Synthesis and studies of Rh(I) catalysts within and across poly(alkyl aryl ether) dendrimers

In order to study the efficiencies of catalytic moieties within and across dendrimer generations, partially and fully functionalized dendrimers were synthesized. Poly(alkyl aryl ether) dendrimers from zero to three generations, presenting 3 to 24 peripheral functionalities, were utilized to prepare as many as 12 catalysts. The dendrimer peripheries were partially and fully functionalized with triphenylphosphine in the first instance. A rhodium(I) metal complexation was performed subsequently to afford multivalent dendritic catalysts, both within and across generations. Upon synthesis, the dendritic catalysts were tested in the hydrogenation of styrene, in a substrate-to-catalyst ratio of 1:0.001. Turn-over-numbers were evaluated for each catalyst, from which significant increases in the catalytic activities were identified for multivalent catalysts than monovalent catalysts, both within and across generations.

Graphical abstractPoly(alkyl aryl ether) dendrimers from zero to three generations, presenting 3 to 24 peripheral functionalities, were utilized to prepare as many as 12 Rh(I)-incorporated dendritic catalysts, both within and across generations. The dendritic catalysts were evaluated in the case of a hydrogenation reaction. Fully or mostly functionalized dendritic catalysts exhibited significantly increased catalytic efficiencies, as opposed to dendrimers incorporated with lesser number of catalytic moieties. The observations reiterate roles of dendrimer generations, number of catalytic moieties and resulting catalytic efficiencies.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► Multivalent dendritic catalysts using poly(alkyl aryl ether) dendrimer are prepared. ► Twelve different Rh(I) catalysts with-in 1 to 3 generations are prepared. ► Multivalent catalysts show increased catalysis in catalytic hydrogenation reactions. ► Marked differences in catalysis are seen for the mono- and multivalent catalysts.