1-C2-C1
NMR chemical shift of [4]+ can be compared to the value angle (118.3(3)°) is smaller than 120°, indicating attraction of
measured in o-C6H4(PPh2)((SbPh2)(O2C6Cl4)) (25.5 ppm) which the two group 15 centres. We interpret this small distortion as
was also shown to possess such an intramolecular PSb manifesting the presence of a weak intramolecular PSb
bond.13
interaction (see SI). This weak P-Sb interaction is reminiscent
of that present in naphthalene based-systems32 such as F23 and
G33. Given the constraints imposed by the naphthalene
backbone, these dative interactions are shorter and thus likely
stronger.
-
-
-
BF4
BF4
BF4
Me
P
Ph
Me
Ph
Ph
Ph
Ph
Ph
Ph
Sb
Ph
Ph
Sb
P
Ph
Ph
1
2
3
[ ][BF4]
[ ][BF4]
[ ][BF4]
Ph
Ph
Ph
Ph
Ph
Ph
-
-
-
Sb
Sb
Ph2P
(iPr)2P
BF4
2BF4
2BF4
Cl
Ph
Me Ph
Me Ph
Ph
Ph
Ph
Ph
P
Sb
Ph
Ph
Ph
P
Sb
Sb
Sb
Ph
Ph
Ph
Ph
Me
F
G
4
[ ][BF4]
5
6
[ ][BF4]2
[ ][BF4]2
In the next phase of this study, we decided to test the cations
represented in Figure 2 as catalysts for the transfer
hydrogenation reaction known to occur between Hantzsch
ester and quinolines.34 The first set of reactions was carried
out in CDCl3 with a 5 mol% catalyst loading using 2-phenyl-
Figure 2. Cationic phosphorus and antimony Lewis acids investigated herein.
o-(Ph2P)C6H4Li + Ph3SbBr2
P
Sb
Ph2
Ph2
Et2O/THF, -78 o
C
Br
quinoline as
a
substrate. We found that the
AgBF4
Me3OBF4
CH2Cl2
P
Sb
Ph3
Ph2
4
5
[ ][BF4]2
[ ][BF4]
1) MeI
2) NaBF4
monophosphonium cations [1][BF4] and [3][BF4] were
essentially inactive (entries 1 and 3). Conversely, the reaction
proceeded smoothly in the presence of the monostibonium
salts [2][BF4] and [4][BF4], reaching 26% and 24% conversion,
respectively, after 1 hour (entries 2 and 4). The comparable
activity of these two cations shows that the weak P → Sb in
CH2Cl2
3
[ ][BF4]
4
-Br
Scheme 1. Synthesis of [3]BF4] (left), [4]BF4] (right) and [5]BF4]2 (right).
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 5
Dalton Transactions
Please do not adjust margins
Journal Name
ARTICLE
[4]+ has no significant influence on the reactivity of the that would precede transfer of a hydride from the Hantzsch
View Article Online
stibonium cation. The results obtained with these four ester.37 We first investigated [5]2+ usingDqOuI:in10o.l1i0n3e9/aCs9DaTm01o35d7eAl
monocations show that the antimony species are significantly substrate. The lowest energy structure shows coordination of
more active, in line with their documented intrinsic higher the quinoline molecule to the antimony centre via a Sb-N
Lewis acidity.16, 35, 36 With the view of verifying that the Lewis contact of 3.11 Å. The value of the  angle (172.0) defined in
acidity of the stibonium cation would be enhanced by a nearby Figure 5 indicates that the antimony atom is positioned along a
secondary cationic moiety, we became eager to evaluate direction aligned with the nitrogen lone pair. As confirmed by
[5][BF4]2 (entry 5) which indeed afforded a significantly higher Natural Bond Orbital calculations, the two atoms are
conversion (61% yield) than those obtained with the connected by a donor-acceptor interaction of lp(N) → *(Sb-C)
monostibonium salts [2][BF4] and [4][BF4]. The use of the bis- character. As suggested by application of the NBO deletion
stibonium salt [6][BF4]2 afforded a further enhancement in protocol, these interactions stabilize the complex by Edel = 12.6
activity, with a conversion of 90% after 1 hour (entry 6). The kcal/mol. No short contacts are observed between the
greater activity of [6]2+ is assigned to the presence of two quinoline nitrogen and the potentially acidic phosphorus
