Rhodium(I) Ferrocenylcarbene Complexes: Synthesis, Structural Determination, Electrochemistry, and Application as Hydroformylation Catalyst Precursors

Abstract

n Pr] were prepared, and the electronic effects of co-ligands and alkoxy vs. aminocarbene substituents were investigated by spectroscopic and electrochemical methods. The molecular structures of complexes 1, 2 and 4-6 were confirmed by single crystal X-ray diffraction. The use of the complexes 1-8 as homogeneous catalysts for the hydroformylation of 1-octene was demonstrated, and the influence of the carbene substituents and co-ligands on the activity and regioselectivity of the catalysis evaluated. Finally, the stability of the Rh-Ccarbene bond of complex 1 under hydroformylation conditions was confirmed with 13 C NMR experiments.

Gold(ii) in redox-switchable gold(i) catalysis

“…Compared to Fc-MICs with redox-active Fc substituents in a  position relative to the carbene donor, the Fc moiety in 1 located in the  position might have an even larger impact on the ligand's donor properties. Furthermore, the redox potentials for the Fc/Fc + oxidation of :C(Fc)OEt and Fc-MICs are very different, 28,42 opening the possibility of different valence isomers for cationic gold complexes [AuCl(Fc-MIC)] + and 1 + and consequently a different reactivity. For comparison of [AuCl(Fc-MIC)] 0/+ and 1 0/+ , we studied the gold catalysed cyclisation of N(2-propyn-1-yl)benzamide to 2-phenyl-5-vinylidene-2oxazoline (Scheme 1).…”

“…27,28 The neutral carbene ligand :C(Fc)OEt already possesses a similar donor strength (TEP = 2054 cm -1 ) as the oxidised Fc-MICs. 27,28,42 Consequently, the oxidised carbene ligand [:C(Fc)OEt] + should have an even lower donor ability and could enable high catalytic activity with AuCl[C(Fc)OEt] 1 as precatalyst (Scheme 1).…”

A Triarylated 1,2,3‐Triazol‐5‐ylidene Ligand with a Redox‐Active Ferrocenyl Substituent for Rhodium(I)‐Catalyzed Hydroformylation of 1‐Octene

“…For the hydroformylation of olefins, numerous examples of rhodium(I)‐based catalysts with a ferrocenyl ligand substituent have been reported; however, the effect of the redox activity of these ferrocenyl substituents on the performance of the catalysts remains unexplored. Similarly, we have recently reported the syntheses of a range of rhodium(I)–ferrocenyl–Fischer‐carbene catalyst precursors for the hydroformylation of 1‐octene . In an effort to maintain sufficient electron density on the rhodium(I) centre for maximum conversion of the terminal olefins, whereby the linear aldehydes are the preferred hydroformylation product for most applications, an increase in the n/iso ratio of the product aldehydes were targeted by modifying the electrophilic π‐acceptor carbene ligands with an electron‐donating ferrocenyl substituent .…”

Synthesis and Reactivity of Phosphine-Quinolinolato Rhodium Complexes: Intermediacy of Vinylidene and (Amino)carbene Complexes in the Catalytic Hydroamination of Terminal Alkynes

“…While several rhodium­(I) complexes bearing N–C carbene –C-type (amino)­carbene ligands including ylide-stabilized carbene ligands have been prepared, − only one report includes the preparation of rhodium­(I) complexes possessing an (alkyl)­(amino)­carbene ligand . In the paper on the synthesis of the first stable (alkyl)­(amino)­carbene, C­( t Bu)­(N i Pr 2 ), by Bertrand and co-workers in 2004, they also reported on the synthesis of (alkyl)­(amino)­carbene rhodium­(I) complexes using the carbene itself as a ligand source.…”