Novel aluminium compounds derived from Schiff bases: Synthesis, characterization and catalytic performance in hydroboration

Article abstract of DOI:10.1002/aoc.4637

Seven novel aluminium complexes supported by Schiff base ligands derived from o-diaminobenzene or o-aminothiophenol were synthesized and characterized. The reactions of AlMe₃ with L¹ (N,N′-bis(benzylidine)-o-phenylenediamine) and L

Full text of DOI:10.1002/aoc.4637

Received: 11 July 2018
DOI: 10.1002/aoc.4637
Revised: 17 September 2018
Accepted: 18 September 2018
F U L L P A P E R
Novel aluminium compounds derived from Schiff bases:
Synthesis, characterization and catalytic performance in
hydroboration
Da Jin1 | Xiaoli Ma1 | Yashuai Liu1 | Jiong Peng1 | Zhi Yang1,2
1 School of Chemistry and Chemical
Seven novel aluminium complexes supported by Schiff base ligands derived from
o‐diaminobenzene or o‐aminothiophenol were synthesized and characterized.
The reactions of AlMe3 with L1 (N,N′‐bis(benzylidine)‐o‐phenylenediamine)
and L2 (N,N′‐bis(2‐thienylmethylene)‐o‐phenylenediamine) gave the complexes
L1AlMe3 (1) and L2AlMe2 (2), respectively, which involved two types of reaction
mechanisms: one was proton transfer and ring closure, and the other was alkyl
transfer. Complexes L3AlMe2 (HL3 = 4‐chlorobenzylidene‐o‐aminothiophenol)
(3), L4AlMe2 (HL4 = 2‐thiophenecarboxaldehyde‐o‐aminothiophenol) (4),
Engineering, Beijing Institute of
Technology, Beijing 100081, China
2 State Key Laboratory of Elemento‐
organic Chemistry, Nankai University,
Tianjin 300071, China
Correspondence
Xiaoli Ma and Zhi Yang, School of
Chemistry and Chemical Engineering,
Beijing Institute of Technology, Beijing
100081 China.
L3AlH(NMe3) (5), L4AlH(NMe3) (6) and L5AlH(NMe3) (HL5
=
4‐
Email: maxiaoli@bit.edu.cn; zhiyang@bit.
edu.cn
methylbenzylidene‐o‐aminothiophenol) (7) were prepared by reacting HL3–5
with equimolar AlMe3 or H3Al⋅NMe3, respectively. Compounds 3–7 feature an
organic–inorganic hybrid containing CNAlSC five‐membered ring. All complexes
Funding information
National Nature Science Foundation of
China, Grant/Award Numbers: 21872005
and 21671018
1
were characterized using H NMR and 13C NMR spectroscopy, X‐ray crystal
structure analysis and elemental analysis. The efficient catalytic performances
of 1–7 for the hydroboration of carbonyl groups were investigated, with com-
pound 4 exhibiting the highest catalytic activity among all the complexes.
KEYWORDS
aluminium compounds, catalytic, hydroboration, ring closure, Schiff bases
1 | INTRODUCTION
hydride can be applied to facilitate hydroboration in high
yield.[11] Although the hydrogenation of aldehydes and
Organoboranes are important synthetic intermediates,
which are widely used in scientific research and are easily
obtained from hydroboration of carbonyl groups.[1] Dur-
ing past decades, various transition metal complexes, such
as those of Ni,[2] Ru,[3] Ti[4] and Cu,[5] have been utilized
as catalysts for the hydroboration of carbonyl compounds.
Compared to those transition metal catalysts, main group
metal catalysts are cheap, widespread and less toxic.[6]
Hydroboration involving main group metal catalysts
based on alkali metals,[7] magnesium,[8] group 14 metals[9]
and aluminium[10] has been investigated widely. Our
group was the first one to demonstrate that aluminium
ketones with aluminium hydroxide catalysts has been
reported,10c,e,11 the reaction using an aluminium species
has yet to be realized. We postulated that, with the correct
aluminium complex design, increased Lewis acidity and
reduced steric hindrance, the conversion of hydroboration
with aldehydes and ketones would be improved. All these
above considerations prompted us to continue to research
aluminium compounds.
Furthermore, ligands play a synergistic role in the
activation of chemical bonds. Quite a few complexes with
Schiff base ligands have been synthesized.[12] Schiff base
ligands bearing diaminobenzene usually have O‐donor
Appl Organometal Chem. 2019;e4637.
wileyonlinelibrary.com/journal/aoc
© 2019 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4637

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JIN ET AL.
