Improving the Catalytic Activity in the Rhodium-Mediated Hydroformylation of Styrene by a Bis(N-heterocyclic silylene) Ligand

Marcel Schmidt, Burgert Blom, Tibor Szilvasi, Reinhard Schomäcker*, Matthias Driess*

*Corresponding author for this work

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Abstract

For the first time, a significant boost in catalytic activity in the rhodium-catalysed hydroformylation of an alkene by using a bidentate bis(N-heterocyclic silylene) ligand is reported. This is shown by the hydroformylation of styrene at 30 bar CO/H-2 pressure in the presence of [HRh(CO)(PPh3)(3)] with an excess of the ferrocenediyl-based bis-NHSi ligand 4, [({eta 5-C5H4{ PhC(NtBu)(2)} Si})(2)Fe], which results in superior catalytic activity, compared with the bidentate diphosphines DPPF (3a) and xantphos (3b). In contrast, the hydroformylation of styrene in the presence of [HRh(CO)(PPh3) 3] with excesses of the monodentate NHSi ligands [{PhC(NtBu)(2)} SiNMe2] (1) and [{C2H2(NtBu)(2)} Si:] (2) at 30 bar CO/H-2 pressure revealed consid-erably slower conversion to the aldehyde products than [HRh(CO)(PPh3)(3)], with or without an excess of PPh3, showing catalyst deactivation. Surprisingly, the germanium analogue of 4 is shown to be virtually catalytically inactive. The superior activity of 4, compared with the xantphos-containing benchmark system, is rationalized on the basis of solution NMR spectroscopic studies, and the comparative catalyst cycles are elucidated using density functional theory (DFT) methods. The latter quantum-chemical studies explain very well the favourable energy pathway for the hydroformylation of styrene using 4 versus xantphos.

Original languageEnglish
Pages (from-to)1284-1291
Number of pages8
JournalEuropean Journal of Inorganic Chemistry
Issue number9
DOIs
Publication statusPublished - 3 Mar 2017

Keywords

  • GAUSSIAN-BASIS SETS
  • BITE ANGLE
  • COORDINATION CHEMISTRY
  • STABLE SILYLENES
  • LOW-PRESSURE
  • COMPLEXES
  • TRIPHENYLPHOSPHINE
  • OLEFINS
  • SYSTEM
  • RH

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