Synthesis, characterisation and reactivity of water-soluble ferrocenylimine-Rh(I) complexes as aqueous-biphasic hydroformylation catalyst precursors

Water-soluble complexes based on monosodium 5-sulfonato salicylaldimine (3) and 3-tbutyl-5-sulfonatosalicylaldimine have been synthesised via sulfonation and Schiff base condensation reactions.The ligand (3) and the new water-soluble mononuclear 5-sulfonatosalicylaldimine-ferrocenyliminecomplexes (4 and 5) have been synthesised and characterised fully using 1H NMR, 13C{1H} NMR, and FTIRspectroscopy, elemental analysis as well as mass spectrometry. Subsequently, the Rh(I) heterobimetalliccomplexes (6 and 7) were synthesised from [RhCl(COD)]2 (COD ¼ 1,5-cyclooctadiene) and theferrocenylimine metalloligands (4 and 5) and characterised using various analytical and spectroscopictechniques. These complexes were applied as catalyst precursors in aqueous biphasic hydroformylationreactions. Optimal conditions were established at 95 ?C (40 bar), showing the best chemoselectivity foraldehydes. The mononuclear ferrocenyl pre-catalysts (4 and 5) were inactive in the aqueous-biphasichydroformylation of 1-octene. The heterobimetallic catalyst precursors (6 and 7) displayed good activityand could be recycled for at least 4 runs under the investigated conditions for the aqueous biphasichydroformylation of 1-octene.