adjacent Lewis acidic antimony centres which can atom.38, 39 However, the quinoline appears to be engaged in a
cooperatively activate the substrate. The previous -stacking interaction with a phosphorus-bound phenyl ring
characterization of [6-2-DMF]2+, an adduct in which the DMF (Figure 4). This interaction may help orient the substrate
carbonyl oxygen atom interacts with the two antimony atoms, within the bifunctional pocket of [5]2+, thereby assisting
illustrate this possibility.26 We have also tested B as a catalyst coordination of the nitrogen atom to the the Lewis acidic
(entry 7) and found that it afforded only a ~5% yield after 1 antimony center. In [6]2+ - quinoline, the quinoline is
hour, which is just slightly higher than for the uncatalyzed preferentially bound to one of the antimony atoms (Sba) with
reaction (entry 8). This low yield underscores the role played which it forms an Sba-N contact of 3.16 Å, close the
by the cationic nature of the Lewis acid in these reactions. We corresponding distance in [5]2+ - quinoline. The value of the 
have also studied these group 15 catalysts in the angle (169.7) is also close to that in [5]2+ - quinoline. As
hydrogenation of 3-bromoquinoline,
a
more reactive indicated by the Sba-N-Sbb angle of 77.4 (defined as  in
substrate. The results (entries 9-16), although less contrasted Figure 4), the second antimony atom Sbb is positioned along a
than those obtained with 2-phenylquinoline, support the direction approximately perpendicular to the Sba-N vector,
above conclusions that dicationic systems are the most active leading to a longer Sbb-N distance of 3.58 Å. These Sb-N
and that stibonium cations supersede their phosphonium distances are both within the sum of van der Waals radii of the
counterparts.
two elements (vdWR(Sb,N) = 4.13 Å),40 suggesting donor-
acceptor bonding. Congruent with this view, an NBO analysis
indicates that the quinoline molecule interacts with the two
antimony centres via lp(N) → *(Sb-C) interactions which
contribute Edel = 10.9 kcal/mol to the stability of the complex.
We also note that, as in [5]2+ - quinoline, the quinoline is
engaged in a -stacking interaction with a phenyl ring bound
to Sbb. Last, we note that the electrostatic potential surface of
[5]2+ and [6]2+ shows a distinct, yet buried positive area that
corresponds to the intersecting -holes of the pnictogen
atoms (Figure 4). These features indicate that these adducts
are also stabilized by an ionic contribution. We propose that
the cooperativity of the two Lewis acidic pnictogen units is at
the origin of the superior catalytic activity of [5]2+ and [6]2+.
Similar effects have been invoked in the case of
benzodiselenazoles which also act as catalysts for the transfer
hydrogenation of quinolines.34, 37
Table 1. Transfer hydrogenation of quinolines.
EtOOC
COOEt
N
Y
X
Y
X
H
CDCl3, 1 h
N
N
H
Q1
Q2
: X =Ph, Y =H
: X =H, Y =Br
Entry
1
2
3
4
5
6
7*
8
Cat.
[1][BF4]
[2][BF4]
[3][BF4]
[4][BF4]
[5][BF4]2
[6][BF4]2
B
Substrate
Q1
Time
1 h
1 h
1 h
1 h
1 h
1 h
1 h
1 h
Yield
<1%
26%
< 1%
24%
61%
90%
5%
Q1
Q1
Q1
Q1
Q1
Q1
Q1
3%
-
9
Q2
Q2
Q2
Q2
Q2
Q2
Q2
Q2
10 min
10 min
10 min
10 min
10 min
10 min
10 min
10 min
23%
60%
< 1%
51%
76%
86%
30%
< 1%
[1][BF4]
[2][BF4]
[3][BF4]
[4][BF4]
[5][BF4]2
[6][BF4]2
B
10
11
12
13
14
15
16
-
Lastly, DFT calculations were used to simulate the double
activation of the substrate by the dicationic systems, a step
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 4 of 5
ARTICLE
Journal Name
5 2+
6.
7.
8.
