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. 2014 Jun 27:4:5478.
doi: 10.1038/srep05478.

Shape-controllable formation of poly-imidazolium salts for stable palladium N-heterocyclic carbene polymers

Huaixia Zhao  1 , Liuyi Li  1 , Yangxin Wang  1 , Ruihu Wang  1
Affiliations

Shape-controllable formation of poly-imidazolium salts for stable palladium N-heterocyclic carbene polymers

Huaixia Zhao et al. Sci Rep. .

Abstract

The imidazolium-based main-chain organic polymers are one of promising platforms in heterogeneous catalysis, the size and outer morphology of polymer particles are known to have important effects on their physical properties and catalytic applications, but main-chain ionic polymers usually generate amorphous or spherical particles. Herein, we presented a versatile and facile synthetic route for size- and shape-controllable synthesis of main-chain poly-imidazolium particles. The wire-shaped, spherical and ribbon-shaped morphologies of poly-imidazolium particles were readily synthesized through quaternization of bis-(imidazol-1-yl)methane and 2,4,6-tris(4-(bromomethyl)phenyl)-1,3,5-triazine, and the modification of their size and morphology were realized through adjusting solvent polarity, solubility, concentration and temperatures. The direct complexation of the particles with Pd(OAc)2 produced ionic polymers containing palladium N-heterocyclic carbene units (NHCs) with intactness of original morphologies. The particle morphologies have a significant effect on catalytic performances. Wire-shaped palladium-NHC polymer shows excellent catalytic activity and recyclabilty in heterogeneous Suzuki-Miyaura cross-coupling reaction.

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Conflict of interest statement

The authors declare no competing financial interests.

Figures

Figure 1
Figure 1. General synthetic route of PIS and PIS-Pd.
Figure 2
Figure 2
SEM images for (a) wire-shaped PIS1; (b) wire-shaped PIS1-Pd; (c) wire-shaped PIS1-Pd after catalytic cycle for 13 runs; (d) spherical PIS2; (e) spherical PIS2-Pd; (f) spherical PIS2-Pd after catalytic reaction; (g) ribbon-shaped PIS3; (h) ribbon-shaped PIS3-Pd; (i) ribbon-shaped PIS3-Pd after catalytic reaction.
Figure 3
Figure 3. SEM images for PIS formed at different conditions.
(a) 20 mL MeCN at 85°C; (b) 40 mL MeCN at 85°C; (c) 60 mL MeCN at 85°C; (d) 10 mL DMF at 85°C; (e) 5 mL DMF at 85°C; (f) 5 mL dioxane at 85°C.
Figure 4
Figure 4. Recyclability of wire-shaped PIS1-Pd in Suzuki-Miyaura cross-coupling reaction.
Reaction conditions: 4-bromoacetophenone (0.2 mmol), phenylboronic acid (0.3 mmol), base (0.4 mmol), PIS1-Pd (1 mol%) in H2O (1.0 mL) and DMF (0.5 mL) at 100°C for 3 h.
Figure 5
Figure 5. The plausible mechanism for PIS formation.
See this image and copyright information in PMC

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