(such as N,N′‐bis(salicylidene)diaminobenzene) to lead to
[O–N–N–O] chelation, which can stabilize a metal center
to form the expected well‐defined catalysts.[13] Neverthe-
less, without the modified functional group (─OH), it is
not well studied for main group metals except some tran-
sition metals.[14] Moreover, metal complexes containing
N and S are attracting increasing attention because of
their chemical and, especially, their promising biological
properties,[15] and both atoms play a vital role in the coor-
dination of metal complexes.[16] Since Jancik et al. first
reported the synthesis of species containing Al─SH units
in 2003,[17] a mushrooming number of aluminium com-
pounds with the Al─S─C core have been studied.[18]
However, few examples of compounds containing the
S─Al─N moiety in a ring have been reported.[19]
Herein, we report the synthesis and characterization of
seven novel aluminium compounds bearing Schiff bases
derived from o‐diaminobenzene or o‐aminothiophenol.
We found alkyl transfer occurred when AlMe3 reacted
with N,N′‐bis(2‐thienylmethylene)‐o‐phenylenediamine
(L2). In addition, when AlMe3 reacted with N,N′‐
bis(benzylidine)‐o‐phenylenediamine (L1), an unexpected
process occurred which involved proton transfer and ring
closure. We also synthesized five aluminium compounds
forming the rare S─Al─N modified ring through the elim-
ination of hydrogen from ligands. Finally, we investigated
the application of all compounds in catalytic
hydroboration of selected aldehydes and ketones.
SCHEME 2 Plausible mechanism of complex 1 synthesis
Although ligands L1 and L2 are similar, the reaction
mechanisms are quite different. In the formation of com-
pound 2, a methyl group was migrated from AlMe3 onto
the ligand backbone, resulting in formal insertion of
the C═N bond on the ligand into an Al─C bond.
Compounds 3–7 were prepared from reactions of HL3
(4‐chlorobenzylidene‐o‐aminothiophenol),
HL4
(2‐
thiophenecarboxaldehyde‐o‐aminothiophenol) and HL5
(4‐methylbenzylidene‐o‐aminothiophenol) with equiva-
lent amount of AlMe3 or H3Al⋅NMe3 in toluene at 0°C
(Scheme 3).
Compounds 1–7 were characterized from their 1H
NMR and 13C NMR spectra in CDCl3 solution as well as
1
using elemental analysis. In the H NMR spectrum of 1,
there was an absence of the N═CH resonance
(9.30 ppm) of ligand L1.[20] The resonances at 5.18
and −1.08 ppm revealed the existence of NCH2 and three
equivalent Me groups of AlMe3. In the 1H NMR spectrum
of 2, the singlet peak (8.74 ppm), the quartet peak (4.8,
4.78, 4.77 and 4.75 ppm) integrated with 1:3:3:1 ratio
and the doublet peak (1.68 and 1.67 ppm) integrated with
1:1 ratio could be assigned to N═CH, NCH and CHCH3,
respectively. In addition, there were resonances for the
AlCH3 groups in the high‐field region (−0.63 and
−0.72 ppm), which indicated the two Me groups were
not in the same chemical environment. Both 13C NMR
2 | RESULTS AND DISCUSSION
2.1 | Synthesis and characterization
Compounds 1 and 2 were prepared from reactions of L1
and L2, respectively, with equimolar AlMe3 in toluene at
0°C (Scheme 1). In the formation of compound 1, AlMe3
as an organic electrophile causes proton transfer. The
proposed mechanism for the synthesis of compound 1
involved ring closure in a concerted manner (Scheme 2).
1
spectra were consistent with the H NMR spectra, show-
ing characteristic signals for N═CH (153.15 ppm for 1
SCHEME 1 Preparation of compounds 1 and 2
SCHEME 3 Preparation of compounds 3–7

JIN ET AL.
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and 150.93 ppm for 2) of the ligands and AlMe
(−14.22 ppm for 1 and −8.29, −9.11 ppm for 2) in the
1
high‐field region. In the H NMR spectra of compounds
3–7, the disappearance of SH resonances (3.4 to
4.3 ppm) in the ligands[21] and the appearance of AlMe2
resonances at high–field region (−0.75 to −0.6 ppm) or
NMe3 group resonances at 2.3 ppm and CH2 resonances
at 4.46 to 4.66 ppm indicated the formation of desired
complexes.
