On the activity of chiral chromium salen complexes covalently bound to solid silicates for the enantioselective epoxide ring opening

Baleizão, Carlos; Gigante, Bárbara; Sabater, Marı́a J.; Garcı́a, Hermenegildo; Corma, Avelino

doi:10.1016/s0926-860x(01)00979-6

Cited by 93 publications

(67 citation statements)

References 23 publications

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“…137 Following this anchoring approach, Schiff bases complexes were stabilized onto MWW individual layers from ITQ-2 delaminated zeolites, generating active asymmetric catalysts for enantioselective epoxide ring opening reactions when grafted chromium salen complexes were incorporated. 138 Similarly, chiral delaminated ITQ-2 zeolites were formed by anchoring stabilized salen (Pd and Ni) complexes, being effectively used (TOFs around 200x10 3 h -1 ) to catalyze the hydrogenation of imines or alkenes, 139,140 and for Heck and Suzuki coupling reactions under phosphine-free conditions. 141 Inside this line, epoxidation of several prochiral alkenes was favored by grafting Mn(II) salen complexes onto delaminated ITQ-2 support zeolites through axial coordinating ligands.…”

Section: 131mentioning

confidence: 99%

Layered zeolitic materials: an approach to designing versatile functional solids

2014

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Section: 131mentioning

confidence: 99%

Layered zeolitic materials: an approach to designing versatile functional solids

2014

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“…18 This is the case of hybrid materials derived from delaminated zeolites, such as ITQ-2 and ITQ-6, in which specific organocatalysts, containing acid, base or chiral centers, are covalently supported onto MWW or ferrieritic individual layers. 19,20,21 Another possibility has been the incorporation, as stable pillars, of organic functional fragments in the interlayer space, generating ordered hybrid materials with high reactant accessibility owing to the additional mesoporous galleries created between the inorganic zeolitic sheets ( Figure S1). These approaches have been very effective to heterogenize different homogeneous catalysts without appreciable activity loss.…”

Section: Introductionmentioning

confidence: 99%

One-pot synthesis of hierarchical porous layered hybrid materials based on aluminosilicate sheets and organic functional pillars

et al. 2014

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Layered hybrid materials (LHMs) based on ordered silicoaluminate sheets linked with organic fragments, perpendicularly located and stabilized in the interlayer space, were synthesized by one-pot direct hydrothermal process, in absence of structural directing agents (SDAs), and using bridged silsesquioxanes as organosilicon precursors. By following the synthesis described here, the preliminary preparation of inorganic layered precursors, post-synthesis swelling and/or pillaring treatments can be avoided. The physico-chemical and structural characteristics of the materials were studied by chemical and thermogravimetrical analyses, X-ray diffraction, TEM microscopy, spectroscopic techniques (NMR and FTIR) and textural measurements. The complete exchange of intracrystalline sodium cations by protons, without substantial structural alteration of hybrid materials, facilitated the generation of hybrid materials, which contained acid and base sites located in the inorganic (silicoaluminate layers) and in the organic interlayer linkers, respectively, being the resultant acid-base materials active and selective catalysts.

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“…On the contrary, for the solids in which the complex was covalently attached to the surface then it was not observed leaching, being the e.e. more reduced (<20%) compared to those obtained in homogeneous catalysis (>50%) (Scheme 8) [57].…”

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confidence: 93%

Layered Materials with Catalytic Applications: Pillared and Delaminated Zeolites from MWW Precursors

Díaz

2012

ISRN Chemical Engineering

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Delaminated and pillared zeolites are an innovative family of molecular sieves which introduced a different concept inside the synthesis of active catalysts or inorganic supports. These types of materials exhibit an elevated accessibility due to their open structure, characterized by the high external surface area without imposed restrictions controlled by the pore sizes. These open zeolites are conformed by crystalline ordered (pillared zeolites) or disordered (delaminated zeolites) individual layers, exhibiting textural properties which are favorable to carry out catalytic processes in which it is necessary to employ catalysts with completely accessible active sites. The elevated external surface area of these zeolites is profitable to generate more specific organic-inorganic materials, acting in this case as stable inorganic matrixes. The preparation of this open type-zeolites family is based on the modification of, previously synthesized, zeolitic precursors which are preexpanded to obtain the final delaminated or pillared zeolites which exhibit very different physicochemical properties compared with the starting precursors. Along this paper, the most relevant MWW-type high accessible zeolitic materials will be considered. Their nature, characteristics, and reactivity will be shown in the function of the employed synthesis method for their preparation and the postsynthesis treatments carried out, tuning their properties.

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On the activity of chiral chromium salen complexes covalently bound to solid silicates for the enantioselective epoxide ring opening

Cited by 93 publications

References 23 publications

Layered zeolitic materials: an approach to designing versatile functional solids

Layered zeolitic materials: an approach to designing versatile functional solids

One-pot synthesis of hierarchical porous layered hybrid materials based on aluminosilicate sheets and organic functional pillars

Layered Materials with Catalytic Applications: Pillared and Delaminated Zeolites from MWW Precursors

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