## 4 Conclusions  
We herein presented novel microsphere resins bearing well-defined Pd-SALOPHEN species on the surface, which were synthesized by a simple procedure to obtain high surface area polymer pre-catalysts with specific Brunauer-Emmett-Teller surface areas \(\geq\) 580 m\({}^{2}\cdot\)g\({}^{-1}\), and which operate by a typical Pd(II)/Pd(0) Heck catalytic cycle. Spectroscopic measurements (X-ray photoelectron spectroscopy, infrared spectroscopy, and diffuse reflectance spectroscopy ultraviolet-visible light measurements) confirmed the presence of the expected complexes following the polymerization process. These novel solid-based microsphere resin catalysts were both highly active and selective in the Heck coupling of iodobenzene with methyl acrylate (MA) to produce methyl cinnamate as the reaction product. Consequently, this study clearly demonstrated that the catalytic effect of the palladium N,N'-bis(3-alllysalicylidene)o-phenylenediamine complex (PdAS) loading in the resin formulation had a systematic influence on the formation of Pd nanoparticles on the catalyst surfaces. More specifically, a nominal loading of \(\geq\)2.0 wt.% PdAS as a metal chelate monomer in the catalyst resulted in the irreversible formation of Pd nanoparticles on the catalyst surfaces. Indeed, we found that PdAS(10)-MA (10 wt.% PdAS) exhibited a superior catalytic performance, and due to its heterogeneous nature, it could be easily separated from the reaction mixture and reused after washing without any significant loss in activity over at least five consecutive reaction cycles. We therefore expect that the described immobilization of a homogeneous catalyst will lead to further advances in such materials for application in additional catalytic processes.  
The following are available online at [[http://www.mdpi.com/1996-1944/12/16/2612/s1](http://www.mdpi.com/1996-1944/12/16/2612/s1)]([http://www.mdpi.com/1996-1944/12/16/2612/s1](http://www.mdpi.com/1996-1944/12/16/2612/s1)), Ligands and Pd-complexes synthesis, UV-vis of PdAS complex characterization, Scheme S1: Semi-Batch reactor used for the catalytic measurements, Figure S1: Microsphere diameter distribution of PdAS(x)-MA catalysts. (a) PdAS(1)-MA, (b) PdAS(2)-MA, (c) PdAS(5)-MA and (d) PdAS(10)-MA., Figure S2: Exponential fitting decrease curves of concentration of I-Ph on time for Pd-based catalysts. (a) Pd(CH\({}_{3}\)CO\({}_{2}\))\({}_{2}\), (b) Pd-SALOPHEN, (c) PdAS(1)-MA, (d) PdAS(2)-MA, (e) PdAS(5)-MA and (f) PdAS(10)-MA.  
[PERSON] performed the synthesis of materials; [PERSON] performed the SEM-EDS and DR UV-Vis solid state characterization. [PERSON] performed the design of the synthesis, characterization of materials, catalytic result analysis and wrote the manuscript; [PERSON] performed the characterization and catalytic result analysis and review and edits the manuscript.  
This research was funded by FONDECYT 1170083 (G.P.), FONDECYT Initiation 11170095 (C.H.C.), FONDECYT Initiation 11160468 (C.C.T.) and CONICYT PAI/Concurso Nacional insecion de Capital Humano Avanzado en la Academia Convocatoria ano 2017 PAI79170027 (C.C.T.).  
The authors thank to Unidad de Equipamiento Cientifico--MAINI, Universidad Catolica del Norte, for the XPS analysis (CONICYT-Programa FONDEQUIP XPS EQM 140044 2014-2016) and CONICYT Grant 21150195 (C.M.). We are grateful to [PERSON] and [PERSON] for ICP-OES analysis (Departament de Quimica Fisica i Inorganica, Universitat Rovira i Virgili, Tarragona--Spain).  
The authors declare no conflict of interest.