2.2 | Crystal structures
FIGURE 2 Molecular structure of 2 in crystals. Thermal ellipsoids
are drawn at 50% level. The hydrogen atoms are omitted for clarity.
Selected bond distances (Å) and angles (°): Al(1)–N(1) 1.874(3),
Al(1)–C(1) 1.969(4), Al(1)–C(2) 1.970(4), Al(1)–N(2) 1.996(3), N(1)–
C(4) 1.460(4), N(2)–C(3) 1.296(4); N(1)–Al(1)–C(1) 114.31(15), N(1)–
Al(1)–C(2) 115.17(15), C(1)–Al(1)–C(2) 118.1(2), N(1)–Al(1)–N(2)
85.69(11), C(1)–Al(1)–N(2) 110.12(16), C(2)–Al(1)–N(2) 108.36(16)
X‐ray‐quality single crystals of 1–7 were obtained in
toluene. The X‐ray single‐crystal structures show that
compounds 1 and 3–7 belong to the monoclinic crystal
system while 2 belongs to the triclinic crystal system.
All crystals are soluble in common organic solvents,
such as toluene, dichloromethane and tetrahydrofuran.
The molecular structures (1, 2, 3 and 5) are shown in
Figures 1–4, with selected bond lengths and angles in the
captions of, while other similar structures (4, 6 and 7) are
shown in the supporting information (Figures S1–S3).
In compound 1, the aluminium center exhibits a
distorted tetrahedral geometry including a nitrogen atom
on the ligand and three carbon atoms from three methyl
groups. The bond angles around the aluminium atom
range from 102.08 (11)° to 115.79 (16)°. The bond length
of Al←N is 2.014 (2) Å, which is shorter than the corre-
sponding Al←N bond length in [AlMe3{NH(But)Ph}]
(2.067(4) Å)[22] and AlMe3(NMe3) (2.099(10) Å).[23] Mean-
while, the three bound angles of C─Al─N (108.91(12)°,
FIGURE 3 Molecular structure of
3 in crystals. Thermal
ellipsoids are drawn at 50% level. The hydrogen atoms are omitted
for clarity. Selected bond distances (Å) and angles (°): Al(1)–S(1)
2.2877(8), Al(1)–N(1) 2.0181(18), Al(1)–C(8) 1.966(2), Al(1)–C(7)
1.977(2); C(8)–Al(1)–C(7) 119.93(10), C(8)–Al(1)–N(1) 114.65(9),
C(7)–Al(1)–N(1) 104.98(8), C(8)–Al(1)–S(1) 112.10(8), C(7)–Al(1)–
S(1) 112.41(8), N(1)–Al(1)–S(1) 88.19(5)
FIGURE 1 Molecular structure of
1 in crystals. Thermal
ellipsoids are drawn at 50% level. The hydrogen atoms are omitted
for clarity. Selected bond distances (Å) and angles (°): Al(1)–C(22)
1.962(3), Al(1)–C(21) 1.980(3), Al(1)–C(23) 1.989(3), Al(1)–N(1)
2.014(2); C(22)–Al(1)–C(21) 115.79(16), C(22)–Al(1)–C(23)
109.84(14), C(21)–Al(1)–C(23) 114.77(14), C(22)–Al(1)–N(1)
108.91(12), C(21)–Al(1)–N(1) 102.08(11), C(23)–Al(1)–N(1)
104.37(11)
FIGURE 4 Molecular structure of 5 in crystals. Thermal ellipsoids
are drawn at 50% level. The hydrogen atoms are omitted for clarity.
Selected bond distances (Å) and angles (°): Al(1)–S(1) 2.2263(6),
Al(1)–N(2) 1.8194(14), Al(1)–N(1) 1.9999(15); N(2)–Al(1)–N(1)
107.96(6), N(2)–Al(1)–S(1) 93.93(5), N(1)– Al(1) –S(1) 108.46(4)

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JIN ET AL.
104.37 (11)° and 102.08 (11)°) are similar to those in
(2.0027(8) Å).[27] Each of the C–S–Al–N–C five‐
membered rings is approximately coplanar and the three
sums of the inner angles are 538.91°, 539.10° and
538.99°, respectively.
[AlMe3{NH(But)Ph}]
106.14 (16)°).
