Sodium organoaluminate containing bidentate pyrrolyl ligand: Synthesis, structure, and catalytic activity for the Tishchenko reaction

Article abstract of DOI:10.1016/j.jorganchem.2021.121882

An novel sodium organoaluminate containing bidentate pyrrolyl ligand [C₄H₃NH(2-CH₂NH^tBu)] was efficiently synthesized and characterized by X-ray crystallography. The molecular structure shows it is a monodimensional infinite chain structures with linear arrangements. Its basic repeat unit comprises the Al atom bonded to two deprotonated pyrrole rings and Na atom coordinated to of nitrogen atoms of –N^tBu fragment, which undergoes further to coordinates a pyrrolyl ring of an adjacent molecule in a ?²-fasion. Furthermore, this sodium organoaluminate exhibited high catalytic activities for Tishchenko reaction.

Full text of DOI:10.1016/j.jorganchem.2021.121882

Journal of Organometallic Chemistry 945 (2021) 121882
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Sodium organoaluminate containing bidentate pyrrolyl ligand:
Synthesis, structure, and catalytic activity for the Tishchenko reaction
Yu Liua, Zhiqiang Guob,∗, Yakong Wang c
a Naval Logistic Academy, Tianjin, 300450, P.R. China
b Scientific Instrument Center, Shanxi University, Taiyuan, 030006, P.R. China
c School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan, 030006, P.R. China
a r t i c l e i n f o
a b s t r a c t
An novel sodium organoaluminate containing bidentate pyrrolyl ligand [C4H3NH(2-CH2NHtBu)] was ef-
ficiently synthesized and characterized by X-ray crystallography. The molecular structure shows it is a
monodimensional infinite chain structures with linear arrangements. Its basic repeat unit comprises the
Al atom bonded to two deprotonated pyrrole rings and Na atom coordinated to of nitrogen atoms of
–NtBu fragment, which undergoes further to coordinates a pyrrolyl ring of an adjacent molecule in a
ƞ2-fasion. Furthermore, this sodium organoaluminate exhibited high catalytic activities for Tishchenko re-
action.
Article history:
Received 16 February 2021
Revised 30 April 2021
Accepted 6 May 2021
Available online 12 May 2021
Keywords:
Sodium organoaluminate
Pyrrolyl ligand
Synthesis
© 2021 Elsevier B.V. All rights reserved.
Structure
Tishchenko reaction
1. Introduction
(Me CNCH )C H N]Na(Et O)} exhibited higher catalytic activities
∞
3
2
4
3
2
and chemoselectivity under mild conditions [5]. As part of our
continuing interest in developing bimetallic compounds containing
substituted pyrrolyl ligand as catalysts, here we report the synthe-
sis and structural features of sodium organoaluminate containing
bidentate pyrrolyl ligand and their catalytic activity for Tishchenko
reaction.
The Tishchenko reaction,
a representative atomic-economic
esterification reaction, has attracted great attention and re-
mained prosperity since it was first reported by L. Claisen in
1887 [1]. Despite it has been thoroughly studied, comprehen-
sively reviewed many times, and multifarious types of cata-
lysts and methods have been developed for high catalytic activ-
ities to afford the corresponding esters [2]. But a highly selec-
tive crossed-Tishchenko reaction with the formation of a single
cross-coupled unsymmetrical ester from the four possible prod-
ucts remains challenging. Although some groups have attempted
to improve the selectivity of this transformation, for example,
Ogoshi’s group reported the nickel/N-heterocyclic carbene (NHC)-
catalyzed highly selective Tishchenko reaction between alkyl and
aromatic aldehydes, this can be considered an important mile-
stone to establishing crossed-Tishchenko reactions [3]. Connon
et al. also reported the thiolate-catalyzed, highly chemoselective
cross-Tishchenko reaction between aromatic aldehyde and another
ortho-substituted aromatic aldehyde [4]. Up to now, highly se-
lective crossed-Tishchenko reactions have been successfully per-
formed only for very special substrate combinations. Very recently,
we have reported the sodium alkyl magnesiate complex {nBuMg[2-
2. Experimental
2.1. General methods and materials
The syntheses and manipulations of air sensitive materials were
performed using the standard Schlenk techniques. Tetrahydrofu-
ran and diethyl ether were distilled from sodium-benzophenone
under inert atmosphere. Hexane and toluene is also dried using
sodium potassium alloy and distilled under inert atmosphere prior
to use. All aldehydes (purity ≥ 97%) purchased from Aladdin were
recrystallized or distilled before use. NaH (60% dispersion in min-
eral oil) was purchased from Aladdin and washed with hexane
three times in a Schlenk tube before use. The ligand [C4H3NH(2-
CH2NHtBu)] was synthesized according our previous reports [6].
