Isomerization and Hydroformylation of Long-Chain Olefins Promoted by N^O Bidentate Rh(I) Catalysts Precursors Bearing Salicylaldimine and Naphthaldimine Supporting Ligands

A series of Schiff-base rhodium(I) complexes (C1–C8) chelating N^O salicylaldimine and naphthaldimine ligands have been synthesized and characterized. These complexes were evaluated for their ability to catalyse the isomerization and hydroformylation of terminal (1-octene and 1-decene) and internal olefins (1, 2-, 3-, and 4-octene) to linear and branched aldehydes. The pre-catalysts resulted in excellent substrate conversion (> 99%) with 100% chemoselectivity towards aldehydes, under mild conditions. Good regioselectivities towards branched aldehydes were observed from terminal and internal olefins, clearly demonstrating the catalysts' ability in thermodynamically favoured isomerization followed by hydroformylation (n/iso ratio ranging between 0.52 and 0.67).