(108.5(4)°,
107.8 (2)°
and
In compound 2, L2 forms a five‐membered N–N che-
late moiety with Al. The aluminium center is described
as
a four‐coordinated distorted tetrahedron, being
2.3 | Catalytic performance
surrounded by two nitrogen atoms on the ligand and
two carbon atoms from methyl groups. The sum of the
inner angles of the C–N–Al–C–N five‐membered ring is
538.33°, which is close to that of the ideal planar ring of
540°. The Al←N coordinate bond (1.996(3) Å) is slightly
shorter than that in compound 1. The Al─N single bond
(1.874(3) Å) is significantly shorter than the Al←N coordi-
nate bond, and both are slightly longer than those in
[Cy[NC(CH2)‐2‐(C5H4N)AlMe2]2] (1.861(1) Å for Al─N
and 1.973(1) Å for Al←N),[24] respectively. The N(2)═
C(3) (1.296(4) Å) double bond is much shorter than and
distinct from the N(1)─C(4) single bond (1.460(4) Å).
The N(1)─Al─N(2) angle (85.69(11)°) is larger than that
in (DiPPDAB (Me2)) (84.40(4)°).[25]
In compounds 3 and 4, the central aluminium exhibits
a distorted tetrahedral geometry with a sulfur atom, a
nitrogen atom and two carbon atoms. The sums of the
inner angles of C–N–Al–S–C five‐membered ring are
539.04° and 531.23°, respectively. In 3, the bond lengths
of Al─S (2.2877(8) Å) and Al←N (2.0181(18) Å) are shorter
than those of Al(1)─S(2) (2.3137(7) Å) and Al(1)─N(5)
(2.1208(17) Å) in [LAl[(m‐S)(m‐pyrimidine)(CH2)2]2]
reported by our group previously.[26] In 4, the Al─S bond
length (2.2939(11) Å) is longer than that in 3, while the
Al←N bond length (2.005(3) Å) is shorter than that in 3.
In compounds 5–7, the central aluminium atom is
four‐coordinated, being surrounded by a nitrogen atom
and a sulfur atom on the ligand, one nitrogen atom
from the NMe3 group and one hydrogen atom. The
imino groups have been transformed into amido func-
tionality, forming cyclopentyl‐bearing aluminium
metallacycles. Their Al─S bond lengths (2.2263(6) Å
for 5, 2.2291(6) Å for 6 and 2.2294(4) Å for 7) are close
to each other and shorter than those in 3 and 4. Their
Al─N bond lengths (1.8194(14) Å for 5, 1.8200(12) Å
for 6 and 1.8208(10) Å for 7) are significantly shorter
than those of the Al←N coordinate bonds in 3 and 4.
Meanwhile, compared to the corresponding bond
lengths and angle in the structure of [LAl[(μ‐N)(μ‐S)]
(o‐C6H4)] (Al(1)─S(1), 2.2274(15) Å; Al(1)─N(3),
1.799(4) Å; N(3)─Al(1)─S(1), 93.52(12)°),[19] the Al─S
bond lengths are quite similar, the Al─N bond lengths
are longer and the N─Al─S angles (108.46(4)° for 5,
105.88(4)° for 6 and 108.81(3)° for 7) are more obtuse.
Their Al←NMe3 bond lengths (1.9999(15) Å for 5,
1.9906(13) Å for 6 and 1.9982(11) Å for 7) are compara-
ble to that in [(2,6‐iPr2C6H3)NC(Me)]2AlH(NMe3)]
The catalytic performance of all the complexes in
hydroboration with selected aldehydes and ketones was
evaluated. We carried out the reactions by adding catalysts
1–7 to an equimolar mixture of HBpin and carbonyl com-
pounds in C6D6. The results are presented in Table 1. We
noticed that compounds 1–7 are active catalysts for
hydroboration of benzaldehyde and the yields were
99% within 1 h at room temperature. The conversions
1
were concluded from H NMR analysis. In contrast, the
catalyst‐free hydroboration of benzaldehyde displayed lit-
tle conversion. The hydroboration of ketone with HBpin
using all compounds as catalysts at room temperature
showed slower progress than that of aldehydes. However,
on heating the reaction mixture to 60°C, the acetophenone
conversion was significantly improved for all cases, with
the highest up to 92% yield in 5 h. From Table 1, it is evi-
dent that the catalytic efficiency of 1–4 is higher than that
of 5–7. It might be that the methyl group directly attached
to aluminium as electron‐donating group improved
the catalytic efficiency. Meanwhile, the ─NMe3 group
attached to aluminium might reduce the catalytic effi-
ciency due to its steric hindrance. Moreover, we found that
4 exhibits the highest catalytic activity among the seven
complexes and the catalytic efficiency is comparable to
that of other similar complexes reported previously.10a,c
The mechanism of aluminium hydride‐catalyzed
hydroboration of carbonyl compounds (insertion/σ‐bond
metathesis type) was previously investigated by our
group[11] and others.10c,e Herein, we proposed an
insertion/σ‐bond metathesis type of mechanism
(Scheme 4). For compound 4, we proposed that Al–Me,
similar to Mg–nBu,[28] reacted with HBpin to form
hydride. And then, Al─H bond inserted into the C═O
functional group to form the corresponding aluminum
alkoxide intermediate. Finally, the reaction of the metal
alkoxide with HBpin via σ‐bond metathesis to yield the
alkoxyboronate product regenerates the aluminum
hydride catalyst for further reaction.
