Hydroformylation activity of multinuclear rhodium complexes coordinated to dendritic iminopyridyl and iminophosphine scaffolds

The synthesis of poly(propyleneimine)-iminopyridyl and iminophosphine rhodium(I) metallodendrimers, with rhodium coordinated to monodentate (N-donor) and chelating, heterobidentate (P,N) moieties respectively located on the periphery, has been accomplished in order to evaluate their potential as hydroformylation catalysts. Related mononuclear complexes were obtained in a similar manner to model the multinuclear complexes. The multinuclear rhodium(I) complexes were found to be effective catalyst precursors in the hydroformylation of 1-octene, achieving higher conversions, faster reaction rates and slightly enhanced catalytic activity when compared with analogous mononuclear rhodium complexes. Hydroformylation reactions using the tetra- and octanuclear rhodium complexes generally show a chemoselective formation of aldehydes, together with a small amount of isomerisation products.

Graphical abstractFirst- and second-generation monodentate, iminopyridyl- and chelating, heterobidentate, iminophosphine rhodium(I) complexes based on a poly(propylene imine) dendritic scaffold were synthesized. The catalytic studies of the tetra- and octanuclear rhodium dendritic complexes, together with their mononuclear analogues, were evaluated as hydroformyaltion catalyst precursors using 1-octene as a model substrate.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Multinuclear rhodium complexes based on a poly(propyleneimine) dendritic scaffold have been developed. ► The rhodium complexes have been used in the hydroformylation reaction using 1-octene. ► The hydroformylation reactions show a chemoselective formation of aldehydes, together with a small amount of isomerisation products.