S. S. Chitnis, N. Burford, R. McDonald and M. J. Ferguson,
[ ] - quinoline
View Article Online
5 2+
-stacking ESP of [ ]
C4
Ph
N
Inorg. Chem., 2014, 53, 5359-5372.
DOI: 10.1039/C9DT01357A
P

Sb
Sb
K. Singhal, R. N. P. Yadav, P. Raj and A. K. Agarwal, J.
Fluorine Chem., 2003, 121, 131-134.
M. Hirai and F. P. Gabbaï, Angew. Chem. Int. Ed., 2015, 54,
1205-1209.
Ph
N
Sb
P
Ph
Ph

Ph
Me
P
 = 172.0,  = 60.9
9.
10.
M. Hirai and F. P. Gabbaï, Chem. Sci., 2014, 5, 1886-1893.
C.-H. Chen and F. P. Gabbaï, Angew. Chem. Int. Ed., 2017,
56, 1799-1804.
C. R. Wade and F. P. Gabbaï, Organometallics, 2011, 30,
4479-4481.
L. Greb, Chem. Eur. J., 2018, 24, 17881-17896.
D. Tofan and F. P. Gabbaï, Chem. Sci., 2016, 7, 6768-6778.
S. Benz, A. I. Poblador-Bahamonde, N. Low-Ders and S.
Matile, Angew. Chem. Int. Ed., 2018, 57, 5408-5412.
M. Yang, D. Tofan, C.-H. Chen, K. M. Jack and F. P. Gabbaï,
2018, 57, 13868-13872.
I.-S. Ke, M. Myahkostupov, F. N. Castellano and F. P.
Gabbaï, J. Am. Chem. Soc., 2012, 134, 15309-15311.
M. Hirai, M. Myahkostupov, F. N. Castellano and F. P.
Gabbaï, Organometallics, 2016, 35, 1854-1860.
C. R. Wade, I.-S. Ke and F. P. Gabbaï, Angew. Chem. Int.
Ed., 2012, 51, 478-481.
S. S. Chitnis, H. A. Sparkes, V. T. Annibale, N. E. Pridmore,
A. M. Oliver and I. Manners, Angew. Chem. Int. Ed., 2017,
56, 9536-9540.
M. Yang, N. Pati, G. Belanger-Chabot, M. Hirai and F. P.
Gabbaï, Dalton Trans., 2018, 47, 11843-11850.
A. Baba, M. Fujiwara and H. Matsuda, Tetrahedron Lett.,
1986, 27, 77-80.
M. Fujiwara, A. Baba and H. Matsuda, J. Heterocycl.
Chem., 1988, 25, 1351-1357.
R. Arias-Ugarte, D. Devarajan, R. M. Mushinski and T. W.
Hudnall, Dalton Trans., 2016, 45, 11150-11161.
R. Arias-Ugarte and T. W. Hudnall, Green Chemistry, 2017,
19, 1990-1998.
N. Li, R. Qiu, X. Zhang, Y. Chen, S.-F. Yin and X. Xu,
Tetrahedron, 2015, 71, 4275-4281.
M. Hirai, J. Cho and F. P. Gabbaï, Chem. Eur. J., 2016, 22,
6537-6541.
B. Pan and F. P. Gabbaï, J. Am. Chem. Soc., 2014, 136,
9564-9567.
M. Yang and F. P. Gabbaï, Inorg. Chem., 2017, 56, 8644-
8650.
C. H. Winter, W. R. Veal, C. M. Garner, A. M. Arif and J. A.
Gladysz, J. Am. Chem. Soc., 1989, 111, 4766-4776.
W. E. McEwen, G. H. Briles and B. E. Giddings, J. Am.
Chem. Soc., 1969, 91, 7079-7084.
M. Abdalilah, R. Zurawinski, Y. Canac, B. Laleu, J. Lacour,
C. Lepetit, G. Magro, G. Bernardinelli, B. Donnadieu, C.
Duhayon, M. Mikolajczyk and R. Chauvin, Dalton Trans.,
2009, DOI: 10.1039/B903933C, 8493-8508.
J. Brünig, E. Hupf, E. Lork, S. Mebs and J. Beckmann,
Dalton Trans., 2015, 44, 7105-7108.