3 | EXPERIMENTAL
3.1 | General procedures
All manipulations were carried out under a purified
nitrogen atmosphere using Schlenk techniques or inside

JIN ET AL.
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TABLE 1 Hydroboration of aldehydes and ketones catalyzed by 1–7a
Entry
Substrate
Catalyst
Loading (mol%)
Temperature (°C)
Time (h)
Yield (%)b
a
None
0
25
1
Trace
b
1
1
25
1
99
c
1
1
1
2
25
60
1
5
99
86
d
e
2
1
25
1
99
f
2
2
1
2
25
60
1
5
99
89
g
h
3
1
25
1
99
i
j
3
3
1
2
25
60
1
5
99
88
k
4
1
25
1
99
l
4
4
1
2
25
60
1
5
99
92
m
n
5
1
25
1
99
o
p
5
5
1
2
25
60
1
5
99
85
(Continues)

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JIN ET AL.
TABLE 1 (Continued)
Entry
Substrate
Catalyst
Loading (mol%)
Temperature (°C)
Time (h)
Yield (%)b
q
6
1
25
1
99
r
s
6
6
1
2
25
60
1
5
99
82
t
7
1
25
1
99
u
v
7
7
1
2
25
60
1
5
99
76
aAll reactions carried out in benzene‐d6 using 1 equiv. of HBpin.
bConversion was determined by NMR spectroscopy on the basis of the consumption of the aldehyde/ketone, and the identity of the product was confirmed by R′
CH2OBpin or R′R″CHOBpin signal in NMR spectra.
the Analytical Instrumentation Center of the Beijing
Institute of Technology. NMR spectra were recorded with
a Bruker AM 400 spectrometer. Melting points were
measured in sealed glass tubes.
3.2 | Preparation of complexes
3.2.1 | Synthesis of L1AlMe3 (1)
AlMe3 (1 M in toluene, 1 ml, 1 mmol) was added drop by
drop to a solution of L1 (0.284 g, 1 mmol) in toluene
(10 ml) at 0°C. After the addition was completed, the
reaction mixture was allowed to warm to room tempera-
SCHEME 4 Proposed mechanism for hydroboration of carbonyl
compounds catalyzed by compound 4
ture and stirring was continued for 24 h. And then the
solution was filtered. The filtrate was concentrated to
5 ml and was stored at −20°C in a freezer for 3 days to
afford compound 1 as yellow crystals. Yield 0.20 g
(56%); m.p. 235°C decomposed. 1H NMR (400 MHz,
CDCl3, 298 K, TMS, δ, ppm): 7.45–7.11 (m, 14 H,
Ar–H), 5.18(s, 2 H, NCH2), −1.08 (s, 9 H, AlMe3). 13C
NMR (400 MHz, CDCl3, 298 K, TMS, δ, ppm): 153.15
(NCN), 142.19, 135.39, 135.05, 129.09, 128.87, 128.37,
128.32, 128.24, 128.03, 127.71, 127.32, 126.74, 126.65,
an Etelux MB 200G glovebox. All solvents were refluxed
with the appropriate drying agent and distilled prior to
use. Commercially available chemicals were purchased
from J&K chemical or VAS and used as received. L1–2
and HL3–5 were prepared as previously described in the
literature.[20,21,29] Elemental analyses were performed at

JIN ET AL.