1H NMR (600 MHz) and 13C NMR (151 MHz) spectra were recorded
on a BRUKER AVANCE III 600 MHz instrument in CDCl3, C6D6 and
C5D5N at 298 K. Elemental analyses were performed on a Vario
EL-III instrument.
∗
Corresponding author.
E-mail address: gzq@sxu.edu.cn (Z. Guo).
https://doi.org/10.1016/j.jorganchem.2021.121882
0022-328X/© 2021 Elsevier B.V. All rights reserved.

Y. Liu, Z. Guo and Y. Wang
Journal of Organometallic Chemistry 945 (2021) 121882
2.2. Synthesis of sodium organoaluminate complex
The solution of [C4H3NH(2-CH2NHtBu)] (0.913 g, 6.0 mmol) in
THF (20 mL) was added slowly to a suspension of NaH (0.12 g,
3.0 mmol) in THF (20 mL) at −78 °C. The reaction was warmed
to room temperature and stirred for 3 h, followed by addition
of a solution of Al(CH3)3 (3.0 mmol, 1.0 M in hexane). After the
mixture was then stirred for another 12 h at room temperature,
the solution was filtered and concentrated. The residue was re-
crystallized from a saturated THF/hexane solution to give color-
less crystals (0.698 g, 61% yield). 1H NMR (600 MHz, C6D6+C5D5N)
δ 7.47 (s, 2H, C4H3N), 6.49 (s, 2H, C4H3N), 6.19 (s, 2H, C4H3N),
3.75 (d, J = 8.5 Hz, 4H, CH2NBut), 0.93(s, 3H, Al(CH3)2) 0.79
(s, 18H, CH2NBut), 0.14 (s, 3H, Al(CH3)2). 13C NMR (151 MHz,
C6D6+C5D5N) δ 138.18 (C4H3N), 127.29 (C4H3N), 109.48 (C4H3N),
108.73 (C4H3N), 50.56 (C(CH3)3), 41.09 (CH2NBut), 29.03 (Al(CH3)2),
28.58 (C(CH3)3). Anal. Calcd for C20H36AlN4Na: C, 62.80; H, 9.49; N,
14.65. Found: C, 62.71; H, 9.53; N, 14.56.
Scheme 1. Synthetic routes to sodium organoaluminate complex.
responding pyrrole ring protons showed resonance signals at ex-
pected regions, and the NMR spectra also supported the presence
of the carbon atom in complex. These results are consistent with
the structure determined from X-ray analysis.
Single crystals of sodium organoaluminate suitable for X-ray
quality was grown from a concentrated solution of THF and hex-
ane at room temperature. As illustrated in Fig. 1. Single crys-
tal X-ray diffraction showed that it is a monodimensional infi-
nite chain structures with linear arrangements. Details of the crys-
tallographic data, the selected bond lengths and bond angles are
provided in supporting information. In the solid state, its basic
repeat unit comprises the Al atom bonded to two deprotonated
pyrrole rings and Na atom coordinated to of nitrogen atoms of –
NtBu fragment, which undergoes further to coordinates a pyrrolyl
ring of an adjacent molecule in a ƞ2-fasion. The aluminum atom
completes its tetracoordinated environment with nitrogen atoms of
two pyrrolyl ligand and two methyl groups. The bond distance of
2.3. General procedure for Tishchenko reaction with sodium
organoaluminate complex as catalyst
Benzaldehyde (102 uL, 10 mmol) was added to a 25 mL Schlenk
tube charged with sodium organoaluminate (0.076 g, 0.2 mmol)
under nitrogen. After the reaction mixture was stirred for 3 h at
50 °C, it was quenched with HCl solution (0.5 M), and was ex-
tracted three times with ethyl acetate. The combined organic lay-
ers were dried over Na2SO4. Removal of all volatiles in vacuo,
the crude product was purified by column chromatography on sil-
ica gel (Hexane/EtOAc: 10/1–5/1). All carbonates were identified
through comparisons with the NMR data reported in the literatures
[2o].
˚
˚
Al-N1 1.9174(12) A and Al-N3 1.8996(12) A, respectively, which are
similar to the values reported for other pyrrolyl aluminum com-
pound [6a]. The distances between the sodium atom and two car-
bon atoms of the adjacent pyrrole ring were found to be 2.9135(15)
˚
and 2.9281(16) A, respectively, indicates it displays a long-range
interaction. The bond lengths of Na-N2 and Na-N4 are 2.4560(12)
˚
and 2.4328(12) A, which are comparable with that of the reported
2.4. General procedures for the selective crossed Tishchenko reaction
with sodium organoaluminate complex as catalyst
[7].
3.2. The Tishchenko reaction catalyzed by sodium organoaluminate
complex
To
a 25 mL Schlenk tube with a magnetic stirring bar,
was successively added benzaldehyde (102 uL, 10 mmol), o-
bromobenzaldehyde (117 uL, 10 mmol) and sodium organoalumi-
nate (0.076 g, 0.2 mmol). The mixture was stirred at 50 °C for
3 h. After the reaction mixture was stirred for 3 h at 50 °C, it
was quenched with HCl solution (0.5 M), and was extracted three
times with ethyl acetate. The combined organic layers were dried
over Na2SO4 and concentrated. The yields were determined by 1H
NMR spectroscopy with trichloroethylene (900 μL, 10 mmol) as an
internal standard. Then, the desired cross-coupled esters were iso-
lated by silica gel column chromatography with hexane/ethyl ac-
etate (5/1–10/1) as the eluent to afford the isolated yield.
After the successful synthesis and characterized of sodium
organoaluminate complex by NMR and X-ray crystallography, the
above heterobimetallic complex stabilized by bidentate pyrrolyl lig-
and as catalysts for Tishchenko reactions were studied. And the
results are listed in Table 1. The reaction was treated using ben-
zaldehyde as a model substrate in hexane solution with different
amounts of catalysts (1, 2, 5 mol%) at 30 °C within 3 h (entries 1–
3). We found when the amount of catalyst is increased to 5 mol%,
the yield of ester is no longer increased obviously. And the best
temperature for obtaining a satisfactory isolated yield (87%) was
50 °C (entries 4–5). Different solvents, including toluene, tetrahy-
drofuran, benzene and diethyl ether were screened, including the
solvent-free reaction (Table 1, entries 7–11). Neat conditions were
found to optimum for this reaction, which indicated that the sol-
vent did not play a critical role in reactivity of the reaction. Fur-
thermore, shortening the reaction time to 6 h gave a 92% isolated
yield of benzyl benzoate (entry 12).
3. Results and discussion
3.1. Synthesis and crystal structure of sodium organoaluminate
complex
Recently, we have reported that the synthesis and characteri-
zation of the lithium and potassium organoaluminate complexes
bearing bidentate pyrrolyl ligands [6]. To compare the structure
performance of alkali-metal organoaluminate complexes, we did
our best to obtain a novel sodium organoaluminate complex ac-
cording to the same method. Fortunately, the sodium organoalu-
minate was obtained through the addition of half the amount of
Al(CH3)3 at room temperature to a freshly prepared solution of NaL
(L= [C4H3NH(2-CH2NHtBu)]) (Scheme 1). And it was characterized
by elemental analysis, NMR spectroscopy analysis and single crys-
tal X-ray diffraction. It shows poor solubility in hexane. The cor-
Having realized the optimized conditions for benzaldehyde
dimerization, the substrate scope of this dimerization with a va-
riety of aromatic substrates were investigated (Table 2). These
aldehydes containing electron donating substituents and electron
withdrawing group in the para substituted aromatic ring were
tolerated, and the corresponding esters were obtained in good
isolated yields in reasonable time. (2a-2e). Benzaldehyde with
stronger electron-withdrawing group, 4-nitrobenzaldehyde was rel-
atively inert and only giving the desired products (2f) in 68%
isolated yield. Furthermore, this sodium organoaluminate com-
2

Y. Liu, Z. Guo and Y. Wang
Journal of Organometallic Chemistry 945 (2021) 121882
Fig. 1. (a) The ORTEP view of sodium organoaluminate complex, with the atom-numbering scheme and displacement ellipsoids drawn at the 25% probability level; (b)
Section of the extended framework structure by bridging interaction between sodium and pyrrolyl ring. Hydrogen atoms are omitted for clarity.
plex could catalyzed intramolecular Tishchenko reaction with o-
Table 1
Optimization of Tishchenko reaction catalyzed by sodium organoaluminatea.
phthalaldehyde, and gave a moderate yield of the corresponding
ester (2 g). Additionally, this protocol could be applied to hete-
rocyclic aldehydes, such as furfural and 2-pyridine aldehyde were
also dimerized into heterocyclic ester (2 h and 2i) in 57 and 60%
yield, respectively, although with lower efficiency.
The high catalytic behavior of the sodium organoaluminate
complex in the Tishchenko reaction promoted us to undergo
further investigation. Considering the fact that heterobimetallic
ate complexes could promote chemoselective ortho-reactions, the
crossed Tishchenko reaction between p-substituted benzaldehyde
and o–bromo or o-methoxybenzaldehyde was selected as the
model substrate to test the activities of sodium organoaluminate
complex. As shown in Table 3, when p-substituted benzaldehyde
was treated with 1 equivalent of o-substituted benzaldehyde in the
presence of 2 mol% catalyst at 50 °C for three hour, it gave the cor-
responding cross-coupled ester in a moderate yield of 41–73%. Fur-
ther detailed studies on this selective mechanism and to expand
the utility of this system are in progress in our group.
Entry
Temp. ( °C)
Solvent
Time (h)
Yield(%)d
1b
2
3c
30
30
30
50
70
50
50
50
50
50
50
50
Hexane
Hexane
Hexane
Hexane
Hexane
Hexane
None
3
3
3
3
3
6
3
3
3
3
3
6
47
75
76
87
86
82
91
85
89
86
90
92
4
5
6
7
8
Tolune
THF
9
10
11
12
Benzene
Et2O
None
Reaction conditions: aldehyde (10 mmol), catalyst (2% mmol),
50 °C, 3 h, yields determined by 1H NMR spectroscopy with
trichloroethylene as an internal standard. isolated yields were
given in parentheses.
a
Reaction conditions: benzaldehyde (102 uL, 10 mmol), sodium organoalu-
minate (0.076 g, 0.2 mmol), 3 h.
b
The catalyst amount is 1 mol%.
c
The catalyst amount is 5 mol%.
d
Isolated yield.
3

Y. Liu, Z. Guo and Y. Wang
Journal of Organometallic Chemistry 945 (2021) 121882
Table 2
Tishchenko reactions of aromatic aldehydes catalyzed by sodium organoaluminatea.
a
Reaction condition: the catalyst amount is 2 mol%, the yield is isolated yield, solvent-free, 50 °C, 3 h.
Table 3
The selective crossed-Tishchenko reactions catalyzed by sodium organoaluminate.
4

Y. Liu, Z. Guo and Y. Wang
Journal of Organometallic Chemistry 945 (2021) 121882
4. Conclusions
M. Tamm, M.S. Eisen, Mixed imidazolin-2-iminato–Cp∗ thorium(IV) complexes:
synthesis and reactivity toward oxygen-containing substrates, Organometallics
34 (12) (2015) 2933–2942; l) I.S.R. Karmel, N. Fridman, M. Tamm, M.S. Eisen,
Mono(imidazolin-2-iminato) actinide complexes: synthesis and application in
the catalytic dimerization of aldehydes, J. Am. Chem. Soc. 136 (49) (2014)
17180–17192; m) Y. Hoshimoto, M. Ohashi, S. Ogoshi, Catalytic transformation
of aldehydes with nickel complexes through η2 coordination and oxidative cy-
clization, Acc. Chem. Res. 48 (6) (2015) 1746–1755; n) D.G. Gusev, Dehydrogena-
tive coupling of ethanol and ester hydrogenation catalyzed by pincer-type YNP
complexes, ACS Catal. 6 (10) (2016) 6967–6981; o) Z. Guo, X. Wei, H. Tong,
J. Chao, D. Liu, The promoted Tishchenko reaction and catalytic intermedi-
ate by 2-aminopyrrolyl dilithium compounds, J. Organomet. Chem. 783 (2015)
73–76; p) Z. Guo, S. Wang, X. Wei, Aluminum complexes of β-hydroxy-imino
ligands: synthesis, structures and application in the Tishchenko reaction, J.
Organomet. Chem. 818 (2016) 115–122; q) V.M. Foley, C.M. McSweeney, K.S. Ec-
cles, S.E. Lawrence, G.P. McGlacken, Asymmetric aldol–Tishchenko reaction
of sulfinimines, Org. Lett. 17 (22) (2015) 5642–5645; r) T. Chen, K.-.H. Alt-
mann, Directed hydrogenations and an ireland–claisen rearrangement linked
to evans–Tishchenko chemistry: the highly efficient total synthesis of the ma-
rine cyclodepsipeptide doliculide, Chem. Eur. J. 21 (23) (2015) 8403–8407; s)
K.J. Kadassery, S.N. MacMillan, D.C. Lacy, Bisphosphine phenol and phenolate
complexes of Mn(i): manganese(i) catalyzed Tishchenko reaction, Dalton Trans.
47 (36) (2018) 12652–12655; t) G. Bauer, D. Ongari, X. Xu, D. Tiana, B. Smit,
M. Ranocchiari, Metal–organic frameworks invert molecular reactivity: lewis
acidic phosphonium zwitterions catalyze the aldol-Tishchenko reaction, J. Am.
Chem. Soc. 139 (50) (2017) 18166–18169; u) D.G. Gusev, D.M. Spasyuk, Re-
vised Mechanisms for Aldehyde Disproportionation and the Related Reactions
of the Shvo Catalyst, ACS Catal. 8 (8) (2018) 6851–6861; v) D.H. Nguyen, X. Triv-
elli, F. Capet, Y. Swesi, A. Favre-Réguillon, L. Vanoye, F. Dumeignil, R.M. Gauvin,
Deeper mechanistic insight into Ru pincer-mediated acceptorless dehydrogena-
tive coupling of alcohols: exchanges, intermediates, and deactivation species,
ACS Catal. 8 (5) (2018) 4719–4734; w) H. Liu, M.S. Eisen, Facile Coupling of Alde-
hydes with Alcohols: an evolved Tishchenko process for the preparation of un-
symmetrical esters, Eur. J. Org. Chem. 2017 (32) (2017) 4852–4858; x) K. Paudel,
B. Pandey, S. Xu, D.K. Taylor, D.L. Tyer, C.L. Torres, S. Gallagher, L. Kong, K. Ding,
Cobalt-catalyzed acceptorless dehydrogenative coupling of primary alcohols to
esters, Org. Lett. 20 (15) (2018) 4478–4481; y) H. Liu, M. Khononov, N. Fridman,
M. Tamm, M.S. Eisen, Synthesis, characterization and catalytic performances of
benzimidazolin-2-iminato actinide (IV) complexes in the Tishchenko reactions
for symmetrical and unsymmetrical esters, J. Organomet. Chem. 857 (2018)
123–137; z) V.Nevalainen Simpura, Symmetric esters by Tischtschenko reaction
of aldehydes catalyzed by bi- and tridentate catalysts derived from catechol or
gallol, trimethylaluminum and isopropanol, Tetrahedron 57 (2001) 9867–9872.
[3] a) Y. Hoshimoto, M. Ohashi, S. Ogoshi, Nickel-catalyzed selective conversion of
two different aldehydes to cross-coupled esters, J. Am. Chem. Soc. 133 (13)
(2011) 4668–4671; b) R. Doi, K. Kikushima, M. Ohashi, S. Ogoshi, Synthesis,
characterization, and unique catalytic activities of a fluorinated nickel enolate, J.
Am. Chem. Soc. 137 (9) (2015) 3276–3282.
In summary, we have demonstrated the synthesis and catalytic
activity of a new sodium organoaluminate complex stabilized by 2-
aminopyrrolyl ligand. According to X-ray analysis, the synthesized
sodium organoaluminate complex is a monodimensional infinite
chain structures with linear arrangements. It was proved to an ef-
ficient catalyst for the Tishchenko reaction. More importantly, this
system can be applied to various combinations of p-substituted
benzaldehyde with equimolar amounts of o-substituted benzalde-
hyde, and the corresponding cross-coupled esters are obtained in a
high selective manner.
Declaration of competing interest
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared to
influence the work reported in this paper.
Acknowledgements
Financial supports from the Coal-based Key Scientific and Tech-
nological Project (No. MH2014–07) and the Natural Science Foun-
dation of Shanxi Province (No. 201801D121041) are gratefully ac-
knowledged.
Supplementary materials
Supplementary material associated with this article can be
found, in the online version, at doi:10.1016/j.jorganchem.2021.
121882.
References
[1] L. Claisen, Ueber die einwirkung von natriumalkylaten auf benzaldehyd, Ber.
Dtsch. Chem. Ges. 20 (1) (1887) 646–650.
[2] a) R. Dhanya, S. Thomas, S. Saranya, G. Anilkumar, Recent advances and
prospects in the Tishchenko reaction, Chem. Select
5 (2020) 754–763; b)
S.A. Morris, D.G. Gusev, Rethinking the Claisen–Tishchenko reaction, Angew.
Chem. Int. Ed. 56 (22) (2017) 6228–6231; c) A.M. Whittaker, V.M. Dong, Nick-
el-catalyzed dehydrogenative cross-coupling: direct transformation of aldehy-
des into esters and amides, Angew. Chem. Int. Ed. 54 (4) (2015) 1312–1315;
d) H. Viana, E.P. Carreiro, A. Goth, P. Bacalhau, A.T. Caldeira, M.d.R. Martins,
A.J. Burke, Sequential alcohol oxidation/putative homo Claisen–Tishchenko-type
reaction to give esters: a key process in accessing novel biologically active lac-
tone macrocycles, RSC Adv. 6 (68) (2016) 63214–63223; e) M. Teci, N. Lentz,
E. Brenner, D. Matt, L. Toupet, Alkylfluorenyl substituted N-heterocyclic carbenes
in copper(i) catalysed hydrosilylation of aldehydes and ketones, Dalton Trans
44 (31) (2015) 13991–13998; f) L. Souillart, N. Cramer, Highly Enantioselective
Rhodium(I)-catalyzed carbonyl carboacylations initiated by C-C bond activation,
Angew. Chem. Int. Ed. 53 (36) (2014) 9640–9644; g) V. Ritleng, M. Henrion,
M.J. Chetcuti, Nickel N-heterocyclic carbene-catalyzed C–heteroatom bond for-
mation, reduction, and oxidation: reactions and mechanistic aspects, ACS Catal.
6 (2) (2016) 890–906; h) L.M. Orozco, M. Renz, A. Corma, Carbon–carbon bond
formation and hydrogen production in the ketonization of aldehydes, Chem-
SusChem 9 (17) (2016) 2430–2442; i) F. Lin, Y.-.H. Chin, Alkanal transfer hydro-
genation catalyzed by solid Brønsted acid sites, J. Catal. 341 (2016) 136–148; j)
N.V. Kulkarni, A. Das, S.G. Ridlen, E. Maxfield, V.A.K. Adiraju, M. Yousufuddin,
H.V.R. Dias, Fluorinated triazapentadienyl ligand supported ethyl zinc(ii) com-
plexes: reaction with dioxygen and catalytic applications in the Tishchenko re-
action, Dalton Trans. 45 (11) (2016) 4896–4906; k) I.S.R. Karmel, N. Fridman,
[4] a) C.J. O’ Connor, F. Manoni, S.P. Curran, S.J. Connon, Microwave-assisted efficient
thiolate-catalysed homo- and crossed intermolecular Tishchenko reactions, New
J. Chem. 35 (3) (2011) 551–553; b) S.P. Curran, S.J. Connon, The thiolate-cat-
alyzed intermolecular crossed Tishchenko reaction: highly chemoselective cou-
pling of two different aromatic aldehydes, Angew. Chem. Int. Ed. 51 (43) (2012)
10866–10870; c) S.P. Curran, S.J. Connon, Selenide Ions as Catalysts for Homo-
and Crossed-Tishchenko Reactions of Expanded Scope, Org. Lett. 14 (4) (2012)
1074–1077.
[5] Z. Guo, T. Pang, Y. Wang, Y. Zhang, X. Wei, Alkali-metal organomagnesiate com-
plexes as catalysts for highly chemoselective crossed-Tishchenko reactions, Dal-
ton Trans. 49 (19) (2020) 6418–6424.
[6] a) Z. Guo, L. Yan, Y. Liu, X. Wu, X. Wei, Potassium organoaluminate: synthesis,
structure, and catalytic activity for the conversion of CO2 into cyclic carbon-
ates, J. Organomet. Chem. 922 (2020) 121365; b) Z. Guo, Y. Xu, J. Chao, X. Wei,
Lithium organoaluminate complexes as catalysts for the conversion of CO2 into
cyclic carbonates, Eur. J. Inorg. Chem. 2020 (29) (2020) 2835–2841.
[7] C.S.B. Gomes, D. Suresh, P.T. Gomes, L.F. Veiros, M.T. Duarte, T.G. Nunes,
M.C. Oliveira, Sodium complexes containing 2-iminopyrrolyl ligands: the in-
fluence of steric hindrance in the formation of coordination polymers, Dalton
Trans 39 (3) (2010) 736–748.
5