Unravelling a general mechanism of converting ionic B/N complexes into neutral B/N analogues of alkanes: H: δ +?Hδ - ydrogen bonding assisted dehydrogenation

Article abstract of DOI:10.1039/c9cc07133d

Long-sought mechanisms for the conversion of diammoniate of diborane ([NH₃BH₂NH₃]⁺[BH₄]^-) into NH₃BH₃ and [NH₂BH₂]_n as well as ammonium aminodiborane ([NH₄]⁺[BH₃NH₂BH₃]^-) into a butane analogue, NH₃BH₂NH₂BH₃, have been elucidated on the basis of extensive experimental and theoretical studies. The [NH₄]⁺ ammonium cation and the (η²-H₂)BH₂R moiety are found to be critical in B/N chain expansion.

Full text of DOI:10.1039/c9cc07133d

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DOI: 10.1039/C9CC07133D
Journal Name
COMMUNICATION
Unraveling a general mechanism of converting ionic B/N
complexes into neutral B/N analogues of alkanes: H H
δ+
δ–
dihydrogen bonding assisted dehydrogenation
Received 00th January 20xx,
Accepted 00th January 20xx
a
b
c,d
a
*b
*c
*a,b
Xi-Meng Chen, Si-Cong Liu, Cong-Qiao Xu, Yi Jing, Donghui Wei, Jun Li and Xuenian Chen
DOI: 10.1039/x0xx00000x
www.rsc.org/
3
The long-sought mechanisms for the conversion of diammoniate of on producing long-chain B-N polymers via catalysts and on
+
-
8f,g
diborane ([NH
as ammonium aminodiborane ([NH
analogue, NH BH NH BH
3
BH
2
NH
3
] [BH
4
] ) into NH
3
BH
3
and [NH
2
BH
2
]
n
as well exploring the thermal decomposition mecnahnism.
]+[BH
NH BH
2 3
] ) into butane Unfortunately, the formation mechanisms of aforementioned
-
4
3
3
2
2
3
, have been elucidated on the basis of reactions remain largely elusive, which precludes rational
+
5,6
extensive experimental and theoretical studies. The [NH
ammonium cation and ( -H
in B/N chain expansion.
4
]
design of materials with B/N analogs of alkane.
2
δ–
2
)BH

R moiety are found to be critical
With the recognition of the nucleophilicity of B-H bonding
pair electrons, we recently developed controlled synthetic
7
methods to expand the length of B/N chain anions,
Boron and nitrogen are the neighboring elements of carbon. As
a result, the isoelectronic relationship between B-N and C-C
couples gives rise to an interesting class of B/N chain complexes
-
-
[
BH
3 2 2 n 2 3 3
(NH BH ) H] (n = 1, 2, and 3) and [HB(NH BH ) ] , through
+
-
the reaction of AB with Na H by modulating the reactant ratios
and temperatures. Their reaction mechanisms were also
elucidated experimentally and computationally. In the current
9
that are analogous to linear alkanes, for instance, H-[-NH2BH
2
-
9
1
-3
n
] -H versus H-[-CH
2 2
CH -]
n
-H.
Though B/N analogues of
work, we present the experimental and theoretical study on the
alkanes have similar structures with alkanes, their properties
are distinctly different from those of alkanes duo to the
different electronegativity between B and N atoms. In general,
B-N, N-H, and B-H are polar bonds and their complexes are more
active.1a Especially noteworthy is the strong interaction
mechanisms of the B-N bond formation via dehydrogenation
δ+
δ–
4,10
assisted by H H interaction, dihydrogen bond (DHB). This
DHB interaction widely exists in ammonium salts of anionic or
cationic B/N chain species of borohydrides.
There are several pathways for B-N bond formation. Among them,
the simplest is to construct the B-N bond via the thermal

between a positively charged, protic hydrogen in N-H and a

negatively charged, hydridic hydrogen in B-H of amine borane
+
-
dehydrocoupling reaction of ammonium borohydride ([NH
AB), which can be rapidly synthesized through a metathesis
reaction of the ammonium salts and alkali metal borohydrides at low
4 4
] [BH ] ,
4
complexes. It is rather difficult to synthesize long-chain B/N
H
2
analogs of alkanes. Currently, several landmark B/N amine
borane complexes, such as the diammoniate of diborane
5b,c,11
temperature.
