*2.6.1 HIL on mesoporous solids*

*Solvents, Ionic Liquids and Solvent Effects*

field [20].

**2.5 Polymer-supported HIL**

*2.4.5 Ni supported on magnetic nanoparticles (MNPs)*

Ni2+ ion containing 1-methyl-3 (trimethyoxsilylpropyl)imidazolium chloride IL was impregnated on magnetic F3O4 NP. Heck reaction was conducted at 100°C (**Figure 7**). IL catalyst separated by magnet can be reused several times after washing without loss of activity. IL immobilized on magnetic particles is an excellent technology for catalytic reactions and separation technologies with substantive progress. The combination of MNPs and ILS gives a magnetic supported IL, which exhibits the dual properties of IL as well as facile separation by magnetic external

A polymer-supported catalyst was prepared, which exhibited high catalytic activity. Copolymerization of 1-vinyl-3-butylimidazolium with styrene gave polymer supports to immobilize Pd(OAc)2 using a method of alcohol reduction. The Pd existed as NP of less than 6 nm in these copolymers. This copolymer-supported Pd was efficient and a reusable catalyst for the Heck reaction in aqueous media in the absence of any phase transfer catalysts (PTCs) or ligands (**Figure 8**). The catalyst

could be reused for three cycles without depletion of yield [21].

**134**

**Figure 8.**

**Figure 7.**

*Polymer-supported HIL [21].*

*Ni supported on magnetic nanoparticles [20].*

Palladium-containing nanoparticles were immobilized to attain heterogeneity on the mesoporous nanoparticles, namely SBA-15 using an ionic liquid, namely 1.1.3.3-tetramethylguanidinium lactate. Very interestingly, this immobilized Pd catalyst was exploited for solvent-free Heck-type coupling reactions and showed excellent activity and reusability. No deactivation was observed even after six recycles. High yields were achieved even with very low catalyst loading 0.001% of Pd, which is remarkable. Leaching occurs during the reaction, but the Pd gets redeposited on the surface at the end of the reaction with the help of TMG (1,1,3,3-tetramethylguanidine) moiety, excellent stabilizer for metallic NPs [23]. Pd acetate was immobilized on amorphous silica with the aid of an IL, namely [bmim]PF6. This immobilized catalyst was highly efficient for the Mizoroki-Heck reaction of various aryl halides with cyclohexyl acrylate in dodecane as solvent. A TON of 68,400 and TOF of 8000 h<sup>−</sup><sup>1</sup> were achieved in the reaction of iodobenzene with cyclohexyl acrylate. The recyclability of the catalyst was lost after three cycles. Leaching studies showed loss of less than 0.24% Pd [9]. This methodology is presented in **Figure 9**.

### *2.6.2 Encapsulated heterogenous ionic liquids*

Pd(OAc)2 was immobilized on amorphous silica or alumina with the aid of an ionic liquid (Pd-SILC—Pd supported ionic liquid catalyst). The catalytic materials immobilized on N,N-diethylamino propylated (NDEAP) alumina or silica with or without bmimPF6 gave the best results for the Suzuki-Miyaura coupling of aryl halides with arylboronic to yield the respective biphenyls. The synthesis of the encapsulated heterogeneous ionic liquid and the reaction were represented below (**Figure 10**). It was found out that the immobilization with the aid of an IL, bmimPF6 was essential for inhibiting leaching of Pd(OAc)2. The catalyst gave 95%

**Figure 9.** *HIL on mesoporous solids—Mizoroki-Heck reaction.*

**Figure 10.** *Suzuki-Miyaura reaction catalyzed by immobilized Pd catalyst on reversed phase alumina [24].*

average yield in reuse studies up to five times though catalyst activity was gradually lost. High efficiency of the catalyst was exhibited by a TON of 2 million and TOF of 30,000 h<sup>−</sup><sup>1</sup> in the reaction of 4-bromo acetophenone and phenyl boronic acid [24].
