Cooperative catalysis by iridium complexes with a bipyridonate ligand: versatile dehydrogenative oxidation of alcohols and reversible dehydrogenation-hydrogenation between 2-propanol and acetone

Oxidation catalysis in air with Cp*Ir: influence of added ligands and reaction conditions on catalytic activity and stability

The systematic evaluation of Ir catalysts generates the highest reported TONs and a safe protocol for air oxidation.

Silver nanoparticles supported on silica-coated ferrite as magnetic and reusable catalysts for oxidant-free alcohol dehydrogenation

The oxidant-free dehydrogenation of alcohols to corresponding carbonyl compounds has been performed by using silver (0) nanoparticles supported on silica-coated ferrite as an efficient and recyclable heterogeneous catalyst.

From a decomposition product to an efficient and versatile catalyst: the [Ru(η5-indenyl)(PPh3)2Cl] story

One of the most important challenges in catalyst design is the synthesis of stable promoters without compromising their activity. For this reason, it is important to understand the factors leading to decomposition of such catalysts, especially if side-products negatively affect the activity and selectivity of the starting complex. In this context, the understanding of termination and decomposition processes in olefin metathesis is receiving significant attention from the scientific community. For example, the decomposition of ruthenium olefin metathesis precatalysts in alcohol solutions can occur during either the catalyst synthesis or the metathesis process, and such decomposition has been found to be common for Grubbs-type precatalysts. These decomposition products are usually hydridocarbonyl complexes, which are well-known to be active in several transformations such as hydrogenation, terminal alkene isomerization, and C-H activation chemistry. The reactivity of these side products can be unwanted, and it is therefore important to understand how to avoid them and maybe also important to keep an open mind and think of ways to use these in other catalytic reactions. A showcase of these decomposition studies is reported in this Account. These reports analyze the stability of ruthenium phenylindenylidene complexes, highly active olefin metathesis precatalysts, in basic alcohol solutions. Several different decomposition processes can occur under these conditions depending on the starting complex and the alcohol used. These indenylidene-bearing metathesis complexes display a completely different behavior compared with that of other metathesis precatalysts and show an alternative competitive alcoholysis pathway, where rather than forming the expected hydrido carbonyl complexes, the indenylidene fragment is transformed into a η(1)-indenyl, which then rearranges to its η(5)-indenyl form. In particular, [RuCl(η(5)-(3-phenylindenylidene)(PPh3)2] has been found to be extremely active in numerous transformations (at least 20) as well as compatible with a broad range of reaction conditions, rendering it a versatile catalytic tool. It should be stated that the η(5)-phenyl indenyl ligand shows enhanced catalytic activity over related half-sandwich ruthenium complexes. The analogous half-sandwich (cyclopentadienyl and indenyl) ruthenium complexes show lower activity in transfer hydrogenation and allylic alcohol isomerization reactions. In addition, this catalyst allows access to new phenylindenyl ruthenium complexes, which can be achieved in a very straightforward manner and have been successfully used in catalysis. This Account provides an overview of how mechanistic insights into decomposition and stability of a well-known family of ruthenium metathesis precatalysts has resulted in a series of novel and versatile ruthenium complexes with unexpected reactivity.

Effective dehydrogenation of 2-pyridylmethanol derivatives catalyzed by an iron complex

Effective dehydrogenation of 2-pyridylmethanol derivatives was achieved using an iron catalyst (TON = 67 000) without a hydrogen acceptor.

2-Hydroxy-1,10-phenanthroline vs 1,10-phenanthroline: significant ligand acceleration effects in the palladium-catalyzed oxidative Heck reaction of arenes

A series of bidentate monoanionic nitrogen ligands were designed and applied in the Pd-catalyzed oxidative Heck reaction of arenes with alkenes. Significant ligand-accelerated effects were observed, and direct C-H functionalized products were formed in high yields with meta-selectivity.

Conversion of carbohydrate biomass to γ-valerolactone by using water-soluble and reusable iridium complexes in acidic aqueous media

Mild-mannered manipulation: A catalytic method for the conversion of carbohydrate biomass to γ-valerolactone in acidic aqueous media has been developed. The water-soluble iridium complexes were observed to be extremely catalytically active for providing γ-valerolactone in high yields with high TONs. The homogeneous catalysts can also be recycled and reused by applying a simple phase separation process.