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 language | English |
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Pages (from-to) | 1284-1291 |
Number of pages | 8 |
Journal | European Journal of Inorganic Chemistry |
Issue number | 9 |
DOIs | |
Publication status | Published - 3 Mar 2017 |
Keywords
- GAUSSIAN-BASIS SETS
- BITE ANGLE
- COORDINATION CHEMISTRY
- STABLE SILYLENES
- LOW-PRESSURE
- COMPLEXES
- TRIPHENYLPHOSPHINE
- OLEFINS
- SYSTEM
- RH