Palladium nanoparticle-incorporated mesoporous organosilica (MCM-41-Crown.Pd) was synthesized via the grafting of dibenzo-18-crown-6-ether moieties on the MCM-41 surface, followed by reaction of the nanocomposite with palladium acetate and then its reduction in ethanol. The cavity of the immobilized dibenzo-18-crown-6 as host material can stabilize the palladium nanoparticles effectively and prevent their aggregation and separation from the surface. The structure of the nanocomposite was characterized using various techniques. The catalytic properties of the nanocomposite in the Heck coupling reaction, one of the most useful transformations in organic synthesis, between aryl halides and olefins in water were also explored. The main advantages of the method are low cost, high yields, easy work-up and short reaction time. The nanocatalyst can be easily separated from a reaction mixture and was successfully examined for seven runs, with a slight loss of catalytic activity.

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The synthesis of a series of known β-aminocyclohexanones has been accomplished using pentaerythrityl tetramethyl imidazolium phosphotungstate (C(MIM-PTA)4) as a new tetradentate acidic catalyst.

A new mesoporous organic-inorganic nanocomposite was formulated and then used as stabilizer and support for the preparation of palladium nanoparticles (Pd NPs). The properties and structure of Pd NPs immobilized on prepared 1,4-diazabicyclo[2.2.2]octane (DABCO) chemically tagged on mesoporous γ-Fe 2 O 3 @hydroxyapatite (ionic modified (IM)-MHA) were investigated using various techniques. The synergistic effects of the combined properties of MHA, DABCO and Pd NPs, and catalytic activity of γ-Fe 2 O 3 @hydroxyapatite-DABCO-Pd (IM-MHA-Pd) were investigated for the Heck cross-coupling reaction in aqueous media. The appropriate surface area and pore size of mesoporous IM-MHA nanocomposite can provide a favourable hard template for immobilization of Pd NPs. The loading level of Pd in the nanocatalyst was 0.51 mmol g −1 . DABCO bonded to the MHA surface acts as a Pd NP stabilizer and can also lead to colloidal stability of the nanocomposite in aqueous solution. The results reveal that IM-MHA-Pd is highly efficient for coupling reactions of a wide range of aryl halides with olefins under green conditions. The superparamagnetic nature of the nanocomposite means that the catalyst to be easily separated from solution through magnetic decantation, and the catalytic activity of the recycled IM-MHA-Pd showed almost no appreciable loss even after six consecutive runs.KEYWORDS aqueous media, Heck coupling reaction, mesoporous ionic-modified γ-Fe 2 O 3 @hydroxyapatite, palladium nanoparticle, sustainable organometallic platform