A New Mode of Operation of Pd-NHC Systems Studied in a Catalytic Mizoroki–Heck Reaction

A New Mode of Operation of Pd-NHC Systems Studied in a Catalytic Mizoroki–Heck Reaction Full article

Journal

Organometallics
ISSN: 1520-6041 , E-ISSN: 0276-7333

Output data

Year: 2017, Volume: 36, Number: 10, Pages: 1981-1992 Pages count : 12 DOI: 10.1021/acs.organomet.7b00184

Authors

Astakhov Alexander V. ¹ , Khazipov Oleg V. ¹ , Chernenko Andrey Yu. ¹ , Pasyukov Dmitry V. ¹ , Kashin Alexey S. ² , Gordeev Evgeniy G. ² , Khrustalev Victor N. ³ , Chernyshev Victor M. ¹ , Ananikov Valentine P. ^1,2

Affiliations

1	Platov South-Russian State Polytechnic University (NPI), Prosveschenya 132, Novocherkassk 346428, Russia
2	Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, Moscow 119991, Russia
3	Peoples' Friendship University of Russia (RUDN University), Miklukho-Maklay St. 6, Moscow 117198, Russia

Metal complexes bearing N-heterocyclic carbene (NHC) ligands are typically considered the system of choice for homogeneous catalysis with well-defined molecular active species due to their stable metal–ligand framework. A detailed study involving 19 different Pd-NHC complexes with imidazolium, benzimidazolium, and triazolium ligands has been carried out in the present work and revealed a new mode of operation of metal-NHC systems. The catalytic activity of the studied Pd-NHC systems is predominantly determined by the cleavage of the metal–NHC bond, while the catalyst performance is strongly affected by the stabilization of in situ formed metal clusters. In the present study, the formation of Pd nanoparticles was observed from a broad range of metal complexes with NHC ligands under standard Mizoroki–Heck reaction conditions. A mechanistic analysis revealed two different pathways to connect Pd-NHC complexes to “cocktail”-type catalysis: (i) reductive elimination from a Pd(II) intermediate and the release of NHC-containing byproducts and (ii) dissociation of NHC ligands from Pd intermediates. Metal-NHC systems are ubiquitously applied in modern organic synthesis and catalysis, while the new mode of operation revealed in the present study guides catalyst design and opens a variety of novel opportunities. As shown by experimental studies and theoretical calculations, metal clusters and nanoparticles can be readily formed from M-NHC complexes after formation of new M–C or M–H bonds followed by C–NHC or H–NHC coupling. Thus, a combination of a classical molecular mode of operation and a novel cocktail-type mode of operation, described in the present study, may be anticipated as an intrinsic feature of M-NHC catalytic systems.

Astakhov A.V. , Khazipov O.V. , Chernenko A.Y. , Pasyukov D.V. , Kashin A.S. , Gordeev E.G. , Khrustalev V.N. , Chernyshev V.M. , Ananikov V.P.
A New Mode of Operation of Pd-NHC Systems Studied in a Catalytic Mizoroki–Heck Reaction
Organometallics. 2017. V.36. N10. P.1981-1992. DOI: 10.1021/acs.organomet.7b00184 WOS Scopus OpenAlex

≡ Web of science:	WOS:000402019800012
≡ Scopus:	2-s2.0-85020425278
≡ OpenAlex:	W2605029271