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An in situ generated catalyst from readily available RuH(2)(PPh(3))(4), an N-heterocyclic carbene (NHC) precursor, NaH, and acetonitrile was developed. The catalyst showed high activity for the amide synthesis directly from either alcohols or aldehydes with amines. When a mixture of an alcohol and an aldehyde was reacted with an amine, both of the corresponding amides were obtained with good yields. Homogeneous Ru(0) complexes such as (eta(4)-1,5-cyclooctadiene)(eta(6)-1,3,5-cyclooctatriene)ruthenium [Ru(cod)(cot)] and Ru(3)(CO)(12) were also active in the amidation of an alcohol or an aldehyde with the help of an in situ generated NHC ligand.

Acceptorless dehydrogenative oxidation of primary amines into nitriles using an in situ complex derived from commercially available dichloro(1,5-cyclooctadiene) ruthenium(II) complex and simple hexamethylenetetramine has been demonstrated. The synthetic protocol is highly selective and yields the nitrile compounds in moderate to excellent yields and produces hydrogen as the sole byproduct. [ABSTRACT FROM AUTHOR]

An efficient, operatively simple, acceptorless, and base-free dehydrogenation of secondary alcohols and nitrogen-containing heterocyclic compounds was achieved by using readily available ruthenium hydride complexes as precatalysts. The complex RuH2(CO)(PPh3)3 ( 1) and Shvo's complex ( 2) showed excellent activities for the dehydrogenation of secondary alcohols and nitrogen containing heterocycles. In addition to complexes 1 and 2, the complex RuH2(PPh3)4 ( 3) also showed moderate to excellent activity for the acceptorless dehydrogenation of nitrogen-containing heterocyclic compounds. Kinetic studies on the oxidation reaction of 1-phenylethanol using complex 1 were carried out in the presence and the absence of external triphenylphosphine (PPh3). External addition of PPh3 had a negative influence on the rate of the reaction, which suggested that dissociation of PPh3 occurred during the course of the reaction. Hydrogen was evolved from the oxidation reaction of 1-phenylethanol by using 1 mol% of 1 (88%) and 2 (92%), which demonstrated the possible usage of the catalytic systems in hydrogen generation. [ABSTRACT FROM AUTHOR]

• Dehydrogenation of Animes and Alcohols using simple RuCl 3 ·nH 2 O. • Hydrogen is only by-product and no acceptor is used. • Nitriles, imines and ketones are produced in excellent yields. A highly efficient, economic and environmental friendly catalyst system has been developed for the dehydrogenation of alcohols and amines using simple RuCl 3 ·nH 2 O and N - benzylhexamethylenetetramine. The in situ catalyst system efficiently oxidized the primary and secondary amines and secondary alcohols into nitrile, imine and ketone products, respectively in moderate to excellent yields. The developed catalyst system was also found to be efficient for the dehydrogenation of N -heterocyles. A detailed mechanism study revealed the first example of N - benzylhexamethylenetetramine (HMTA-Bz) being simultaneously acting as base, reducing agent and hydride source to generate the [Ru(II)(H) 2 species as the active catalyst. The mechanism studies also revealed both the alcohol and amine oxidation involves dehydrogenative pathway with the evolution of hydrogen as the only by-product. The developed catalyst system also provides possible platform for the release of hydrogen from liquid organic hydrogen carriers (LOHCs). [ABSTRACT FROM AUTHOR]

[Display omitted] A ruthenium hexamethylenetetramine complex [RuCl 2 (p -cym)HMTA] was prepared in quantitative yield at room temperature for 30 m. NMR and fluorescence spectroscopic studies revealed that the complex is unstable in solution resulting in the decomposition of HMTA unit with the elimination of p -cymene moiety. The newly synthesized complex is very efficient for the conversion of amines and alcohols into imines and ketones, respectively, in the absence of any base/additive/acceptor. The synthetic viabilty of the catalyst was successfully tested for the gram scale synthesis of industrially important product bis(4-chlorophenyl)methanone. The spectroscopic and experimental studies showed that ruthenium-hydride species was formed as active catalyst during the catalytic reactions and oxidation of alcohols and amines follows a dehydrogenative oxidation mechanism. The amount of hydrogen gas evolved during the ruthenium complex catalysed oxidation of diphenylmethanol was estimated to be 92%, implies the potential usage of catalyst in the field of liquid organic hydrogen storage. [ABSTRACT FROM AUTHOR]

A very efficient, highly atom economical and environmentally benign oxidation of secondary alcohols using three different in situ catalyst systems has been demonstrated. All the three catalyst systems were generated from commercially available ruthenium(II)benzenedichloride dimer, dicholro(1,5-cyclooctadiene)ruthenium(II) polymer and ruthenium(II)(p -cymene)dichloride dimer in combination with simple, cheap and eco-friendly hexamethylenetetramine as the additive. Moreover, all the catalyst systems were found to be highly atom economic as they avoid the employment of any stoichiometric hydrogen acceptor. Among all the three catalyst systems, ruthenium(II)(p -cymene)dichloride dimer was found to be very active with a low catalyst loading of 0.5 mol% and a maximum turn over number (TON) of 700 was obtained while using 0.1 mol% of ruthenium(II)(p -cymene)dichloride dimer. Experimental results have shown that the oxidation of alcohols involves dehydrogenative pathway and produces hydrogen as the sole product and suggesting the use of the developed catalyst systems for the release of hydrogen from liquid organic hydrogen carriers. 1H-NMR studies on ruthenium(II)(p -cymene)dichloride dimer system proved that the reaction involves formation of ruthenium-hydride species as the active catalyst. [Display omitted] [ABSTRACT FROM AUTHOR]