Acid- and Base-Catalyzed Hydrolytic Hydrogen Evolution from Diboronic Acid

Article abstract of DOI:10.1002/ejic.202100093

The efficient production of H₂ from hydrogen-rich sources, particularly from water, is a crucial task and a great challenge, both as a sustainable energy source and on the laboratory scale for hydrogenation reactions. Herein, a facile and effective synthesis of H₂ and D₂ from only acid- or base-catalyzed metal-free hydrolysis of B₂(OH)₄, a current borylation reagent, has been developed without any transition metal or ligand. Acid-catalyzed H₂ evolution was completed in 4 min, whereas the base-catalyzed process needed 6 min. The large kinetic isotopic effects for this reaction with D₂O, deuteration experiments and mechanistic studies have confirmed that both H atoms of H₂ originate from water using either of these reactions. This new, metal-free catalytic system holds several advantages, such as high efficiency, simplicity of operation, sustainability, economy, and potential further use.

Full text of DOI:10.1002/ejic.202100093

Full Papers
doi.org/10.1002/ejic.202100093
1
2
3
4
5
Acid- and Base-Catalyzed Hydrolytic Hydrogen Evolution
from Diboronic Acid
Yi Wang+,[a] Jialu Shen+,[a] Yu Huang,[a] Xiang Liu,*[a] Qiuxia Zhao,[b] and Didier Astruc*[b]
6
7
8
9
The efficient production of H2 from hydrogen-rich sources,
particularly from water, is a crucial task and a great challenge,
both as a sustainable energy source and on the laboratory scale
for hydrogenation reactions. Herein, a facile and effective
synthesis of H2 and D2 from only acid- or base-catalyzed metal-
free hydrolysis of B2(OH)4, a current borylation reagent, has
been developed without any transition metal or ligand. Acid-
catalyzed H2 evolution was completed in 4 min, whereas the
base-catalyzed process needed 6 min. The large kinetic isotopic
effects for this reaction with D2O, deuteration experiments and
mechanistic studies have confirmed that both H atoms of H2
originate from water using either of these reactions. This new,
metal-free catalytic system holds several advantages, such as
high efficiency, simplicity of operation, sustainability, economy,
and potential further use.
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
Introduction
genation of a variety of substrates using water as the hydrogen
source,[8] and H2 has been found as intermediate[9] or product[10]
in some of these reactions.
Hydrogen-rich inorganic hydrides, metal hydrides, nanostruc-
tured materials, and chemical storage materials such as NH3BH3,
NaBH4 or related compounds based on boron[1] have been
regarded as most promising for chemical hydrogen storage
materials due to their high hydrogen content and easily storage
as solids.[2] Typically, hydrolysis of NH3BH3, NaBH4 or related
boron compounds catalyzed by optimized transition-metal
nanoparticles smoothly generates H2 under ambient
conditions.[3] On the other hand, several simple organic/
inorganic compounds such as for instance ethanol and water
have been shown to be useful in transfer hydrogenation, a very
rich organic chemistry field.[4] Indeed, the transport and current
laboratory use of explosive H2 is dangerous and hazardous. In
this respect, another commercially available class of boron
compounds, diboronic acid and esters, B2X4 (X=OH and
pinacolate, pin, respectively)[5] has shown great usefulness in
organic synthesis,[6] in particular for hydrogenation and cross
coupling with haloarenes producing arylboronic derivatives
that are well known as precursors of CÀ C bonds upon Miyaura-
Suzuki coupling.[7] These two diboron derivatives have indeed
largely been used in transition-metal-catalyzed transfer hydro-
The mechanism of H2 formation from water whereby both
hydrogen atoms from H2 are provided by water is therefore
clearly of different nature from those involving transition-metal
catalyzed hydrolysis of NH3BH3 or NaBH4 by which one H atom
is provided from water and the other one from NH3BH3 or
NaBH4.[10] Moreover, several reports have also appeared showing
useful substrate hydrogenation using these diboron com-
pounds with water as the only hydrogen source in the absence
of transition metal catalyst.[11] In a seminal article on the
reactions of B2Cl4, Wartik and Apple had noted: “B2(OH)4 is a
white solid which dissolved in a large excess of water to liberate
traces of hydrogen. The rate of hydrogen evolution was
increased somewhat by the addition of sulfuric acid and
became quite rapid on the addition of sodium hydroxide”.[12] In
parallel, Schlesinger had demonstrated metal-free acid-cata-
lyzed H2 formation from NaBH4, and, on the contrary, decrease
of hydrolytic activity in basic medium,[13] and Xu et al had
disclosed similar trends with hydrolytic H2 production from
NH3BH3.[14]
Given the interest in H2 evolution and the above applica-
tions of these diboron reagents involving their hydrolysis and
hydrogenation reaction, we have re-investigated the B2(OH)4
hydrolysis reaction in the absence of transition-metal catalyst.