Using this reaction of H
2
AB, AB was first
+
-
5a
(
[NH
3
BH
2
NH
3
] [BH
4
] , DADB), ammonia borane (NH
3
BH
3
,
5b,c
synthesized (see eqn (1) below).
This strategy is rationally
5
b,c
5d
AB), aminodiborane (NH
complexes6 were synthesized, including two- to seven-
membered B/N chain complexes.
2
B
H
2 5
, ADB), and several B/N chain
envisaged to apply in other ammonium salts of anionic and cationic
B/N chain species of borohydrides for synthesis of long B/N chain
complexes. However, this reaction has been found to be suitable for
6
,7a,8a-e
Many groups worked
the
[NH
NH BH
dehydrocoupling
of
ammonium
aminodiborane
BH (i.e.,
]+[BH
NH
NH
BH
] , AADB) to produce H(NH
-
(
4
3
2
3
2
2 2
) H
a. Henan Key Laboratory of Boron Chemistry and Advanced Energy Materials,
12
13
3
2
2
BH
3
) , but not for DADB, even though DADB and AADB
School of Chemistry and Chemical Engineering, Henan Normal University,
Xinxiang, Henan 453007, China. E-mail: xnchen@htu.edu.cn (X.C.)
College of Chemistry and Molecular Engineering, Zhengzhou University
δ+
δ–
are ionic isomers and the H H interaction exists in both
complexes. The AADB and DADB complexes are stable in solutions at
low temperatures
reactions with increasing temperature.
b.
Zhengzhou, Henan 450001, China. E-mail: donghuiwei@zzu.edu.cn (D.W.)
Department of Chemistry and Key Laboratory of Organic Optoelectronics &
12,13
but undergo different dehydrogenation
c.
1
2-14
Molecular Engineering of Ministry of Education, Tsinghua University, Beijing
While AADB can
1
00084, China. E-mail: junli@tsinghua.edu.cn (J.L)
dehydrogenate
1
equiv. of
H
2
to form NH
3
BH NH
2 2
BH
3
in
d.
Department of Chemistry, Southern University of Science and Technology,
o
12
tetrahydrofuran (THF) at -18 C (eqn (2)), DADB transforms into AB
and [BH
observations suggest that only NH
Shenzhen 518055, China
o
13
†Electronic Supplementary Information (ESI) available: Experimental procedures,
2 2
NH ]
polymer in THF at -10 C (eqn (3)). These
n
NMR spectra,and IR spectra. See DOI:10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
+
4
salts of anionic B-N-B chain
J. Name., 2013, 00, 1-3 | 1
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Page 2 of 4
COMMUNICATION
Journal Name
dehydrocoupling leads to the formation of N-B bond through
View Article Online
DOI: 10.1039/C9CC07133D

G (kcal/mol)
dehydrogenation to extend the B/N chain, whereas the salt species
1
.66
2.51
1
.57
.85
.7
-
with a cationic N-B-N chain and a [BH
4
] anion cannot extend the B/N
0
9
2.30
1.77
chain. The different dehydrogenation mechanisms of these two kinds
of isomeric salts remain a puzzle so far, despite its importance in
1
2.29
.63
1.79
TS6 NH3
THF 3.9
TS7
2.5
1
1-14
1.9
design of long-chain B/N compounds.
0.0
AADB
TS8
BH3NH2BH2•H2
2.32
-4.9
2.04
H2
TS9
+
]- → NH
NH3
[
[
[
NH
NH
NH
4
4
3
] [BH
4
3
-
BH
3
+ H
2
(1)
(2)
(3)
+
] [BH
3
NH
2
+
3
BH ] → NH
3
BH
BH
2
NH
2
BH
3
+ H
2
THF
NH3
-
BH
2
3 4
NH ] [BH ] → NH
3
3
+ 1/n [NH
2
BH
]
2 n
+ H
2
THF
NH3BH2NH2BH3
-22.9
-23.6
THFBH2NH2BH3
In order to explore the reaction mechanisms of AADB and
DADB, we performed density functional theory (DFT) study
using Gaussian 09 program. The proposed mechanisms for the
dehydrogenation of DADB and AADB are consistent with the
-
33.1
NH BH +NH BH
3
3
2
2
1
5
+
B C NOH
1
2-13
Formation of NH3BH2NH2BH3
experimental results.
conversion of DADB is shown in Fig. 1. The reaction in the Fig. 2 The possible reaction pathways for the transformations
3
presence of THF is initialized by the interaction between one from AADB to AB, NH BH and NH BH NH BH .
