An anionic, chelating C(sp 3 ) / NHC ligand from the combination of N-heterobicyclic carbene and barbituric heterocycle - Archive ouverte HAL Access content directly
Journal Articles Organometallics Year : 2021

An anionic, chelating C(sp 3 ) / NHC ligand from the combination of N-heterobicyclic carbene and barbituric heterocycle

Abstract

The coordination chemistry of the anionic NHC 1– based on an imidazo[1,5-a]pyridin-3-ylidene (IPy) platform substituted at the C5 position by an anionic barbituric heterocycle was studied with d6 (Ru(II), Mn(I)) and d8 (Pd(II), Rh(I), Ir(I), Au(III)) transition-metal centers. While the anionic barbituric heterocycle is planar in the zwitterionic NHC precursor 1·H, NMR spectroscopic analyses supplemented by X-ray diffraction studies evidenced the chelating behavior of ligand 1– through the carbenic and the malonic carbon atoms in all of the complexes, resulting from a deformation of the lateral barbituric heterocycle. The complexes were obtained by reaction of the free carbene with the appropriate metal precursor, except for the Au(III) complex 10, which was obtained by oxidation of the antecedent gold(I) complex [AuCl(1)]− with PhICl2 as an external oxidant. During the course of the process, the kinetic gold(I) intermediate 9 resulting from the oxidation of the malonic carbon of the barbituric moiety was isolated upon crystallization from the reaction mixture. The νCO stretching frequencies recorded for complex [Rh(1)(CO)2] (5) demonstrated the strong donating character of the malonate-C(sp3)/NHC ligand 1–. The ruthenium complex [Ru(1)Cl(p-cymene)] (11) was implemented as a precatalyst in the dehydrogenative synthesis of carboxylic acid derivatives from primary alcohols and exhibited high activities at low catalyst loadings (25–250 ppm) and a large tolerance toward functional groups.
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Dates and versions

hal-03356487 , version 1 (28-09-2021)

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Idir Benaissa, Katarzyna Gajda, Laure Vendier, Noël Lugan, Anna Kajetanowicz, et al.. An anionic, chelating C(sp 3 ) / NHC ligand from the combination of N-heterobicyclic carbene and barbituric heterocycle. Organometallics, 2021, 40 (18), pp.3223-3234. ⟨10.1021/acs.organomet.1c00458⟩. ⟨hal-03356487⟩
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