Here we report the metal-free acid-catalyzed and base-
catalyzed H2 evolution upon hydrolysis of diboronic acid,
B2(OH)4. (Eq. 1). The mechanisms of these reactions are
proposed based on kinetic studies including kinetic isotope
effect (KIE) using D2O, in situ tandem reactions and deuteration
experiments. Compared to transition-metal nanoparticle-cata-
lyzed hydrolysis of B2(OH)4, this catalytic system also holds
several advantages, such as high efficiency, simplicity of
operation, sustainability, economy and potential further use.
[a] Y. Wang,+ J. Shen,+ Y. Huang, Prof. Dr. X. Liu
College of Materials and Chemical Engineering,
Key Laboratory of Inorganic Nonmetallic Crystalline and Energy Conversion
Materials, Material Analysis and Testing Center
China Three Gorges University,
Yichang, Hubei 443002, China
E-mail: xiang.liu@ctgu.edu.cn
https://www.x-mol.com/groups/liu_xiang
[b] Q. Zhao, Prof. Dr. D. Astruc
°
ISM, UMR CNRS N 5255, Univ. Bordeaux
351 Cours de la Libération, 33405 Talence Cedex, France
E-mail: didier.astruc@u-bordeaux.fr
http://astruc.didier.free.fr/
[+] These authors have contributed equally to this work and should be con-
sidered as co-first authors.
(1)
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/ejic.202100093
Eur. J. Inorg. Chem. 2021, 1–7
1
© 2021 Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/ejic.202100093
Results and Discussion
time vs. volume of H2 generated by acid-catalyzed diboronic
1
2
3
4
5
6
7
8
9
°
acid hydrolysis at different catalyst concentrations at 30 C and
Acid-catalyzed H2 evolution
the plot of H2 production rate vs. acid concentration in the
logarithmic scale. The slope of 0.20 demonstrates that the acid-
catalyzed hydrolysis of diboronic acid is first-order with respect
to the catalyst concentration. In diboronic acid concentration-
dependent hydrolysis, the acid concentration was kept at 0.5 M,
while the diboronic acid amounts were set at 0.5, 0.75, 1.0 and
1.25 mmol, respectively. Figure 2 exhibits the plot of H2
production rate vs. diboronic acid concentration in logarithmic
scale. The slope of 0.92 indicates that the acid-catalyzed
hydrolysis is also first-order with respect to the concentration of
diboronic acid. Finally, to obtain the activation energy (Ea) of
the H2 production, diboronic acid (0.5 M) was hydrolyzed in the
presence of 0.5 M sulfuric acid at various temperatures (from
303 K to 333 K). Figure 3 exhibits the plot of time vs. volume of
H2 generated during diboronic acid hydrolysis at various
temperatures. The values of the rate constant k at different
temperatures were calculated from the slope of the linear part
of each plot for the determination of the activation energy,
yielding the Ea value of 15.75 kJ/mol, based on the Arrhenius
equation. HCl was also found to catalyze B2(OH)4 hydrolysis as
well as H2SO4 with quantitative H2 formation.
