Optically active amphiphilic hyperbranched polyglycerols as templates for palladium nanoparticles

We report a systematic study on the encapsulation of palladium nanoparticles in optically active amphiphilic hyperbranched polyglycerols with different optical signs and different degrees of polymerization, namely (−)-P(G40C160.5) 1 and (+)-P(G73C160.5) 2. Several issues have been addressed here: (a) relatively wide size distributions (1–5 nm) of palladium nanoparticles have been achieved, (b) a remarkable template effect (1, DPn = 40, 1.2 ± 0.1 nm; 2, DPn = 73, 2.3 ± 0.1 nm average particle size) has been observed using TEM technique, as shown by the particle size dependent on the degree of polymerization of the polymers, (c) NaBH4 is found to be a convenient reducing agent to produce small particle size compared with gaseous hydrogen, (d) catalytic Heck reaction of 2,3-dihydrofuran and aryl triflate has been tested successfully without enantiocontrol.

Palladium nanoparticles with relatively wide size distribution (1–5 nm) have been synthesized using optically active amphiphilic hyperbranched polyglycerols, (−)-P(G40C160.5) 1 and (+)-P(G73C160.5) 2 as polymeric templates. A remarkable template effect (1, DPn = 40, 1.2 ± 0.1 nm; 2 DPn = 73, 2.3 ± 0.1 nm average particle size) has been observed, as demonstrated by the particle size dependent on degree of polymerization of the polymers. The role of the reducing agents in the production of small particle size is presented as well as preliminary catalytic essay in a model catalytic Heck reaction.Figure optionsDownload as PowerPoint slide