The possible pathway for the
2
2
,
3
2
2
δ+
+
protic H from the terminal NH
3
in [NH
3 2 3
BH NH ] cation and
δ–
-
one hydridic H from [BH
molecule of H and formation of NH
base with a lone pair on the ending NH
4
] anion, leading to the release of a
Indeed, these theoretical results agree well with the
(a reactive Lewis experimental results that DADB can transform into AB and
2
3
BH
2
NH
2
o
13
2 3 2 2 n
) and THF·BH via [BH NH ] polymers in THF at -10 C. The decomposition of
1
1
transition states TS1 (17.7 kcal/mol) and TS2 (1.4 kcal/mol). In DADB with increasing temperature was monitored by B NMR
+
-
TS1, the proton transfer from [NH
3
BH
2
NH
3
] cation to [BH
4
]
in our previous work, in which the formation of AB was
1
3
anion and the subsequent formation of a dihydrogen moiety confirmed. We have repeated this reaction and the AB and
2
(
 -H
2
)BH
3
play a central role. The THF solvent helps [NH
intermediate via The ratio of the resulting AB and [NH
donor-acceptor interaction to yield THF·BH . The energy For the conversion of AADB into NH
barriers of the two transitionstates are easy to overcome under colleagues studied the mechanism in 2016 although the effect
2
BH ]
2 n
products are isolated and characterized (Fig. S1-3).
BH is roughly 1:1.
BH NH BH , Chen and
stabilization of the resulting Lewis acidic BH
3
2
2 n
]
3
3
2
2
3
1
2
the reaction condition. Subsequently, two possible competing of THF solvent was not considered. Given the importance of
pathways were considered in the presence of THF solvent: one solvent in these reactions, we explicitly include the THF solvent
leading to form NH
in Fig. 1), and the other leading to the formation of AB and Fig. 2 illustrates the two possible competitive pathways
NH BH via transition states TS4 and TS5 (black part in Fig. 1). associated with the conversion of AADB to AB, NH BH , and
Thus formed monomer of NH BH can polymerize easily to form NH BH NH BH . Firstly, as in the TS1 of DADB conversion, a
As shown in Fig. 1, the energy barrier of TS3 dihydrogen moiety ( -H
3 2 2 3
BH NH BH via transition state TS3 (red part in the present work to elucidate the role of the weak Lewis base.
2
2
2
2
2
2
3
2
2
3
1
6
2
the [NH
(
(
2 2 n
BH ] .
2
)BH
2
–R (R = NH
2
BH
3
) was formed via
δ+
+
δ–
11.9 kcal/mol, Table S1) is obviously higher than those of TS4 the interaction between one H from [NH
0.5 kcal/mol) and TS5 (8.5 kcal/mol), so AB and NH
4
] cation and one H
-
2
BH
2
should from BH
3
in [BH NH
3 2
BH
3
] anion, leading to the release of one
be the main products with DADB as the starting point.
molecule of H
2
and the formation of THF·BH
NH BH
2 2 3
and NH
3
in
the presence of THF via transition states TS6 and TS7. The role
2

G (kcal/mol)
of THF is to assist the H
release from ( -H
)BH
–R via donor-
2
2
2
1
.80
0
.83
.88
.47
7.7
TS1
acceptor interaction. The energy barriers of TS6 and TS7 are 9.7
and 2.0 kcal/mol (Table S1), respectively, which indicate that H
can desorb smoothly upon formation. After that, two pathways
are considered according to the availability of different B atoms
1
.81
1
2
.44
1
1
2
1
TS2
6.1
14.7
pre-TS2
2
.03 2.42
.5
TS3
4
for attack of the resulting NH
formed via transition state TS8 with an energy barrier of 25.4
kcal/mol when NH attacks the B atom of BH group (red part in
Fig. 2); while NH BH NH BH is formed via transition state TS9
with an energy barrier of 18.0 kcal/mol when NH binds to the
B atom of BH (THF) moiety (black part in Fig. 2). Obviously, the
formation of NH BH NH BH oligomer is energetically more
favourable than the AB and NH BH when AADB is used as a
starting material and THF as a solvent.
