Formation of exceptional monomeric YPhos-PdCl complexes with high activities in coupling reactions.

The use of well-defined palladium(ii) complexes as precatalysts for C-X cross-coupling reactions has improved the use of palladium catalysts in organic synthesis including large-scale processes. Whereas sophisticated Pd(ii) precursors have been developed in the past years to facilitate catalyst activation as well as the handling of systems with more advanced monophosphine ligands, we herein report that simple PdCl complexes function as efficient precatalysts for ylide-substituted phosphines (YPhos). These complexes are readily synthesized from PdCl sources and form unprecedented monomeric PdCl complexes without the need for any additional coligand.

Single and double deprotonation/dearomatization of the N,S-donor pyridinophane ligand in ruthenium complexes.

We report a series of ruthenium complexes with a tetradentate N,S-donor ligand, 2,11-dithia[3.3](2,6)pyridinophane (NS), that undergo single and double deprotonation in the presence of a base leading to the deprotonation of one or both pyridine rings. Both singly and doubly deprotonated complexes were structurally characterized by single-crystal X-ray diffraction.

Ylide-Substituted Phosphines: A Platform of Strong Donor Ligands for Gold Catalysis and Palladium-Catalyzed Coupling Reactions.

The development of homogeneous catalysts is strongly connected to the design of new, sophisticated ligands, which resolve limitations of a given reaction protocol by manipulating the electronic properties of the metal and its spatial environment. Phosphines are a privileged class of ligands that find applications in many catalytic transformations, ranging from hydrogenation reactions to hydroformylation and coupling chemistry. For many years, chemists have been trying to improve the efficiency, selectivity, and application of coupling reactions.

Phosphorus-ylides: powerful substituents for the stabilization of reactive main group compounds.

Phosphorus ylides are 1,2-dipolar compounds with a negative charge on the carbon atom. This charge is stabilized by the neighbouring onium moiety, but can also be shifted towards other substituents thus making ylides strong π donor ligands and hence ideal substituents to stabilize reactive compounds such as cations and low-valent main group species. Furthermore, the donor strength and the steric properties can easily be tuned to meet different requirements for stabilizing reactive compounds and for tailoring the properties and reactivities of the main group element.

Facile and reversible double dearomatization of pyridines in non-phosphine Mn complexes with N,S-donor pyridinophane ligand.

Single and double dearomatization of pyridine rings was observed in Mn complexes with an N2S2 pyridinophane ligand via deprotonation of one or two CH arms, respectively. In contrast to other N,S-donor pincer-like systems, the dearomatized (N2S2)Mn species were found to be stable, with the dearomatization being reversible.

Double Dehydrogenation of Primary Amines to Nitriles by a Ruthenium Complex Featuring Pyrazole Functionality.

A ruthenium(II) complex bearing a naphthyridine-functionalized pyrazole ligand catalyzes oxidant-free and acceptorless selective double dehydrogenation of primary amines to nitriles at moderate temperature. The role of the proton-responsive entity on the ligand scaffold is demonstrated by control experiments, including the use of a N-methylated pyrazole analogue. DFT calculations reveal intricate hydride and proton transfers to achieve the overall elimination of 2 equiv of H.

Hemilability-Driven Water Activation: A Ni Catalyst for Base-Free Hydration of Nitriles to Amides.

The Ni complex 1 containing pyridyl- and hydroxy-functionalized N-heterocyclic carbenes (NHCs) is synthesized and its catalytic utility for the selective nitrile hydration to the corresponding amide under base-free conditions is evaluated. The title compound exploits a hemilabile pyridyl unit to interact with a catalytically relevant water molecule through hydrogen-bonding and promotes a nucleophilic water attack to the nitrile. A wide variety of nitriles is hydrated to the corresponding amides including the pharmaceutical drugs rufinamide, Rifater, and piracetam.

A highly efficient catalyst for selective oxidative scission of olefins to aldehydes: abnormal-NHC-Ru(II) complex in oxidation chemistry.

The utility and selectivity of the catalyst [Ru(COD)(L(1))Br2] (1) bearing a fused π-conjugated imidazo[1,2-a][1,8]naphthyridine-based abnormal N-heterocyclic carbene ligand L(1) is demonstrated toward selective oxidation of C═C bonds to aldehydes and C≡C bonds to α-diketones in an EtOAc/CH3CN/H2O solvent mixture at room temperature using a wide range of substrates, including highly functionalized sugar- and amino acid-derived compounds.