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

A series of rhodium(I)-1,2,3-triazol-5-ylidene (trz) complexes are described, containing either a novel triarylated trz ligand A' (N1, N3-arylated, C4-ferrocenyl) {complexes 1, [Rh(A') Cl(cod)]; 4, [Rh(A') Cl(CO) 2]}, or N3-alkylated triazolylidenes with a C4-ferrocenyl {2, [Rh(B') Cl(cod)]; 5, [Rh(B') Cl(CO) 2]} or C4-phenyl substituent {3, [Rh(C') Cl(cod)]; 6, [Rh(C') Cl(CO) 2]}. The free mesoionic carbene (MIC) A' is structurally characterized and its electronic properties evaluated by employing the complex [Pd(Br) 2(iPr2-bimy)(A')] (7) in an NMR spectroscopic analysis method. The redox activity of A' is exploited, and the chemically oxidized precursor Aox and complex 4ox are isolated. The mesoionic carbene complexes 1-3, as well as in situ oxidized 1ox, are used as homogeneous catalysts for the hydroformylation of 1-octene for the first time, and the influence of chemical oxidation of the catalyst on the activity and chemoand regioselectivity of the catalyst precursor 1 is evaluated.