Synthesis of Nanosheets Containing Uniformly Dispersed PdII Ions at an Aqueous/Aqueous Interface: Development of a Highly Active Nanosheet Catalyst for Mizoroki-Heck Reaction.

Abstract

A method was developed to synthesize a nanosheet at the interface of an aqueous layer of PdII ions and an aqueous layer of hydrophilic polymer bearing a metal coordination unit (HPMC). The nanosheet was synthesized through generation of an interface by the addition of an aqueous solution of PdII ions with a low specific gravity (1.03 g/cm3) to a dispersed aqueous solution of HPMC with a high specific gravity (1.50 g/cm3), resulting in rapid cross-linking at the interface. An electron probe microanalysis mapping image showed that the PdII ions were uniformly dispersed in the nanosheet. The nanosheet showed a high catalyst activity for the Mizoroki–Heck cross-coupling reaction with a turnover number (TON) and turnover frequency (TOF) greater than 3,333,333 and 138,889 h–1, respectively. These are the greatest TON and TOF values reported for heterogeneous polymeric catalysts for the Mizoroki–Heck reaction.