Monometallic and bimetallic sulfonated Rh(I) complexes: Synthesis and evaluation as recyclable hydroformylation catalysts

The synthesis of two water-soluble Rh(I) complexes, a disulfonated diimine mononuclear complex and a tetrasulfonated tetraimine binuclear complex, is reported. The reaction of the N,N-donor ligands containing the sulfonated alkyl substituents with [Rh(COD)(MeCN)(2)]BF4 led to the formation of the corresponding water-soluble Rh(I) complexes. The complexes were fully characterised using an array of analytical techniques such as NMR, infrared spectroscopy and mass spectrometry. The complexes were evaluated as catalyst precursors in the aqueous biphasic hydroformylation of 1-octene. Both catalyst precursors are highly active as hydroformylation precatalysts showing high conversions of 1-octene and good aldehyde chemoselectivity with no hydrogenation products (alkanes or alcohols) observed. The binuclear complex gave higher quantitative conversions compared to the mononuclear rhodium complex. Additionally, the catalysts were recovered by phase separation and reused over four catalytic runs, notably with a significant drop in conversion after each cycle. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The synthesis of two water-soluble Rh(I) complexes and their performance as catalyst precursors in aqueous biphasic hydroformylation reaction were reported. Both catalyst precursors showed high activity and good selectivity, but experienced a decrease in conversion after multiple cycles.