3 2 2
. Here AB and NH BH can be
0.0
H2
2.06
2.37
DADB+THF
2.42
-
7.4
NH3BH2NH2
THF•BH3
-6.9
TS4
-
8.7
NH2BH2 TS5
17.2
NH +THF•BH
3
3
+
THF
3
2
2
3
-
3
-
20.8
THF
3
3
NH3BH2NH2BH3
2
-30.3
3
3
2
3
NH3BH3
2
2
BCNO H
Formation of NH3BH3
Fig. 1 The possible reaction pathways for the transformations
from DADB to AB, NH BH , and NH BH NH BH
Fig. 3 The 11B NMR spectra of the products when (a) DADB and
2
2
3
2
2
3
.
3 2
(b) AADB dehydrogenate in THF with the presence of (CH ) NH.
2
| J. Name., 2012, 00, 1-3
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Journal Name
COMMUNICATION
c, d
d
we
have
synthesized
its
borohydride
isomer,
View Article Online
DOI: 10.1039/C9CC07133D
c
+
-
[
NH
3
BH NH BH NH ] [BH ] . It is found that the reaction of
2
2 2 3 4
(
b)
NH
NH
NH
3
3
3
BH
BH
2
NH
NH
2
BH
BH
3
and HCl results in the formation of
Cl (eqn (S1), Fig. S5-7), which then reacts with
2
2
2
o
+
-
in THF at 0 C to produce [NH
BH NH
by the metathesis reaction of [NH
NaBH in liquid ammonia (eqn (S3)). Notably, this cationic five-
membered B/N chain borohydride salt is only stable at lower
3
BH
BH
BH
2
NH
NH
NH
2
BH
]+[BH
BH
2
NH
3
] Cl (eqn (S2)
a
b
-
Fig. S8-10). Finally, the [NH
3
2
2
2
3
4
] is prepared
+
-
3
2
2
2 3
NH ] Cl with
4
(a)
temperatures and starts to decompose to AB and [NH
2
BH
2
]
n
at
o
-40 C (eqn (5), Fig. S11, S13 and S14). It is highly likely that the
a, NH
3
BH
3
;
b, (CH
3
)
2
NHBH
3
;
c, NH
3
BH
2
NH
2
BH
3
;
d,
mechanism of the conversion of the cationic five-membered
(
CH NHBH NH BH .
3
)
2
2 2 3
B/N chain borohydride is similar to the decomposition of DADB,
2
where the proton can easily transfer from NH
)BH –R and release H
3
to form ( -
In the proposed mechanisms of dehydrogenation of DADB
and AADB, the THF·BH and THF·BH NH BH are formed,
respectively, as the intermediates from which different
products (AB and NH BH NH BH ) are produced. Hence the
experimental evidence is critical in confirming this DHB-assisted
dehydrogenation mechanism. In order to corroborate these
intermediates, we have designed experiments by using
H
2
2
2
via THF coordination to BH
2
–R.
3
2
2
3
]+[BH
]- →
[
[
NH
NH
4
3
NH
2
BH
2
NH
2
BH
3
3
2
2
3
NH
BH
NH
+ 2/n [NH
BH
NH
BH
BH
+ H
(4)
(5)
3
2
2
2
2
3
2
]+[BH ]- →
3 2
BH NH
2
BH
2
NH
3
4
NH
3
BH
3
2
2
]
n
+ H
2
dimethylamine ((CH
:5 molar ratio as starting materials to examine the
dehydrogenation process. For the DADB and DMA mixture,
CH NHBH and AB are found after reaction, as revealed by the
3
)
2
NH, DMA) mixing with DADB or AADB at
+
The above results indicate that the NH
4
cation plays a critical
3
role in the B/N chain expansion. We have therefore further
examined the conversion of other ionic, NH
complexes, into B/N analogues of alkanes. To this end, we also
+
4
-free B/N
(
)
3 2
3
1
1
1
11
B and B{ H} NMR spectra (Fig. 3a and S4a). This observation
unequivocally proves that THF·BH is indeed formed as the
intermediate, which further competitively reacts with DMA and
in-situ formed NH to generate (CH NHBH and AB. For the
AADB and DMA mixture, (CH NHBH NH BH and
NH BH NH BH are identified after reaction (Fig. 3b and S4b).
Similarly, the resulting THF·BH NH BH intermediate reacts with
additional DMA and NH to produce (CH NHBH NH BH and
NH BH NH BH , respectively. These experimental results
+
-
synthesized two new compounds [NH
3
BH
]- by the metathesis
2 3 3 2 2 2 3
BH NH ] [BH NH BH NH BH
2 3 3 2 3
NH ] [BH NH BH ]
3
and [NH
reactions between anionic B/N chain species and cationic B/N
+
3
3
)
3 2
3
chain species. The starting materials Na [BH
+
NH
] Cl were prepared
according to our recently reported work and the literature
2 3
BH ] ,
-
3
)
3 2
2
2
3
+
-
+
-
3 2 2 2 3 3 2 3
Na [BH NH BH NH BH ] and [NH BH NH
3
2
2
3
2
2
3
methods, respectively. The metathesis reactions (eqn (6) and
9,13
3
)
3 2
2
2
3
(
7)) were performed in liquid NH
reaction mixture was warmed up to room temperature until the
liquid NH volatilized completely, and THF was condensed into
3
at -78 C for 2 hours. Then the
o
3
2
2
3
provide clear evidence to support the aforementioned
mechanism.
3
the reaction mixture. Finally, the dehydrogenations were
completed with the formation of B/N neutral species (Fig. S15-
9) and the target products, neutral six- and eight-membered
B/N chain complexes, were not obtained. The results clearly
indicate that such ionic B/N complexes without involving NH
cation cannot be used for the B/N chain expansion.
The DHB-assisted dehydrogenation mechanism of DADB and
AADB appears to be a general one for boron-nitrogen hydrides
and can be used to interpret the dehydrogenation reactions of
other analogous compounds as well. In the base-promoted
1
+
4
6
anionic dehydropolymerization mechanism of Sneddon et al.,
base + AB (base)H + H
+
-
3 2
BNH and the latter initiates an AB
anionic polymerization reaction also via a DHB-assisted
+
-
+
]- →
2 3
BH
[
[
NH
NH
3
BH
2
NH
3
] Cl + Na [BH
3
NH
BH
NH
NH BH
+
- 9
dehydrogenation mechanism. In our reaction of AB and Na H ,
NH BH NH
-
3
2
+
2
3
+ [NH
BH NH
NH BH
2
BH
2 3
BH
2
]
n
+ NaCl + H
2
(6)
-
the hydridic H anion easily extracts a proton from AB through
+
]- →
3
BH
2
NH
3
] Cl + Na [BH
NH BH
3
2
2
the same DHB-assisted dehydrogenation mechanism, which
effectively facilitates the subsequent oligomerisation. As a
3
2
2
2
2
3 3 3
+ NH BH + NaCl (7)
+
-
further example, [NH
dehydrocoupling reaction at room temperature to form
H(NH BH H (i.e., NH BH NH BH NH BH ), a B/N analogues of
4 3 2 2 2 3
] [BH NH BH NH BH ] can undergo a
In conclusion, the mechanisms of the dehydrogenation of
DADB and AADB have been elucidated on the basis of
experimental and computational results. We find that the
2
)
2 3
3
2
2
2
2
3
8
c
hexane (eqn (4)). The dehydrogenation mechanism of
ammonium salt of the five-membered chain anion should be
similar to that of AADB, i.e., also involving a dihydrogenmoiety
2
2 2
formation of a dihydrogen moiety ( -H )BH R via proton
2
+
(
 -H
2
)BH
2
–R formed via proton transfer from [NH
4
]
to
-
[
BH NH
3
BH NH BH
2 2 2 3
] . To compare the dehydrogenation of the
ammonium salt with its ionic isomer of borohydride and further
to confirm the two different mechanisms as discussed above,
Scheme 1. The mechanisms for conversion of
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

NH BH + m/n [NHP2l
BH ] +
e
as
e
d
H
oC 2 hn eo mt Ca do mj u ms t margins
Page 4 of 4
3
3
2 n
[
H(NH BH ) NH ][BH ]
2 2 m 3 4
NH (BH NH ) BH + H2
3
2
2 m
3
Ionic isomers (m = 1, 2)
COMMUNICATION
Journal Name
NH (BH NH ) BH + H2
3
2
2 m
3
[
NH ][BH (NH BH ) H]
4
3
2
2 m
5
(a) A. Stock and E. Kuss,Ber. Dtsch. Chem. Ges.VieBw, A1rt9ic2le3O, n5lin6e,
NH BH + m/n [NH BH ] + H2
3
3
2
2 n
]+[BH
-
-
789-808; (b) S. G. Shore and R. W. Pa
DOI: 10.1039/C9CC07133D
955, 77, 6084-6085; (c) S. G. Shore and R. W. Parry, J. Am.
