A triarylated 1,2,3-triazol-5-ylidene ligand with a redox-active ferrocenyl substituent for rhodium(I)-catalyzed hydroformylation of 1-octene

Abstract

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 chemo- and regioselectivity of the catalyst precursor 1 is evaluated.