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124.95, 121.99, 121.63, 118.99, 109.48 (C of Ar), 47.37
(CH2), −14.22 (AlMe3). Elemental analysis, calcd for
C23H25AlN2 (356.44) (%): C 77.50, H 7.07, N 7.86; found
(%): C 78.08, H 7.14, N 7.99.
analysis, calcd for C13H14AlNS2 (275.37) (%): C 56.70, H
5.12, N 5.09; found (%): C 57.21, H 5.01, N 5.36.
3.2.5 | Synthesis of L3AlH(NMe3) (5)
3.2.2 | Synthesis of L2AlMe2 (2)
Compound 5 was synthesized using the same procedure
as for 1, reacting H3Al⋅NMe3 (1 M in toluene, 1 ml,
1 mmol) with HL3 (0.248 g, 1 mmol) in toluene
(10 ml) to afford colorless crystals. Yield 0.29 g (87%);
m.p. 155–156°C. 1H NMR (400 MHz, CDCl3, 298 K,
TMS, δ, ppm): 7.29–6.17 (m, 8 H, Ar–H), 4.49 (s, 2 H,
NCH2), 2.33 (s, 9 H, NMe3). 13C NMR (400 MHz, CDCl3,
298 K, TMS, δ, ppm): 150.47, 138.37, 130.54, 128.53,
127.50, 127.14, 127.00, 124.03, 122.94, 115.04, 114.26,
109.69 (C of Ar), 47.26 (CH2), 45.80 (NMe3). Elemental
analysis, calcd for C16H20AlClN2S (334.84) (%):
C, 57.39; H, 6.02; N, 8.37; found (%): C, 58.05; H, 6.12;
N, 8.58.
Compound 2 was synthesized using the same procedure
as for 1, using AlMe3 (1 M in toluene, 1 ml, 1 mmol) with
L2 (0.296 g, 1 mmol) in toluene (10 ml) to afford black
1
crystals. Yield 0.15 g (51%); m.p. 132–134°C. H NMR
(400 MHz, CDCl3, 298 K, TMS, δ, ppm): 8.74 (s, 1 H,
NCH), 7.76–6.84 (m, 10 H, H of Ar or thiophene), 4.78
(q, J = 4 Hz, 1 H, CHCH3), 1.67(d, J = 8 Hz, 3 H,
CHCH3), −0.63 (s, 3 H, AlCH3), −0.72 (s, 3 H, AlCH3).
13C NMR (400 MHz, CDCl3, 298 K, TMS, δ, ppm):
150.93 (NCH), 150.09, 148.89, 135.69, 135.46, 134.39,
131.52, 130.23, 127.89, 125.51, 122.00, 121.90, 114.49,
111.89, 111.57 (C of Ar or thiophene), −8.29, −9.11
(AlMe2). Elemental analysis, calcd for C19H21AlN2S2
(368.49) (%): C 61.93, H 5.74, N 7.60; found (%): C 62.62,
H 5.85, N 7.86.
3.2.6 | Synthesis of L4AlH(NMe3) (6)
Compound 6 was synthesized using the same procedure
as for 1, reacting H3Al⋅NMe3 (1 M in toluene, 1 ml,
1 mmol) with HL4 (0.219 g, 1 mmol) in toluene (10 ml)
to afford colorless crystals. Yield 0.25 g (82%); m.p.
103–105°C. 1H NMR (400 MHz, CDCl3, 298 K, TMS,
δ, ppm): 7.29–6.47 (m, 7 H, H of Ar or thiophene), 4.66
(s, 2 H, NCH2), 2.29 (s, 9 H, NMe3). 13C NMR
(400 MHz, CDCl3, 298 K, TMS, δ, ppm): 150.75, 144.76,
129.32, 125.75, 125.15, 123.84, 123.14, 122.81, 115.15,
109.27 (C of Ar or thiophene), 45.06 (CH2), 44.85
(NMe3). Elemental analysis, calcd for C14H19AlN2S2
(306.43) (%): C 54.87, H 6.25, N 9.14; found (%): C 55.65,
H 6.36, N 9.44.
3.2.3 | Synthesis of L3AlMe2 (3)
Compound 3 was synthesized using the same procedure
as for 1, using AlMe3 (1 M in toluene, 1 ml, 1 mmol) with
HL3 (0.248 g, 1 mmol) in toluene (10 ml) to afford red
1
crystals. Yield 0.21 g (70%); m.p. 140–142°C. H NMR
(400 MHz, CDCl3, 298 K, TMS, δ, ppm): 8.71 (s, 1 H,
NCH), 7.71–6.95 (m, 8 H, Ar–H), −0.75 (s, 6 H, AlMe2).
