Abstract
Zirconium phosphate glycine diphosphonate nanosheets (ZPGly) have been used as support for the preparation of solid palladium nanoparticles, namely Pd@ZPGly. Thanks to the presence of carboxy-aminophosponate groups on the layer surface, ZPGly-based materials were able to stabilize a high amount of palladium (up to 22 wt %) also minimizing the amount of metal leached in the final products of representative important cross-coupling processes selected for proving the catalysts’ efficiency. The catalytic systems have been fully characterized and used in low amounts (0.1 mol %) in the Suzuki–Miyaura and Heck cross-couplings. Moreover, the protocols were optimized for the use of recoverable azeotropic mixtures (aq. EtOH 96% or aq. CH3CN 84%, respectively) and in the flow procedure allowing one to isolate the final pure products, without any purification step, with very low residual palladium content and with a very low waste production.
Highlights
Palladium-catalyzed cross-coupling reactions of aryl halides with organo-boronic acids (Suzuki–Miyaura) and olefins (Heck) are extremely useful carbon–carbon bond formation tools widely investigated and applied in diverse areas such as natural products, agrochemicals, pharmaceutical intermediates and material science [1,2,3,4].A challenging issue for metal-catalyzed transformation is related to the actual recoverability and reusability of the catalytic system while avoiding the possible loss of the metal especially if as precious and exhaustive as palladium
We have studied the use of palladium nanoparticles on zirconium phosphate glycine diphosphonate nanosheets in the Suzuki–Miyaura and Heck cross-coupling reactions optimizing the reaction conditions in order to replace classic toxic polar aprotic media by using safer and recoverable azeotropic mixtures of CH3 CN/H2 O 84% and EtOH/H2 O 96%, respectively [39]
In order to reduce the leaching of Pd and the amount of waste and simplify the work-up procedure, we investigated the use of diethylaminomethyl-polystyrene (PS-TEA) as the heterogeneous base, which can be removed by simple filtration from the reaction mixture, and the isolation of the final product can be obtained by distillation of the azeotropic reaction medium
Summary
A challenging issue for metal-catalyzed transformation is related to the actual recoverability and reusability of the catalytic system while avoiding the possible loss of the metal especially if as precious and exhaustive as palladium. Over the past few years, considerable interest has been focused on supported palladium metallic nanoparticles (PdNPs) as an effective approach to achieve high catalytic activity, easy recovery, along with high stability [5,6,7,8,9]. The stability and durable catalytic efficiency of nanoparticles, which are very much related to the avoidance of their aggregation and/or their minimal metal leaching in the reaction products, are still a challenge [10,11]. A large number of supports have been used to stabilize the PdNPs, such as carbon materials [12,13,14], inorganic materials [15,16], MOFs [17,18], hybrid materials [19,20,21,22,23,24] and organic polymers [25,26,27].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
