*2.4.4 Phosphinite-functionalized magnetic nanoparticles (MNPs)*

*Solvents, Ionic Liquids and Solvent Effects*

type coupling reactions.

important reactions [18].

Palladium, forming complex (**Figure 4**). Chloro-functionalized γ-Fe2O3 was prepared by reacting Fe2O3 with chloropropyltrimethoxysilane. Treatment with DABCO gave the DABCO-γ-Fe2O3. Further reaction with Pd(OAc)2 gave the desired Pd-DABCO-γ-Fe2O3. This catalyst was proven to be a recyclable catalyst for Heck-

of the catalytic preparation and the reaction is depicted in **Figure 4**.

*Pd supported on amine-functionalized magnetic nanoparticles—Suzuki coupling [18].*

*2.4.3 Palladium supported on amine-functionalized magnetic nanoparticles*

Heck reactions were carried out with aryl iodobenzene to give high yields of the products in 30 min. Aryl bromide and chlorides also underwent the Heck-type coupling reactions but requiring longer reaction times of 12–24 h. The average isolated yield of 90% was retained for five consecutive runs [17]. An external magnet was used to separate the catalyst from the reaction mixture and reused at least five times without significant degradation in its catalytic activity. The pictorial representation

The issue of leaching could not be fully resolved in the SILP systems too; as a result, a convenient protocol was developed to recover the palladium catalyst magnetically. Magnetic nanoparticles (NPs) were functionalized to impart stronger bonding to the metal. Towards this end amine functionalized ILs were synthesized. Fe3O4 was coated with silica. This was then functionalized with (3-chloropropyl)triethoxysilane. The ionic liquid moiety was then easily anchored onto the surface of the SiO2/Fe3O4 to obtain amine-functionalized ionic liquid-modified magnetic NPs (IL-NH2/SiO2/Fe3O4). Excellent results were achieved with this catalyst for the Suzuki coupling of various aryl iodides and bromides (**Figure 5**). The authors claimed that the catalyst was well dispersed in the reaction medium, magnetically recovered from reaction mixture, and reused for several times without significant loss of activity. All these advantages make the protocol to be a green and convenient process for other metal catalyzed

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**Figure 5.**

In continuation of research on magnetite-supported palladium catalysts, the synthesis and characterization of phosphinite-functionalized magnetic nanoparticles containing imidazolium ionic liquid moiety for stabilization of palladium nanoparticles and its application as a catalyst in Suzuki-Miyaura coupling reactions were examined.

Fe3O4 NPs were coated with a thin layer of silica using tetraethyl orthosilicate to provide core shell Fe3O4 NP (SiO2@Fe3O4 NP). These NPs were then treated with glycidoxypropyltrimethoxysilane to afford epoxy functionalized SiO2@ Fe3O4. Further reaction with 1-methyl imidazole and chlorodiphenyl phosphine gave the Im-Phos-SiO2-@Fe3O4. The catalyst was then prepared by treating with PdCl2 (**Figure 6**). The catalyst was characterized by various methods. The obtained compound was characterized by SEM, TEM, EDX, solid UV, VSM, XRD, XPS, FT-IR and N2 adsorption-desorption analyses. Aryl bromides gave high yields in EtOH:water solvent. For aryl chlorides, the solvent was changed to DMF and, at 120°C, it gave high yields. Hot filtration test was carried out and showed that the catalyst was mostly heterogeneous. The catalyst was recyclable for at least eight times with little depletion of activity [19]. The scheme route of the catalyst is presented in **Figure 6**.

**Figure 6.** *Phosphinite-functionalized magnetic nanoparticles-Suzuki coupling [19].*