6 2+
[ ] - quinoline
-stacking
6 2+
C4
N
ESP of [ ]
Sba
11.

Me
Sbb
Ph
N
Sba  Sbb
Ph
Ph
Ph
Me
12.
13.
14.
 = 169.7,  = 77.4
15.
16.
17.
18.
19.
Figure 4. Optimized structure of [
5]2+ - quinoline and [6]2+ - quinoline. NBOs of the
nitrogen lone pair (lp(N)) and the major accepting antibonding orbital (*(Sb-C)) are
also shown (isovalue = 0.05). The inset shows that ESP of [5]2+ and [6]2+ (isosurface:
0.005 au; red: 0.18 au, blue: 0.32 au).
In conclusion, we have synthesized and studied a series of
bifunctional ortho-phenylene phosphorus and antimony
derivatives in which one if not both of the group 15 centres
exist as pnictogenium cations. Using the transfer
hydrogenation of quinolines with Hantzsch ester as a
benchmark, we find that the dicationic derivatives [5][BF4]2
and [6][BF4]2 are the most active. This reactivity illustrate the
benefits that result from the introduction of a second cationic
functionality in these derivatives. The higher catalytic activity
displayed by the bis-stibonium dication [6]2+ may be assigned
to the juxtapositions of two Lewis acidic antimony(V) units that
may cooperatively activate the substrate. Last but not least,
the results obtained in this study show that simple stibonium
cations such as [2]+ ([SbPh4]+) are significantly more active than
neutral electron-deficient stiboranes such as B.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
This work was supported by the National Science Foundation
(CHE-1566474), the Welch Foundation (A-1423), and Texas
A&M University (Arthur E. Martell Chair of Chemistry).
References
1.
M. Baaz, V. Gutmann and O. Kunze, Monatsh. Chem.,
1962, 93, 1142-1161.
32.
33.
2.
3.
K. Ishihara, 2000.
G. A. Olah and R. H. Schlosberg, J. Am. Chem. Soc., 1968,
90, 2726-2727.
B. A. Chalmers, M. Bühl, K. S. AthukoralaꢀArachchige, A.
M. Z. Slawin and P. Kilian, Chem. Eur. J., 2015, 21, 7520-
7531.
4.
5.
R. Qiu, Y. Chen, S.-F. Yin, X. Xu and C.-T. Au, RSC Advances,
2012, 2, 10774-10793.
A. P. M. Robertson, S. S. Chitnis, H. A. Jenkins, R.
McDonald, M. J. Ferguson and N. Burford, Chem. Eur. J.,
2015, 21, 7902-7913.
34.
35.
S. Benz, J. Mareda, C. Besnard, N. Sakai and S. Matile,
Chem. Sci., 2017, 8, 8164-8169.
K. D. Moffett, J. R. Simmler and H. A. Potratz, Anal. Chem.,
1956, 28, 1356-1356.
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 5
Dalton Transactions
Please do not adjust margins
Journal Name
ARTICLE
36.
37.
38.
39.
40.
J. S. Jones, C. R. Wade, M. Yang and F. P. Gabbaï, Dalton
Trans., 2017, 46, 5598-5604.
View Article Online
DOI: 10.1039/C9DT01357A
S. Benz, J. López-Andarias, J. Mareda, N. Sakai and S.
Matile, Angew. Chem. Int. Ed., 2017, 56, 812-815.
J. M. Bayne and D. W. Stephan, Chem. Soc. Rev., 2016, 45,
765-774.
K. D. Reichl, N. L. Dunn, N. J. Fastuca and A. T. Radosevich,
J. Am. Chem. Soc., 2015, 137, 5292-5295.
S. Alvarez, Dalton Trans., 2013, 42, 8617-8636.
Y
EtO2C
2
CO2Et
X
R
N
N
Y
X
Sb
R
+
H
R
-holes
of [o-C6H4(SbMePh2)2]2+
N
H
= PR4 or SbR4
+
Bifunctional group 15 dications are effective transfer hydrogenation
catalysts, the activity of which cumlinates in the case of the bis-
stibonium dication [o-C6H4(SbMePh2)2]2+.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins