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Catalysis Science & Technology
Page 2 of 11
DOI: 10.1039/C6CY01771A
ARTICLE
Journal Name
Supported chlorometallate ionic liquids, such as network with bimodal system of macropores of micrometer
chloroaluminates(III),13 chloroindates(III),14 chloroferrates(III) size. In a typical procedure 8.7 g of polyethylene glycol (PEG)
and chlorostannates(II)15 were extensively studied as catalysts with molecular weight of 35.000 g/mol was dissolved in 100 ml
in Friedel–Crafts alkylation and acylation. In all cases, high of 1M HNO3 Sol was stirred until a clear solution was obtained.
efficiency, good stability and the possibility of recycling were Then 83 ml tetraethoxysilane was added slowly and after that
demonstrated. The performance of SILPs was typically better, 3.84 g of cetylotrimethylammonium bromide. This solution
and sometimes on par with that of free ionic liquids. was left to gel at 40 °C and aged for 10 days at the same
Surprisingly, there is only a single report on the application of temperature Next the white alcogels obtained were
chlorometallate SILPs for the Diels-Alder. Lewis acidic impregnated in a 1 M NH4OH solution for 9 h at 90 °C, washed
chloroaluminate(III) ionic, synthesised from poly(4- with deionised water, dried for 4 days at room temperature
vinylpyridine) or poly(1-vinylimidazole) polymers, exhibited and then calcined at 550 °C for 8 h under air (heating ramp 0.5
similar activity and selectivity to the homogeneous analogue.16 K/min). The size and shape of the monoliths were determined
The reaction was carried out in toluene and the selectivity by the size and shape of the vessel used. Composition led to
endo:exo product was 61:39. The polymer-supported the formation of
chloroaluminate(III) catalysts was recycled five times, with a network with bimodal system of macropores of micrometer
20% loss of initial activity. size. Apart from the macropores, the material also exhibited
a macroporous, interconnected, open
In this work, we explored the catalytic potential of textural mesopores, with BET surface area of 300 m2/g, total
chlorogallate(III) and chloroaluminate(III) ionic liquids pore volume – 3.5-4 cm3/g and mean mesopore diameter of
supported on silica by covalently bound cations, under about 20 nm (determined by nitrogen adsorption), macropore
solventless conditions.
diameter 30-50 µm. The SEM picture of silica support SiO2 is
presented in ESI.
Synthesis of 1-methyl-3-(triethoxysilyl-propyl)imidazolium
Experimental
chlorometallate(III) ionic liquids, [tespmim][MnCl(3n+1)
]
Materials and methods
All chlorometallate ionic were prepared according to the
general procedure, at a 1 g scale.19 Appropriate amounts of dry
[tespmim]Cl were placed in a round bottom flask equipped
with a stirring bar. Then metal chloride MCl3 (where M = Al or
Ga) was added slowly, with stirring to achieve the desired
composition, and then allowed to fully react (1000 rpm, 3 h, 60
°C). All reactions were carried out under dry inert gas. Exact
amounts of reactants are listed in Table 1.
All reactants were purchased from Sigma-Aldrich and used as
received, unless otherwise stated. Dichloromethane was
distilled from P2O5 and stored over activated 3Å molecular
sieves. All metal chlorides were anhydrous, 99.99% purity,
packed in ampules under inert gas. SiO2-type silica material17,18
and 1-methyl-3(triethoxysilylpropyl)imidazolium chloride17
were prepared according to the literature.
Synthesis
of
1-methyl-3-(triethoxysilyl-propyl)imidazolium
Synthesis of 1-methyl-3-(triethoxysilyl-propyl)imidazolium
chlorometallate(III) ionic liquids anchored on the silica support,
chloride, [tespmim]Cl
The mixture of 0.12 mol (3-chloropropyl)triethoxysilane and
0.12 mol of 1-methylimidazole (freshly distilled) was refluxed
at 78 °C for 24 h under nitrogen atmosphere. The reaction
mixture was cooled down and any remaining volatile
substances were removed by rotary evaporation. The crude
product was additionally washed with Et2O (5x5 ml) and dried
under vacuum. The product (slightly yellow viscous oil) was
obtained with 98% yield.
SiO2-[tespmim][MnCl(3n+1)
]
SiO2 (1 g) was suspended in dry toluene (5 cm3). Next, 1.55
mmol of ionic liquid: [tespmim][Al2Cl7] or [tespmim][Ga3Cl10],
was added. Two-necked round-bottomed flask was equipped
with a nitrogen-filled balloon, closed with a septum and stirred
at 80 °C for 3 h. Subsequently, toluene was removed under
vacuum and the catalyst was dried for 4 h at 80 °C under
reduced pressure. To verify ionic liquids immobilisation
efficiency ICP, solid state 1H, 13C, 29Si and 27Al NMR were
performed.
1H NMR (600 MHz, CDCl3, TMS): d = 10.66 (s, 1H), 7.36 (m,
1H), 7.59 (m, 1H), 4.34 (t, 2H, J = 7.40 Hz), 4.14 (s, 3H), 3.82 (4,
6H, J = 7.40 Hz), 2.05 (m, 2H), 1.20 (t, 9H, J = 7.80 Hz), 0.61 (m,
2H); 13C NMR (300 MHz, CDCl3, TMS): d = 138.13, 123.34, Table 1. The amounts of reactants used for the synthesis of chlorometallate
ionic liquids
121.58, 58.53, 51.66, 36.51, 24.32, 18.2, 7.03. Anal. Calcd.: C,
48.45; H, 8.39; N, 8.69. Found: C, 48.34; H, 8.30; N, 8.77.
Chlorometallate
ionic liquid
[tespmim]Cl,
mmol
MCl3,
mmol
a
χMCl3
General procedure for synthesis of silica support (SiO2) with the
extensive system of meso- and macropores
[tespmim][AlCl4]
[tespmim][Al2Cl7]
[tespmim][GaCl4]
[tespmim][Ga2Cl7]
0.50
0.67
0.50
0.67
0.75
2.19
1.70
2.00
1.48
1.17
2.19
3.39
2.00
2.96
3.52
The synthesis of support using porogenes of different sizes
(polyethylene glycol and cetyltrimethylammonium bromide),
together with the induction and freezing of the transition
structures originating from the phase separation process, led
to the formation of a macroporous, interconnected, open
[tespmim][Ga3Cl10
]
aχMCl3-molar ratio of metal chloride in ionic liquids
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
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