Heterogenization of homogeneous catalytic systems

Synthesis, characterisation and reactivity of water-soluble ferrocenylimine-Rh(I) complexes as aqueous-biphasic hydroformylation catalyst precursors

“…The mononuclear complex (5) was successfully prepared through a one-pot synthesis by the Schiff-base condensation reaction of monosodium 3-t butyl-5-sulfonatosalicylaldehyde (2) with hydrazine monohydrate and ferrocenecarboxaldehyde (Scheme 2). Complex (5) was isolated as a dark brown solid in good yield (82%), with the ferrocenylcarbaldehyde hydrazone as a by-product. Both complexes (4 and 5) are new and have shown good solubility in water (1.82 mg/mL and 4 mg/mL, respectively).…”

“…Preparation of 3-t butyl-5-sulfonato salicylaldimine-ferrocenylimine complex (5) Hydrazine hydrate (0.187 g, 3.729 mmol) was added dropwise to a stirring solution of 3-t butyl-5-sulfonatosalicylaldehyde (1.05 g, 3.729 mmol) in methanol and the reaction heated for 6 h at 45 C. Ferrocenecarboxaldehyde (0.799 g, 3.731 mmol) was then added and the reaction mixture heated at 45 C for 24 h. The dark brown solution was filtered by gravity to remove an orange precipitate, the ferrocenylcarbaldehyde hydrazone (see supplementary material for characterisation data). The volume of the filtrate was then reduced to ca.…”

“…However, due to the greater expense of rhodium, novel strategies are required to ensure element sustainability. The aqueous-biphasic system is ideal as it utilises water, which is an eco-and user-friendly, relatively cheap, abundant and non-flammable solvent, in line with Green Chemistry Principles [3,5]. In addition, water is immiscible with most organic solvents, alleviating some of the challenges associated with homogeneous catalysis, such as long chain aldehyde product recovery.…”

Porous Carbon Nanosheet‐Supported Chiral Squaramide for Highly Enantioselective Friedel–Crafts Reaction

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Porous carbon nanosheets (PCNs) wereu sed for the first time as as upport to immobilize aq uinine-squaramide catalyst for the asymmetric Friedel-Craftsa ddition of pyrazolonest oi satin ketimines. Nevertheless,h eterogenized chiral catalysts achievedb yt he surfacec ovalentt ethering strategy usually exhibit poor enantioselectivity owing to limited free space for chiral induction [2] and uncontrolled activity owing to certain side reactions initiated by the supports. Recycling batch reactions together with ac ontinuous flow process confirmedt he stabilityo ft he catalyst.

The heterogenization of homogeneous chiral catalysts is considered an effective approach towards sustainable asymmetric synthesis.

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Tethering of Dinuclear Complexes to SBA‐15 and Their Application in CO2 Hydrogenation

“…In general, this "heterogenisation" has taken place using differential catalyst solubility approaches, [24][25] as well as through the use of non-covalent, [26][27] or covalent, [27][28][29][30][31][32][33] interactions between the molecular catalyst and the surface of the solid material either following modification of the surface of the solid or the catalytic material or both.…”