The study started with hydrogen evolution upon hydrolysis of
diboronic acid (1.0 mmol) in the presence of 0.05 mol/L of
°
H2SO4 at 30 C and, in this way, H2 was obtained in 92% yield in
7 min. Then, it was found that Na2SO4 did not work, which
indicates that the catalytic efficiency of H2SO4 is attributed to
the protons (aq. H3O+). This acid-catalyzed diboronic acid
hydrolysis has been kinetically evaluated by varying the
concentrations in catalyst and diboronic acid and studying the
temperature effect. H2 evolution in this reaction has been
carried out under various acid concentrations: 0.05, 0.1, 0.2, 0.3,
0.4 and 0.5 M (mol/L), while the initial diboronic acid concen-
tration was kept constant at 0.5 M. Figure 1 shows the plots of
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
Base-catalyzed H2 evolution
In a preliminary experiment, the H2 evolution reaction has been
initially conducted by using 1 mmol of B2(OH)4 in the presence
of various amounts of Na2CO3 (from 0.2 mmol to 1.2 mmol) in
°
water (2 mL) at 30 C, and 1 mol H2 per mol B2(OH)4 was
produced (Figure 4a). The slope of the logarithmic plot of H2
generation vs. concentration of Na2CO3 is 0.86, indicating that
H2 evolution is first order in catalyst concentration. Above
1 mmol Na2CO3, the catalytic efficiency of H2 evolution no
longer increased due to the saturation of the catalyst. Na2SO4
Figure 1. Time plots of the catalytic evolution of H2 as a function of the
H2SO4 concentration. Inset image: plots of the rates of H2 generation vs. the
concentration of H2SO4, both on natural logarithmic scales.
Figure 2. Plots of the volume of hydrogen generated vs. time for the H2
evolution at various amount of B2(OH)4 (both on natural logarithmic scales).
Figure 3. Plots of the hydrogen volume vs. time for evolution of H2 catalyzed
at various temperatures (both on natural logarithmic scales).
Eur. J. Inorg. Chem. 2021, 1–7
www.eurjic.org
2
© 2021 Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/ejic.202100093
1
2
3
4
5
6
7
8
9
Figure 5. (a) Acid- and (b) base-catalyzed H2 evolution in H2O (black) or D2O
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
(red).
evolution, respectively, strongly suggesting that the OÀ H bond
of H2O is cleaved in the rate-determining reaction step in both
acid and base-catalyzed H2 evolution.[15]
H2 generated from the hydrolysis of B2(OH)4 reaction is not
only utilized for hydrogen storage, but also for in situ tandem
reactions, and for mechanistic study of the B2(OH)4 hydrolysis
reaction. For further confirming hydrogen evolution from the
diboronic acid hydrolysis reaction catalyzed by the acid catalyst,
the tandem reaction for the hydrogenation diphenylacetylene,
norbornene and 1,1-diphenylethylene with H2 produced from
diboronic acid hydrolysis catalyzed by sulfuric acid, the reaction
Figure 4. Comparison of H2 evolution catalyzed by (a) various amounts of
Na2CO3; (b) 1 mmol of different bases. (c) Time plots of the catalytic H2
evolution by 1 mmol Na2CO3 in various concentrations of B2(OH)4. (d) Plots of
the hydrogen volume vs. time for catalyzed H2 evolution at various
temperatures by Na2CO3; inset image: kinetic data obtained from the
Arrhenius plots.
°
does not work for H2 evolution, which shows that the catalytic
efficiency of Na2CO3 is attributed to CO32À . For comparison,
NH3BH3, NaBH4, B2Pin2 and B(OH)3 have been tested for base-
catalyzed H2 evolution under the same conditions, and neither
of these boron compounds works. Then, H2 evolution from
B2(OH)4 hydrolysis was carried out in the presence of 1 mmol of
various bases (Figure 4b), and it was found that Et3N, NaOH,
Na2CO3, CsOH, Cs2CO3 and KOH are very efficient for H2
evolution. The acidic bicarbonate salts KHCO3 and NaHCO3 are
less efficient than their corresponding carbonates K2CO3 and
Na2CO3, respectively. Na2HPO4 and NaH2PO4 are little efficient
for this H2 evolution reaction, indicating that the nature of the
alkali metal cation does not significantly influence the reaction.