13C NMR (400 MHz, CDCl3, 298 K, TMS, δ, ppm):
166.48 (NCH), 145.88, 141.26, 140.97, 133.26, 132.00,
130.61, 130.43, 129.73, 128.92, 127.96, 123.87,
119.23(C of Ar), −7.37 (AlMe2). Elemental analysis, calcd
for C15H15AlClNS (303.79) (%): C 59.31, H 4.98, N 4.61;
found (%): C 60.02, H 5.11, N 4.83.
3.2.7 | Synthesis of L5AlH(NMe3) (7)
Compound 7 was synthesized using the same procedure
as for 1, reacting H3Al⋅NMe3 (1 M in toluene, 1 ml,
1 mmol) with HL5 (0.227 g, 1 mmol) in toluene (10 ml)
to afford colorless crystals. Yield 0.26 g (83%); m.p.
3.2.4 | Synthesis of L4AlMe2 (4)
Compound 4 was synthesized using the same procedure
as for 1, reacting AlMe3 (1 M in toluene, 1 ml, 1 mmol)
with HL4 (0.219 g, 1 mmol) in toluene (10 ml) to afford
red crystals. Yield 0.18 g (65%); m.p. 132–133°C. 1H
NMR (400 MHz, CDCl3, 298 K, TMS, δ, ppm): 8.73 (s, 1
H, NCH), 7.88–6.92 (m, 8 H, H of Ar or thiophene),
−0.60 (s, 6 H, AlMe2). 13C NMR (400 MHz, CDCl3,
298 K, TMS, δ, ppm): 156.74 (NCH), 144.51, 139.84,
136.65, 136.35, 135.04, 132.14, 128.80, 128.36, 122.67,
117.78 (C of Ar or thiophene), −8.32 (AlMe2). Elemental
1
123–125°C. H NMR (400 MHz, CDCl3, 298 K, TMS, δ,
ppm): 7.28–6.25 (m, 8 H, H of Ar), 4.46 (s, 2 H, NCH2),
2.26 (s, 12 H, NMe3 and ArMe). 13C NMR (400 MHz,
CDCl3, 298 K, TMS, δ, ppm): 151.19, 136.84, 135.38,
129.18, 128.06, 127.62, 126.57, 126.03, 125.06, 123.13,
114.71, 109.36 (C of Ar), 49.22 (CH2), 45.50 (NMe3),
20.04 (ArMe). Elemental analysis, calcd for C17H23AlN2S
(314.42) (%): C 64.94, H 7.37, N 8.91; found (%): C 65.66,
H 7.29, N 9.15.

8 of 10
JIN ET AL.
the supplementary crystallographic data for compounds
1–7, respectively, and can be obtained free of charge via
www.ccdc.cam.ac.uk/deposit.
3.3 | X‐ray crystallography
The crystallographic data for compounds 1–7 were
collected using a Rigaku AFC10 Saturn 724+ (2 × 2
bin mode) diffractometer equipped with graphite‐
monochromated Mo Kα radiation (λ = 0.71073 Å).
