Light‐Driven
<i>gem</i>
Hydrogenation: An Orthogonal Entry into “Second‐Generation” Ruthenium Carbene Catalysts for Olefin Metathesis
作者:Raphael J. Zachmann、Alois Fürstner
DOI:10.1002/chem.202101176
日期:2021.5.17
The newly discovered light‐driven gem hydrogenation of alkynes opens an unconventional yet efficient entry into five‐coordinate Grubbs‐type ruthenium carbene complexes with cis‐disposed chloride ligands. Representatives of this class featuring a chelate substructure formed by an iodo‐substituted benzylidene unit react with (substituted) 2‐isopropoxystyrene to give prototypical “second‐generation” Grubbs‐Hoveyda
A simple synthesis of [RuCl<sub>2</sub>(NHC)(<i>p</i>-cymene)] complexes and their use in olefin oxidation catalysis
作者:Xinyuan Ma、Sébastien G. Guillet、Min Peng、Kristof Van Hecke、Steven P. Nolan
DOI:10.1039/d1dt00030f
日期:——
A simple and efficient synthetic route to [RuCl2(NHC)(p-cymene)] and [Ru(CO3)(NHC)(p-cymene)] complexes making use of a weak base, under aerobic conditions, is reported. This method enables access to a series of NHC-ruthenium compounds with moderate to good yields under mild conditions. The Ru pre-catalysts were successfully used in olefin oxidation catalysis at lowcatalystloading and reach complete
An Anionic Dinuclear Ruthenium Dihydrogen Complex of Relevance for Alkyne
<i>gem</i>
‐Hydrogenation
作者:Tobias Biberger、Nils Nöthling、Markus Leutzsch、Christopher P. Gordon、Christophe Copéret、Alois Fürstner
DOI:10.1002/anie.202201311
日期:2022.6.13
Cationic and neutral non-classical σ-H2 complexes are plentiful, but anionic ones remain exceedingly rare. It was during an investigation into the fate of a Ru-precatalyst in the light-driven alkyne gem-hydrogenation that such a species was encountered, which seems to be “first-in-class”: it lacks any substructures that counteract the negative charge and prevent oxidative insertion of the metal centers
The ability of five imidazol(in)ium-2-carboxylates and dithiocarboxylates bearing cyclohexyl, mesityl, or 2,6-diisopropylphenyl substituents on their nitrogen atoms to act as NHC precursors for in situ catalytic applications was probed in ruthenium-promoted ring-opening metathesis and atom transfer radical polymerizations. Results obtained with 1:2 mixtures of [RuCl2(p-cymene)](2) and NHC center dot CO2 adducts were in line with those reported previously starting from preformed [RuCl2-(p-cymene)(NHC)] complexes, whereas the NHC center dot CS2 zwitterions were almost completely inactive. To account for this dichotomy, the preparation of preformed ruthenium-arene complexes from [RuCk(p-cymene)](2) and NHC center dot CX2 inner salts was thoroughly investigated. As expected, imidazolium-2-carboxylates lost their CO2 moiety and afforded [RuCl2(p-cyrnene)(NHC)] complexes in high yields, whereas the NHC center dot CS, betaines retained their zwitterionic nature and led to cationic complexes of the [RuCl(p-cymene)(NHC center dot CS2)]PF6 type. These stable, 18-electron species are the first examples of well-defined transition-metal complexes bearing chelating NHC center dot CS2 ligands. They were characterized by various analytical techniques, and the molecular structure of [RuCl(p-cymene)([Mes center dot CS2)]PF6 was determined by X-ray diffraction analysis.