These experiments are thus strongly in favor of OHÀ as the
active catalytic species for H2 evolution and, in the case of non-
hydroxide base, OHÀ is provided from water upon reaction with
carbonate. Then, the influence of the concentration of B2(OH)4
on H2 evolution in the presence of 1 mmol of Na2CO3 has been
was carried out in a sealed two-chamber system at 30 C for
12 h (Scheme S1), and all the reactions of diphenylacetylene,
norbornene and 1,1-diphenylethene hydrogenation provided
99% yield of the desired products, confirming H2 evolution
from acid-catalyzed diboronic acid hydrolysis. In addition, the
formation of B(OH)3 was confirmed by ESI mass spectrometry
(Figure S1), 1H (Figure S2) and 11B NMR (Figure S3) and XRD
(Figure S4). Similarly, the tandem reactions for hydrogenation of
norbornene and 1,1-diphenylethene with H2 generated from
B2(OH)4 hydrolysis catalyzed by Na2CO3 are represented in
Scheme S2. Both hydrogenations of norbornene and 1,1-
diphenylethene provided 99% yield of the desired products,
confirming the stoichiometric formation of H2 upon base-
catalyzed sealed two-chamber system (Figure 6), D2 was gen-
erated from acid-catalyzed B2(OH)4 hydrolysis with D2O, the
reaction being catalyzed diboronic acid hydrolysis. Moreover,
the mass spectrum (Figure S5) also confirmed the formation of
the reaction product, B(OH)3. In a by H2SO4 in the left chamber.
This D2 was utilized for the in-situ hydrogenation of norbornene
catalyzed by commercial Pd/C in the right chamber. Then, the
desired product 2f was obtained in 99% yield (Eq. 2), confirm-
ing that both H atoms of hydrogen are provided from water. In
parallel, D2 was also generated from base-catalyzed B2(OH)4
hydrolysis with D2O, the reaction being catalyzed by Na2CO3 in
the left chamber (Figure 7). This D2 was utilized for the in-situ
hydrogenation of norbornene catalyzed by Pd/C in the right
chamber. Then, the desired product 2g was obtained in 99%
yield (Eq. 3), also confirming that both H atoms of hydrogen are
provided from water. For the hydrogenation of 1,1-diphenyle-
thene (1c) with D2, the methyl group was 49% deuterated,
whereas the benzylic position was only 51% deuterated, which
corresponds to a total incorporation of 1.98 D, close to the
expected 2 D. (Eq. 4). The uneven distribution is due to the
°
investigated at 30 C (Figure 4c).
The slope of the logarithmic plot of H2 generation vs.
concentration of B2(OH)4 was found to be 1.02, showing that H2
evolution is first order in B2(OH)4 concentration. The efficiency
of H2 evolution at different reaction temperatures from 303 to
318 K is shown in Figure 4d. Based on the Arrhenius equation,
the activation energy (Ea) value is 46.4 kJ/mol for Na2CO3.
Kinetic and mechanistic study
The isotopic experiment using D2O instead of H2O has been
carried out for acid or base-catalyzed B2(OH)4 hydrolysis, and
the kinetic results are shown in Figure 5, showing that the
primary KIEs are 5.47 and 5.48 for acid and base-catalyzed H2
Eur. J. Inorg. Chem. 2021, 1–7
www.eurjic.org
3
© 2021 Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/ejic.202100093
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
Figure 8. Proposed mechanism for the acid-catalyzed hydrolysis of B2(OH)4.
Figure 6. Tandem reaction for hydrogenation with D2 generated from
B2(OH)4 hydrolysis using D2O catalyzed by H2SO4.
Figure 9. Proposed mechanism for the base-catalyzed hydrolysis of B2(OH)4.
For the base-catalyzed hydrolysis of B2(OH)4 reaction (Fig-
ure 9), the catalytic cycle starts with the formation of the
intermediate I by attack of OHÀ onto B2(OH)4. The intermediate
II is then produced by protonation of the anion I by water and
release of B(OH)3. Subsequently, intermediate III, obtained by
hydrolysis of II, decomposes to B(OH)3 and H2. Reductive
elimination of H2 from the BÀ O sites of III involves an important
structural reorganization that is taken into account by the
observed large primary KIE value.
Figure 7. Tandem reaction for hydrogenation in which D2 is generated from
B2(OH)4 hydrolysis with D2O catalyzed by Na2CO3.
Conclusion
facile H or D atom migration in the semi-hydrogenated radical
species[16] between the benzylic and homobenzylic positions
due to the preferred benzylic radical stabilization.
In summary, metal-free acid- or base-catalyzed H2 evolution is
reported to proceed upon hydrolysis of B2(OH)4, in which both
H atoms are obtained from water. B2(OH)4 is a frequently used
borylation reagent and also sometimes in hydrogenation, thus
the present findings are useful. Other boron compounds, such
as NH3BH3, NaBH4, B2Pin2 and B(OH)3, do not work for base-
catalyzed H2 evolution in the absence of transition-metal
nanoparticles, and in particular attempts to catalyze H2
evolution upon base catalysis from all these reagents failed.
The large primary KIEs disclosed, kH/kD =5.47 resp. kH/kD =
5.48, for acid and base-catalyzed H2 evolution from B2(OH)4,
respectively, with D2O, confirmed water OÀ H bond cleavage as
the rate- determining step for both reactions, and thus
mechanisms are proposed (Figure 8 and Figure 9). The tandem
reactions with D2O that involves B2(OH)4 hydrolysis, norbornene
A mechanistic proposal of acid-catalyzed hydrolysis of
B2(OH)4 reaction is shown in Figure 8. Initially, the intermediate
A is formed by the interaction of H3O+ with B2(OH)4. Although
oxidative addition of the BÀ B bond of diboron to d8 metal is
well known,[17] its protonation is less so. Subsequently, it gives
intermediate B by capturing one H atom from H2O. Then, the
intermediate C is afforded by the interaction of B with H3O+.
Next, C provides the intermediate D by capturing another H
atom from water releasing H2. Finally, D releases a molecule of
B(OH)3, which leads to completion of the catalytic cycle. In this
mechanism, the formation of H2 from C results from consid-
erable structural reorganization upon σ-bond metathesis,[18] for
which the large KIE value is taken into account.
Eur. J. Inorg. Chem. 2021, 1–7
www.eurjic.org
4
© 2021 Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/ejic.202100093
and 1,1-diphenylethene hydrogenation have confirmed the
province, China (T2020004), Chinese Scientific Council (PhD grant
to QZ), Université de Bordeaux and Centre National de la
Recherche Scientifique (CNRS) is gratefully acknowledged.
1
2
3
4
5
6
7
8
9
formation of D2. Note that these reactions in D2O also provide
easy and useful syntheses of D2. Based on the Arrhenius
equation, the activation energy Ea is 15.75 kJ/mol and 46.4 kJ/
mol for H2SO4 and Na2CO3, respectively.
In sum, this system has the potential to achieve metal-free Conflict of Interest
production and utilization of hydrogen, in spite of the fact that
only one H2 molecule is provided for each B2(OH)4 molecule. A
serious drawback is the difficulty of reconverting diboronic acid
from B(OH)3, but this problem also is the same for the other
hydride-rich boron derivatives such NH3BH3 and NaBH4. Recent
impressive progress has been accomplished along this line,
however,[19] and catalyzed B2(OH)4 hydrolysis is therefore
becoming an excellent method to conveniently and stoichio-
metrically generate H2 at the laboratory scale.
The authors declare no conflict of interest.
