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-<br>sulfonatosalicylaldimine have been synthesised via sulfonation and Schiff base condensation reactions.<br>The ligand (3) and the new water-soluble mononuclear 5-sulfonatosalicylaldimine-ferrocenylimine<br>complexes (4 and 5) have been synthesised and characterised fully using 1H NMR, 13C{1H} NMR, and FTIR<br>spectroscopy, elemental analysis as well as mass spectrometry. Subsequently, the Rh(I) heterobimetallic<br>complexes (6 and 7) were synthesised from [RhCl(COD)]2 (COD ¼ 1,5-cyclooctadiene) and the<br>ferrocenylimine metalloligands (4 and 5) and characterised using various analytical and spectroscopic<br>techniques. These complexes were applied as catalyst precursors in aqueous biphasic hydroformylation<br>reactions. Optimal conditions were established at 95 ?C (40 bar), showing the best chemoselectivity for<br>aldehydes. The mononuclear ferrocenyl pre-catalysts (4 and 5) were inactive in the aqueous-biphasic<br>hydroformylation of 1-octene. The heterobimetallic catalyst precursors (6 and 7) displayed good activity<br>and could be recycled for at least 4 runs under the investigated conditions for the aqueous biphasic<br>hydroformylation of 1-octene.