نانوذرات Pd-Ni بر روی اکسید تیتانیوم برای واکنش های اتصال سوزوکی میورا Pd-Ni nanoparticles supported on titanium oxide as effective catalysts for Suzuki-Miyaura coupling reactions

1 Introduction Palladium-catalyzed Suzuki-Miyaura coupling reaction (SMR) is one of the most important approaches to form C–C bond. It has been widely applied to the synthesis of pharmaceutical intermediates, natural products, functional materials and biomolecules, due to its advantages such as mild reaction conditions and low toxicity [1–7]. Besides using organic ligands to finely tune catalytic activities of homogeneous Pd catalysts, reducing Pd particle size to nanoscale has also become a prevalent strategy to produce robust catalysts for the SMRs by increasing of atom efficiency, as other organic chemical reactions catalyzed by nanomaterials [3,8–10]. As a consequence, the SMRs catalyzed with Pd nanoparticles have received increasing attention in recent years. In comparison to homogeneous Pd catalysts, Pd nanoparticles can be readily separated from products and reused in succession without considerable loss of catalytic activity [11–17]. Nevertheless, from a practical point of view, it is still imperative to reduce the dosage of Pd catalyst for the SMR because of the limited reserves of noble metals. In this respect, the development of bimetallic nanoparticles, in particular palladium with non-noble metals, has many advances over the past few years [18,19]. Bimetallic nanocatalysts not only combine the properties of individual constituents but also may have enhanced catalytic activity, selectivity, and stability. This may be attributed to the modulation of the charge transfer between different metals and surface element distribution [20,21]. In this context, Pd-based bimetallic nanoparticles (NPs) have been widely used in various coupling reactions, such as polypropylenimine-grafted graphene supported Pd-Co alloy NPs for the Sonogashira reaction and a PVP-stabilized Au-Pd alloy for the Ullmann reaction [22,23]. Chen and coworkers demonstrated that Au-Pd@SiO2 with a core-shell structure of Au-Pd particles is better than monometallic palladium nanoparticles as a catalyst for the SMRs [24]. Muraviev and coworkers reported that a core-shell Pd@Co NPs based on cross-linked polymers showed enhanced catalytic activity and stability [25].