Keywords: Acid catalysis · Base catalysis · Boron · Hydrogen
evolution · Reaction mechanisms
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
[1] Z. G. Huang, S. N. Wang, R. D. Dewhurst, N. V. Ignat’ev, M. Finze, H.
Braunschweig, Angew. Chem. Int. Ed. 2020, 59, 8800–8816.
[2] a) A. Staubitz, A. P. Robertson, I. Manners, Chem. Rev. 2010, 110, 4079–
4124; b) T. He, P. Pachfule, H. Wu, Q. Xu, P. Chen, Nat. Rev. Mater. 2016,
1, 16059; c) C. Wang, D. Astruc, Chem. Soc. Rev. 2021, https://doi.org/
10.1039/D0CS00515 K; d) J. Zhou, Y. Huang, J. Shen, X. Liu, Catal. Lett.
2021, https://doi.org/10.1007/s10562-021-03547-2.
[3] a) Q.-L. Zhu, Q. Xu, Energy Environ. Sci. 2015, 8, 478–512; b) W.-W. Zhan,
Q.-L. Zhu, Q. Xu, ACS Catal. 2016, 6, 6892–6905; c) B. J. Zhu, R. Q. Zou, Q.
Xu, Adv. Energy Mater. 2018, 8, 1801193; d) J. Shen, W. Chen, G. Lv, Z.
Yang, J. Yan, X. Liu, Z. Dai, Int. J. Hydrogen Energy 2021. 46, 796–805;
e) C. Wang, J. Tuninetti, Z. Wang, C. Zhang, R. Ciganda, L. Salmon, S.
Moya, J. Ruiz, D. Astruc, J. Am. Chem. Soc. 2017, 139, 11610–11615; f) F.
Fu, C. Wang, Q. Wang, A. M. Martinez-Villacorta, A. Escobar, H. Chong, X.
Wang, S. Moya, L. Salmon, E. Fouquet, J. Ruiz, D. Astruc, J. Am. Chem.
Soc. 2018, 140, 10034–10042; g) Q. Wang, F. Fu, S. Yang, M. M. Moro, M.
de los Angeles Ramirez, S. Moya, L. Salmon, J. Ruiz, D. Astruc, ACS Catal.
2019, 9, 1110–1119; h) C. Wang, Q. Wang, F. Fu, D. Astruc, Acc. Chem.
Res. 2020, 53, 2483–2493; i) Q. Yao, K. Yang, X. Hong, X. Chen, Z.-H. Lu,
Catal. Sci. Technol. 2018, 8, 870–877; j) K. Wang, Q. Yao, S. Qing, Z.-H. Lu,
J. Mater. Chem. A 2019,7, 9903–9911; k) Q. Yao, Y. Ding, Z.-H. Lu, Inorg.
Chem. Front. 2020, 7, 3837–3874.
Experimental Section
Chemicals and reagents. All commercial materials were used
without further purification, unless indicated. The deionized water
was prepared in the laboratory. B2(OH)4, Et3N, NaOH, Cs2CO3, K2CO3,
CsOH.H2O, KOH, Na3PO4, Na2CO3, NaHCO3, KHCO3, Na2HPO4,
NaH2PO4, BH3NH3, NaBH4, D2O, CD3OD, Pd/C, B2Pin2 and B(OH)3 were
purchased from Aladdin Reagent Co., Ltd. (Shanghai, China, http://
www.aladdin-e. com/).
Acid-catalyzed evolution of H2 upon reaction between B2(OH)4
and H2O. Generally, the evolution of H2 upon reaction between
°
B2(OH)4 and H2O was conducted in water at 30 C. In a round-
bottom 10-mL flask, 1.0 mmol of B2(OH)4 was added. A solution of
H2SO4 (0.5 mol/L, 2 mL) is injected into this flask, and timing started.
The flask was fitted with a gas outlet, and a side arm was sealed
with a tight-fitting septum cap. The flask was connected via the gas
outlet to a water-filled gas burette. Gas evolution immediately
began, and the amount of gas evolved was determined periodically
[4] D. Wang, D. Astruc, Chem. Rev. 2015, 115, 6621–6686.