rry, J. Am. Chem. Soc.,
[
[
H(NH
NH
2
+
BH
] [BH
2
)
m
NH
3
4
]
into NH BH
3 3
2 2 n
and [NH BH ] , and
1
4
3
(NH
2
2 m
BH ) H] into NH
3
2 2 m 3
(BH NH ) BH (m = 1, 2).
Chem. Soc., 1958, 80, 8-12; (d) H. I. Schlesinger, D. M. Ritter
and A. B. Burg, J. Am. Chem. Soc., 1938, 60, 1296-1330.
W. C. Ewing, A. Marchione, D. W. Himmelberger, P. J. Carroll
and L. G. Sneddon, J. Am. Chem. Soc., 2011, 133, 17093-
transfer from the [NH
from NH to [BH NH BH ] anion in AADB trigger two kinds of
reactions as shown in Scheme 1. The study has been further
extended to the dehydrogenation of more complicated ionic
B/N complexes involving the five-membered B-N chain cation or
anion and the same conclusion were obtained. These results
3
BH
2
-
NH
3
]+ cation to [BH
4
]- in DADB and
6
7
+
4 3 2 3
1
7099.
(a) X.-M. Chen, N. Ma, Q.-F. Zhang, J. Wang, X. Feng, C. Wei,
L.-S. Wang, J. Zhang and X. Chen, J. Am. Chem. Soc., 2018, 140,
6
718-6726; (b) Q. Zhao, R. D. Dewhurst, H. Braunschweig and
X. Chen, Angew. Chem. Int. Ed., 2019, 58, 3268-3278.
2
8
(a) X. Chen, X. Bao, B. Billet, S. G. Shore and J.-C. Zhao, Chem.
Eur. J., 2012, 18, 11994-11999; (b) S. R. Daly, B. J. Bellott, D. Y.
Kim and G. S. Girolami, J. Am. Chem. Soc., 2010, 132, 7254-
demonstrate that the dihydrogen moiety ( -H
containing intermediate plays a central role in various reactions
2 2
)BH R
+
-
2
[
NH
where L and R are different ligands such as H or the various
BNH chain complexes. This DHB-assisted dehydrogenation
mechanism is likely a general dehydrogenation mechanism for
various BNH compounds. Solvents such as THF are helpful in
stabilizing the BH -type of Lewis acidic site so as to facilitate the
desorption of the formed H molecule. Our work provides
insights into the fact that the B/N chains can be extended by
adding nitrogen unit through dehydrocoupling of
corresponding ammonium salts, but cannot be extended by
adding boron unit through dehydrogenation of the
corresponding borohydrides or other B/N ionic complexes. This
work shows promises for the development of boron and
nitrogen chemistry, especially for developing experimental
methods for synthesis of long-chain B/N complexes. These
analogues of alkanes may become interesting materials in
chemistry and material science.
3 3 2 2 2 2 2 2
L] [BH R]  [NH L][( -H )BH R]  [NH L][BH R] + H ,
7
255; (c) W. C. Ewing, P. J. Carroll and L. G. Sneddon, Inorg.
Chem., 2013, 52, 10690-10697; (d) X. Chen, J.-C. Zhao and S.
G. Shore, J. Am. Chem. Soc., 2010, 132, 10658-10659; (e) X.
Chen, J. Gallucci, C. Campana, Z. Huang, H. K. Lingam, S. G.
Shore and J.-C. Zhao, Chem. Commun., 2012, 48, 7943-7945;
x
x
(f) W. R. H. Wright, E. R. Berkeley, L. R. Alden, R. T. Baker and
2
L. G. Sneddon, Chem. Commun., 2011, 47, 3177-3179; (g) S. S.
Mal, F. H. Stephens and R. T. Baker, Chem. Commun., 2011, 47,
2922-2924.
