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. 2019 Aug 16;12(16):2612.
doi: 10.3390/ma12162612.

Mesoporous Palladium N,N'-Bis(3-Allylsalicylidene)o-Phenylenediamine-Methyl Acrylate Resins as Heterogeneous Catalysts for the Heck Coupling Reaction

Claudio Mella  1 , Cecilia C Torres  2 , Gina Pecchi  1   3 , Cristian H Campos  4
Affiliations

Mesoporous Palladium N,N'-Bis(3-Allylsalicylidene)o-Phenylenediamine-Methyl Acrylate Resins as Heterogeneous Catalysts for the Heck Coupling Reaction

Claudio Mella et al. Materials (Basel). .

Abstract

Palladium N,N'-bis(3-allylsalicylidene)o-phenylenediamine complex (PdAS) immobilized onto mesoporous polymeric methyl acrylate (MA) based resins (PdAS(x)-MA, x = 1, 2, 5, or 10 wt.%) were successfully prepared as heterogeneous catalysts for the Heck reaction. The catalysts were synthesized via radical suspension polymerization using PdAS as a metal chelate monomer, divinylbenzene and MA as co-monomers. The effect of the PdAS(x) content on the physicochemical properties of the resins is also reported. The catalysts were characterized by using a range of analytical techniques. The large surface area (>580 m2·g-1) and thermal stability (up to 250 °C) of the PdAS(x)-MA materials allows their application as catalysts in the C-C coupling reaction between iodobenzene and MA in the presence of trimethylamine at 120 °C using DMF as the solvent. The PdAS(10)-MA catalyst exhibited the highest catalytic performance with no significant catalytic loss being observed after five reuses, thereby indicating excellent catalyst stability in the reaction medium.

Keywords: metal chelate monomer; palladium coordinated polymer; porous polymer.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Scheme 2
Scheme 2
Proposed mechanism of the Heck reaction. (a) Mechanism for Pd(II)/Pd(0) adapted from [66] and (b) mechanism for tetradentate Pd(II) catalyst adapted from palladium(II)-porphyrin complex [71] as model homogeneous catalyst.
Scheme 2
Scheme 2
Proposed mechanism of the Heck reaction. (a) Mechanism for Pd(II)/Pd(0) adapted from [66] and (b) mechanism for tetradentate Pd(II) catalyst adapted from palladium(II)-porphyrin complex [71] as model homogeneous catalyst.
Figure 1
Figure 1
Thermogravimetric profiles of PdAS(x)-MA catalysts. (a) PdAS(1)-MA, (b) PdAS(2)-MA, (c) PdAS(5)-MA, and (d) PdAS(10)-MA.
Figure 2
Figure 2
SEM energy-dispersive X-ray spectroscopy (SEM-EDS) micrographs analysis. (a) Pd-AS(1)-MA (b) Pd-AS(2)-MA (c) Pd-AS(5)-MA, and (d) Pd-AS(10)-MA.
Figure 3
Figure 3
N2 adsorption-desorption isotherm at –196 °C for the PdAS(x)-MA catalysts. (a) Pd-AS(1)-MA, (b) Pd-AS(2)-MA, (c) Pd-AS(5)-MA, and (d) Pd-AS(10)-MA.
Figure 4
Figure 4
CP/MAS 13C NMR spectra of PdAS(x)-MA catalysts.
Figure 5
Figure 5
DRS UV–vis spectra for the PdAS(x)-MA catalysts.
Figure 6
Figure 6
Survey XPS spectrum of the PdAS complex and PdAs(x)-MA catalysts (Pd 3d region; inset). Lines, PdAS complex (black), PdAS(1)-MA (red), PdAS(2)-MA (blue), PdAS(5)-MA (magenta) and PdAS(10)-MA (green).
Figure 7
Figure 7
Kinetic profiles for the coupling of I-Ph with methyl acrylate to produce methyl cinnamate (MCIN) using the Pd-based catalysts. (a) Open square: Pd(CH3CO2)2; open triangle: Pd-SALOPHEN, fill circle: PdAS(1)-MA, fill diamond: PdAS(2)-MA, fill pentagon: PdAS(5)-MA, and fill inverse triangle: PdAS(10)-MA. (b) Hg(0) poisoning test for Pd-SALOPHEN catalyst and (c) Hg(0) poisoning test for Pd(CH3CO2)2 catalyst.
Scheme 1
Scheme 1
The Heck cross-coupling for I-Ph and MA to produce MCIN.
Figure 8
Figure 8
TEM micrographs for the used Pd-based catalysts. (a) Pd(CH3CO2)2), (b) Pd-SALOPHEN, (c) PdAS(1)-MA, (d) PdAS(2)-MA, (e) PdAS(5)-MA and (f) PdAS(10)-MA.
Figure 8
Figure 8
TEM micrographs for the used Pd-based catalysts. (a) Pd(CH3CO2)2), (b) Pd-SALOPHEN, (c) PdAS(1)-MA, (d) PdAS(2)-MA, (e) PdAS(5)-MA and (f) PdAS(10)-MA.
Figure 9
Figure 9
Recycle and hot filtration study for PdAS(10)-MA catalyst in the production of MCIN at 120 °C using DMF as solvent. (a) Recycles, (b) hot filtration test for the first cycle, and (c) hot filtration test for the fifth cycle.
Figure 10
Figure 10
Physicochemical characterization of PdAS(10)-MA used catalyst. (a) TEM micrographs for PdAS(10)-MA catalyst after third reaction cycle, (b) TEM micrographs for PdAS(10)-MA catalyst after fifth reaction cycle, and (c) XRD diffraction pattern for the fresh catalyst, after third and fifth reaction cycle (● Metallic Pd (JCPDS 65-2867)).
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