Empirical absorption correction was applied using the
SADABS program.[30] Structures were solved by direct
methods[31] and refined by full matrix least squares on
F 2 using the SHELXL‐97 program.[32] Crystallographic
data are provided in Table 2. CCDC 1840545, 1840546,
1840547, 1840549, 1840548, 1841410 and 1841411 contain
3.4 | Hydroboration catalyzed by
complexes 1–7
Benzaldehyde (0.1 ml, 1 mmol), HBpin (0.15 ml, 1 mmol)
and C6D6 (1 ml) were loaded in a dried J‐Young tube under
nitrogen atmosphere. The mixture was placed in a sealed
TABLE 2 Crystal data and structure refinement for 1–7
Compound
1
2
3
4
5
6
7
Empirical
formula
C23H25AlN2
C27H32AlN2S2 C15H15AlClNS
C13H14AlNS2 C16H20AlClN2S C14H19AlN2S2
C17H23AlN2S
Formula
weight
356.43
475.64
303.77
275.35
333.82
306.41
314.41
Temperature
(K)
153.1500
153.1500
153.1500
153.1500
153.1500
153.1500
153.1500
Crystal system
Space group
a (Å)
Monoclinic
P21/c
Triclinic
P‐1
Monoclinic
P21/c
Monoclinic
P21/n
Monoclinic
P21/n
Monoclinic
P21/c
Monoclinic
P21/n
10.277(2)
22.465(5)
8.8469(19)
90.00
9.3370(10)
10.9234(12)
13.3951(15)
67.141(3)
75.170(3)
87.410(3)
1214.7(2)
2
9.4300(6)
7.8023(5)
20.4565(13)
90.00
9.4743(5)
7.9722(4)
18.1371(9)
90.00
11.3508(11)
10.1156(9)
15.3560(14)
90.00
11.0474(8)
9.6300(7)
18.2395(13)
90.00
11.3366(7)
10.2462(6)
15.3908(9)
90.00
b (Å)
c (Å)
α (deg)
β (deg)
γ (deg)
V (Å3)
96.993(7)
90.00
90.591(2)
90.00
93.550(1)
90.00
97.067(2)
90.00
103.748(2)
90.00
97.781(2)
90.00
2027.3(7)
4
1505.02(17)
4
1367.29(12)
4
1749.8 (3)
4
1884.8(2)
4
1771.29(18)
4
Z
ρc (g cm−3
μ (mm−1
)
1.168
1.300
1.341
1.338
1.267
1.080
1.179
)
0.108
0.274
0.436
0.430
0.383
0.319
0.228
Crystal size
(mm)
0.3 × 0.15 × 0.1 0.2 × 0.15 × 0.1 0.3 × 0.15 × 0.1 0.3 × 0.15 × 0.1 0.3 × 0.15 × 0.1 0.2 × 0.15 × 0.1 0.2 × 0.15 × 0.1
θ range (deg)
1.813–25.048
1.708–25.047
1.991–25.049
2.250–28.277
2.112–25.049
1.898–28.302
2.101–28.244
Reflections
collected
2513
3828
2459
3184
2736
3837
3865
R(int)
0.0792
3589/0
235
0.0310
4297/52
289
0.0240
2674/0
172
0.0222
3389/12
154
0.0434
3087/1
194
0.0279
4674/1
176
0.0278
4358/0
194
Data/restraints
Parameters
F (000)
760.0
506.0
632.0
576.0
704.0
648.0
672.0
R1a, wR2b
(I > 2σ(I))
0.0572, 0.1484 0.0745, 0.2186 0.0359, 0.0997 0.0690, 0.2177 0.0308, 0.0821 0.0349, 0.1187 0.0315, 0.0898
R1a, wR2b (all
0.0888, 0.1668 0.0806, 0.2265 0.0388, 0.1017 0.0718, 0.2211 0.0359, 0.0856 0.0433, 0.1292 0.0358, 0.0923
data)
aR = Σ|| F 0| − | F c||/Σ| F 0|.
2
bwR2 = [Σw( F 0 − F c2)2/Σ( F 02)]1/2
.

JIN ET AL.
9 of 10
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environmentand stirred at roomtemperatureandthe prog-
ress was followed by 1H NMR and 13C NMR spectroscopy.
Compound 1 (0.01 or 0.02 mmol) was added to a
solution of aldehyde (1 mmol) or ketone (1 mmol) with
HBpin (0.15 ml, 1 mmol) in C6D6 (1 ml) under nitrogen
atmosphere. The mixture was placed in a sealed environ-
ment and stirred at room temperature. The reaction was
terminated by exposing the mixture to air. The conversion
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Hydroboration of aldehydes and ketones catalyzed by
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4 | CONCLUSIONS
In summary, seven novel aluminium complexes sup-
ported by Schiff bases have been synthesized and fully
characterized. The possible mechanism for the synthesis
of 1 was investigated. The catalytic performances of all
complexes towards hydroboration of aldehydes and
ketones were evaluated. Compound 4 exhibits the highest
catalytic activity among the seven complexes. Moreover,
complexes 3–7 are interesting precursors for the prepara-
tion of new aluminium compounds. We are concentrat-
ing on synthesizing some novel compounds based on
these and expanding their applications.
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ACKNOWLEDGMENTS
[10] a) A. Bismuto, M. J. Cowley, S. P. Thomas, ACS Catal. 2018, 8,
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We gratefully acknowledge financial support of this work
by the National Nature Science Foundation of China
(21671018, 21872005).
ORCID
Zhi Yang https://orcid.org/0000-0002-5732-0326
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How to cite this article: Jin D, Ma X, Liu Y,
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characterization and catalytic performance in
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