A Convoluted Polymeric Imidazole Palladium Catalyst: Structural Elucidation and Investigation of the Driving Force for the Efficient Mizoroki-Heck Reaction

• Published in: ChemCatChem Vol. 7; no. 14; pp. 2141 - 2148
• Main Authors: Sato, Takuma, Ohno, Aya, Sarkar, Shaheen M., Uozumi, Yasuhiro, Yamada, Yoichi M. A.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 13.07.2015; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: EXAFS spectroscopy; Mizoroki-Heck reaction; nanostructures; palladium; structure elucidation
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.201500249

MPPI‐Pd (7 mol ppm Pd), prepared from poly(N‐isopropylacrylamide‐co‐N‐vinylimidazole) and (NH4)2PdCl4 by our molecular convolution method, promoted the Mizoroki–Heck reaction in water to give the corresponding coupling products with high yield and reusability. To clarify why the catalyst was so active, structural elucidation and temperature‐dependent absorption/discharge investigation were performed using X‐ray absorption fine structure analysis, Raman and far‐IR spectroscopy, elemental analysis, and DFT calculations, which provided the structure of cis‐PdCl2L2 (L=imidazole moiety). Moreover, the temperature‐dependent absorption and discharge of aryl iodides and water in MPPI‐Pd were observed with near‐IR spectroscopy and macroscopic observations. The efficient diffusion of organic substrates into the internal nanospaces in MPPI‐Pd and the following discharge of the water molecules at 80 °C should enhance the catalytic activity dramatically as the driving force of the reaction. Pd polymer provides products: MPPI‐Pd, prepared from poly(N‐isopropylacrylamide‐co‐N‐vinylimidazole) and (NH4)2PdCl4 by our molecular convolution method, promotes the Mizoroki–Heck reaction in water to give the corresponding coupling products with high yield and reusability.