[5] a) T. Wartik, E. F. Apple, J. Am. Chem. Soc. 1955, 77, 6400; b) R. A. Baber,
N. C. Norman, A. G. Open, J. Rossi, New J. Chem. 2003, 27, 773–775;
c) E. C. Neeve, S. J. Geier, I. Mkhalid, S. A. Westcott, T. B. Marder, Chem.
Rev. 2016, 116, 9091–9161.
[6] a) D. S. Matteson, Tetrahedron. 1989, 45, 1859–1885; b) T. Ishiyama, M.
Murata, N. Miyaura, J. Org. Chem. 1995, 60, 7508–7510; c) V. J. Olsson, S.
Sebelius, N. Selander, K. J. Szabo, J. Am. Chem. Soc. 2006, 128, 4588–
4589.
by measuring the displacement of water in the burette.
A
quantitative conversion of B2(OH)4 produced 1.0 equivalents of H2,
and occupied ca. 22.4 mL at atmospheric pressure. Prior to the
reactions, the volumes were measured at atmospheric pressure and
corrected for water vapor pressure at room temperature.
[7] a) L. T. Pilarski, K. J. Szabo, Angew. Chem. Int. Ed. 2011, 50, 8320–8332;
b) A. Zernickel, W. Du, S. A. Ghorpade, D. N. Sawant, A. A. Makki, N.
Sekar, J. Eppinger, J. Org. Chem. 2018, 83, 1842–1851.
Base-catalyzed evolution of H2 upon reaction between B2(OH)4
and H2O. The reactions were conducted as above, except that the
H2SO4 solution was replaced by NaOH (1.0 mmol, 2 mL).
[8] a) V. Gurram, H. K. Akula, R. Garlapati, N. Pottabathini, M. M. Lakshman,
Adv. Synth. Catal. 2015, 357, 451–462; b) D. P. Ojha, K. Gadde, K. R.
Prabhu, Org. Lett. 2016, 18, 5062–5065; c) S. P. Cummings, T. N. Le, G. E.
Fernandez, L. G. Quiambao, B. J. Stokes, J. Am. Chem. Soc. 2016, 138,
6107–6110; d) M. Flinker, H. Yin, R. W. Juhl, E. Z. Eikeland, J. Overgaard,
D. U. Nielsen, T. Skrydstrup, Angew. Chem. Int. Ed. 2017, 56, 15910–
15915; e) Q. Q. Xuan, Q. L. Song, Org. Lett. 2016, 18, 4250–4253; f) X.
Han, J. Hu, C. Chen, Y. Yuan, Z. Shi, Chem. Commun. 2019, 55, 6922–
6925; g) N. N. Shaikh, RSC Adv. 2019, 9, 28199–28206; h) N. N. Shaikh,
M. A. Aziz, A. N. Kalanthoden, A. Helal, A. S. Hakeem, M. Bououdina,
Catal. Sci. Technol. 2018, 8, 4709–4717; i) K. A. Korvinson, H. K. Akula,
C. T. Malinchak, D. Sebastian, W. Wei, T. A. Khandaker, M. R. Andrzejew-
ska, B. Zajc, M. K. Lakshman, Adv. Synth. Catal. 2020, 362, 166–176;
j) A. M. Gates, W. L. Santos, Synthesis. 2019, 51, 4619–4624; k) Y. Wei, C.
Zhao, Q. Xuan, Q. Song, Org. Chem. Front. 2017, 4, 2291–2295; l) D. Pi, H.
Zhou, Y. Zhou, Q. Liu, R. He, G. Shen, Y. Uozumi, Tetrahedron. 2018, 74,
2121–2129.
The hydrogenation of diphenylacetylene, norbornene and 1,1-
diphenylethylene. The tandem reaction was carried out in the
sealed two-chamber system. The left tube was used for hydrogen
generation, and the right one was used for hydrogenation with H2
generated in the left tube. The generated hydrogen in the left tube
transported to the hydrogenation reaction into the right tube
through the connecting glass tube.