J. Wang, X.-M. Chen, S.-C. Liu, J. Zhang, D. Wei and X. Chen,
Dalton Trans., 2019, DT-COM-05-2019-002289, in peer review.
0 R. H. Crabtree, Science, 1998, 282, 2000-2001.
2
9
a
1
1
1 (a) H. Li, Q. Yang, X. Chen and S. G. Shore, J. Organomet.
Chem., 2014, 751, 60-66; (b) D. J. Heldebrant, A. Karkamkar, J.
C. Linehan and T Autrey, Energy Environ. Sci., 2008, 1, 156-
1
60.
1
1
1
2 W. Chen, H. Yu, G. Wu, T. He, Z. Li, Z. Guo, H. Liu, Z. Huang and
P. Chen, Chem. Eur. J.,2016, 22, 7727-7729.
3 H. K. Lingam, X. Chen, J.-C. Zhao and S. G. Shore, Chem. Eur. J.,
2
012, 18, 3490-3492.
4 (a) X. Chen, X. Bao, J-C. Zhao and S. G. Shore, J. Am. Chem.
Soc., 2011, 133, 14172-14175; (b) Y. Song, N. Ma, X. Ma, F.
Fang, X. Chen and Y. Guo, Chem. Eur. J., 2016, 22, 6228-6233;
This work was supported by the National Natural Science
Foundation of China (Grant Numbers. 21771057 to X.C.,
1645203 to J.L, and 21773214 to D.W.).
(c) V. S. Nguyen, M. H. Matus, D. J. Grant, M. T. Nguyen and
9
D. A. Dixon, J. Phys. Chem. A, 2007, 111, 8844-8856.
5 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A.
Robb, J. R. Cheeseman, G. Scalmani, V. Barone, G. A.
Petersson, H. Nakatsuji, X. Li, M. Caricato, A. V. Marenich, J.
Bloino, B. G. Janesko, R. Gomperts, B. Mennucci, H. P.
Hratchian, J. V. Ortiz, A. F. Izmaylov, J. L. Sonnenberg, D.
Williams-Young, F. Ding, F. Lipparini, F. Egidi, J. Goings, B.
Peng, A. Petrone, T. Henderson, D. Ranasinghe, V. G.
Zakrzewski, J. Gao, N. Rega, G. Zheng, W. Liang, M. Hada, M.
Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T.
Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, K. Throssell,
J. A. Montgomery Jr., J. E. Peralta, F. Ogliaro, M. J. Bearpark, J.
J. Heyd, E. N. Brothers, K. N. Kudin, V. N. Staroverov, T. A.
Keith, R. Kobayashi, J. Normand, K. Raghavachari, A. P.
Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, J. M.
Millam, M. Klene, C. Adamo, R. Cammi, J. W. Ochterski, R. L.
Martin, K. Morokuma, O. Farkas, J. B. Foresman and D. J. Fox,
Gaussian16, Gaussian, Inc., Wallingford, CT, 2016.
1
Conflicts of interest
There are no conflicts to declare.
Notes and references
1
(a) Z. Liu and T. B. Marder, Angew. Chem. Int. Ed., 2008, 47,
42-244; (b) J. Li, S. M. Kathmann, H-S. Hu, G. K. Schenter, Tom
2
Autrey and M. Gutowski, Inorg. Chem., 2010, 49, 7710-7720.
T. Lorenz, A. Lik, F. A. Plamper and H. Helten, Angew. Chem.
Int. Ed., 2016, 55, 7236-7241.
(a) H. C. Johnson, A. P. M. Robertson, A. B. Chaplin, L. J. Sewell,
A. L. Thompson, M. F. Haddow, I. Manners and A. S. Weller, J.
Am. Chem. Soc., 2011, 133, 11076-11079; (b) A. P. M.
Robertson, E. M. Leitao, T. Jurca, M. F. Haddow, H. Helten, G.
C. Lloyd-Jones and I. Manners, J. Am. Chem. Soc., 2013, 135,
2
3
1
6 A. Staubitz, M. E. Sloan, A. P. M. Robertson, A. Friedrich, S.
Schneider, P. J. Gates, J. S. Günne and I. Manners, J. Am. Chem.
Soc., 2010, 132, 13332-13345.
1
2670-12683.
X. Chen, J.-C. Zhao and S. G. Shore, Acc. Chem. Res., 2013, 46,
666-2675.
4
2
4
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