An Adaptive Rhodium Catalyst to Control the Hydrogenation Network of Nitroarenes.

An adaptive catalytic system that provides control over the nitroarene hydrogenation network to prepare a wide range of aniline and hydroxylamine derivatives is presented. This system takes advantage of a delicate interplay between a rhodium(III) center and a Lewis acidic borane introduced in the secondary coordination sphere of the metal. The high chemoselectivity of the catalyst in the presence of various potentially vulnerable functional groups and its readiness to be deployed at a preparative scale illustrate its practicality.

Acceptorless Dehydrogenation of Methanol to Carbon Monoxide and Hydrogen using Molecular Catalysts.

The acceptorless dehydrogenation of methanol to carbon monoxide and hydrogen was investigated using homogeneous molecular complexes. Complexes of ruthenium and manganese comprising the MACHO ligand framework showed promising activities for this reaction. The molecular ruthenium complex [RuH(CO)(BH )(HN(C H PPh ) )] (Ru-MACHO-BH) achieved up to 3150 turnovers for carbon monoxide and 9230 turnovers for hydrogen formation at 150 °C reaching pressures up to 12 bar when the decomposition was carried out in a closed vessel.

Controlling the Product Platform of Carbon Dioxide Reduction: Adaptive Catalytic Hydrosilylation of CO Using a Molecular Cobalt(II) Triazine Complex.

The catalytic reduction of carbon dioxide (CO ) is considered a major pillar of future sustainable energy systems and chemical industries based on renewable energy and raw materials. Typically, catalysts and catalytic systems are transforming CO preferentially or even exclusively to one of the possible reduction levels and are then optimized for this specific product. Here, we report a cobalt-based catalytic system that enables the adaptive and highly selective transformation of carbon dioxide individually to either the formic acid, the formaldehyde, or the methanol level, demonstrating the possibility of molecular control over the desired product platform.

Ruthenium-Catalyzed Urea Synthesis by N-H Activation of Amines.

Activation of the N-H bond of amines by a ruthenium pincer complex operating via "amine-amide" metal-ligand cooperation is demonstrated. Catalytic formyl C-H activation of N,N-dimethylformamide (DMF) is observed in situ, which resulted in the formation of CO and dimethylamine. The scope of this new mode of bond activation is extended to the synthesis of urea derivatives from amines using DMF as a carbon monoxide (CO) surrogate.

Ruthenium-catalysed multicomponent synthesis of borasiloxanes.

We present the selective atom economical synthesis of borasiloxanes using a multi-component approach directly by the one-pot ruthenium catalysed reaction of boranes, silanes and water.

Ruthenium-Catalyzed Selective Hydroboration of Nitriles and Imines.

Ruthenium-catalyzed hydroboration of nitriles and imines is attained using pinacolborane with unprecedented catalytic efficiency. Chemoselective hydroboration of nitriles over esters is also demonstrated. A simple [Ru(p-cymene)Cl] complex (1) is used as a catalyst precursor, which upon reaction with pinacolborane in situ generates the monohydrido-bridged complex [{(η-p-cymene)RuCl}(μ-H-μ-Cl)] 2.

Selective α-Deuteration of Amines and Amino Acids Using DO.

Monohydrido-bridged ruthenium complex [{(η-p-cymene)RuCl}(μ-H-μ-Cl)] catalyzes (catalyst load: 0.5-1 mol %) α-selective deuteration of primary and secondary amines, amino acids, and drug molecules using deuterium oxide (DO) as a deuterium source. Mechanistic investigations revealed N-H activation of amines, which was also established by single-crystal X-ray analysis of an intermediate.

Ruthenium-Catalyzed Regioselective 1,4-Hydroboration of Pyridines.

Simple ruthenium precursor [Ru(p-cymene)Cl2]2 1 catalyzed regioselective 1,4-dearomatization of pyridine derivatives using pinacolborane is reported. Two catalytic intermediates, [Ru(p-cymene)Cl2Py] 2 and [Ru(p-cymene)Cl2(P(Cy)3)] 3, involved in this process are identified, independently synthesized, characterized, and further used directly as effective catalysts; two more catalytic intermediates [Ru(p-cymene)Cl2(Py)(P(Cy)3)] 4 and [Ru(p-cymene)(H)Cl(Py)(P(Cy)3)] 5 are identified in solution. Complex 5 is the active catalytic intermediate.

The ruthenium-catalysed selective synthesis of mono-deuterated terminal alkynes.

We report an efficient catalytic method for the synthesis of mono-deuterated terminal alkynes directly from deuterium oxide, catalysed by a Ru(II) pincer complex in which the reaction proceeds via Ru-acetylide intermediates and amine-amide metal-ligand cooperation.

Ruthenium Catalyzed Selective α- and α,β-Deuteration of Alcohols Using D2O.

Highly selective ruthenium catalyzed α-deuteration of primary alcohols and α,β-deuteration of secondary alcohols are achieved using deuterium oxide (D2O) as a source of deuterium and reaction solvent. Minimal loading of catalyst (Ru-macho), base (KO(t)Bu), and low temperature heating provided efficient selective deuteration of alcohols making the process practically attractive and environmentally benign. Mechanistic studies indicate the D-O(D/R) bond activations by metal-ligand cooperation and intermediacy of carbonyl compounds resulting from dehydrogenation of alcohols.

Ruthenium Catalyzed Selective Hydroboration of Carbonyl Compounds.

Using the [Ru(p-cymene)Cl2]2 (1) complex, catalytic hydroboration of aldehydes and ketones with pinacolborane under neat and mild conditions is reported. At rt, chemoselective hydroboration of aldehydes over the ketones is also attained. Mechanistic studies confirmed the immediate formation of monohydride bridged dinuclear complex [{(η(6)-p-cymene)RuCl}2(μ-H-μ-Cl)] (1b) from the reaction of 1 with pinacolborane, which catalyzed the highly efficient hydroboration reactions.

Ruthenium catalyzed selective hydrosilylation of aldehydes.

A chemoselective hydrosilylation method for aldehydes is developed using a ruthenium catalyst [(Ru(p-cymene)Cl2)2] and triethylsilane; a mono hydride bridged dinuclear complex [{(η(6)-p-cymene)RuCl}2(μ-H-μ-Cl)] and a Ru(iv) mononuclear dihydride complex [(η(6)-p-cymene)Ru(H)2(SiEt3)2] are identified as potential intermediates in the reaction and the proposed catalytic cycle involves a 1,3-hydride migration.