Acknowledgements
Financial support from the National Natural Science Foundation
of China (21805166), the 111 Project (D20015), the Engineering
Research Center of Eco-environment in Three Gorges Reservoir
Region, Ministry of Education, China Three Gorges University
(KF2019-05) and the outstanding young and middle-aged science
and technology innovation teams, Ministry of Education, Hubei
[9] S. K. Pedersen, H. G. Gudmundsson, D. U. Nielsen, B. S. Donslund,
H. C. D. Hammershøj, K. Daasbjerg, T. Skrydstrup, Nat. Catal. 2020, 3,
843–850.
[10] W. F. Chen, J. L. Shen, Y. P. Huang, X. Liu, D. Astruc, ACS Sustainable
Chem. Eng. 2020, 8, 7513–7522.
[11] a) Y. T. Xia, X. T. Sun, L. Zhang, K. Luo, L. Wu, Chem. Eur. J. 2016, 22,
17151–17155; b) Q. Xuan, C. Zhao, Q. Song, Org. Biomol. Chem. 2017,
Eur. J. Inorg. Chem. 2021, 1–7
www.eurjic.org
5
© 2021 Wiley-VCH GmbH
��
These are not the final page numbers!

Full Papers
doi.org/10.1002/ejic.202100093
15, 5140–5144; c) Y. Huang, K. Zheng, X. Liu, X. Meng, D. Astruc, Inorg.
Chem. Front. 2020, 7, 939–945; d) D. Chen, Y. Zhou, H. Zhou, S. Liu, Q.
Liu, K. Zhang, Y. Uozumi, Synlett. 2018, 29, 1765–1768.
[18] D. Astruc, Organometallic Chemistry and Catalysis, Springer, Berlin, 2007,
Chapter 3.
[19] Y. Zhu, L. Ouyang, H. Zhong, J. Liu, H. Wang, H. Shao, Z. Huang, M. Zhu,
1
2
3
[12] T. Wartik, E. F. Apple, J. Am. Chem. Soc. 1958, 80, 6155–6158.
[13] H. I. Schlesinger, H. C. Brown, A. E. Finholt, J. R. Gilbreath, H. R. Hoekstra,
E. K. Hyde, J. Am. Chem. Soc. 1953, 75, 215–219.
Angew. Chem. Int. Ed. 2020, 59, 8623–8629.
4
[14] S. Liu, Y. Zhou, Y. Sui, H. Liu, H. Zhou, Org. Chem. Front. 2017, 4, 2175–
5
6
7
8
2178.
[15] M. Chandra, Q. Xu, J. Power Sources. 2006, 159, 855–860.
[16] P. Michaud, D. Astruc, Angew. Chem. Int. Ed. Engl. 1982, 21, 918–919.
[17] H. E. Burks, S. Liu, J. P. Morken, J. Am. Chem. Soc. 2007, 129, 8766–8773.
Manuscript received: February 4, 2021
Revised manuscript received: March 1, 2021
Accepted manuscript online: March 2, 2021
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
Eur. J. Inorg. Chem. 2021, 1–7
www.eurjic.org
6
© 2021 Wiley-VCH GmbH
��
These are not the final page numbers!

FULL PAPERS
1
2
3
4
5
6
7
8
9
Metal-free H2 or D2 evolution is
obtained in a few minutes from acid-
or base-catalyzed hydrolysis of
diboronic acid, respectively, under
ambient conditions and is coupled to
hydrogenation reactions. Kinetic
studies allow proposing mechanisms
by considering primary kinetic
isotope effects observed for both
acid- and based-catalyzed reactions
with D2O.
Y. Wang, J. Shen, Y. Huang, Prof. Dr. X.
Liu*, Q. Zhao, Prof. Dr. D. Astruc*
1 – 7
Acid- and Base-Catalyzed Hydrolytic
Hydrogen Evolution from Diboronic
Acid
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