Phosphinous Acid-Assisted Hydration of Nitriles: Understanding the Controversial Reactivity of Osmium and Ruthenium Catalysts.

Title Phosphinous Acid-Assisted Hydration of Nitriles: Understanding the Controversial Reactivity of Osmium and Ruthenium Catalysts.
Authors R. González-Fernández; P. Crochet; V. Cadierno; I. Menéndez; R. López
Journal Chemistry
DOI 10.1002/chem.201703481
Abstract

The synthesis and catalytic behaviour of the osmium(II) complexes [OsCl2(?6-p-cymene)(PR2OH)] [R = Me (2a), Ph (2b), OMe (2c), OPh (2d)] in nitrile hydration reactions is presented. Among them, the best catalytic results were obtained with the phosphinous acid derivative [OsCl2(?6-p-cymene)(PMe2OH)] (2a), which selectively provided the desired primary amides in excellent yields and short times at 80 ºC, employing directly water as solvent, and without the assistance of any basic additive (TOF values up to 200 h-1). The process was operative with both aromatic, heteroaromatic, aliphatic, and ?,?-unsaturated organonitriles and showed a high functional group tolerance. Indeed, complex 2a represents the most active and general osmium-based catalyst for the hydration of nitriles reported so far in the literature. In addition, it exhibits a catalytic performance similar to that of its ruthenium analogue [RuCl2(?6-p-cymene)(PMe2OH)] (4). However, when compared to 4, the osmium complex 2a turned out to be faster in the hydration of the less reactive aliphatic nitriles, while the opposite trend was in general observed with the aromatic substrates. DFT computations suggest that these differences in reactivity are mainly related to the ring strain associated to the key intermediate in the catalytic cycle, i.e. a five-membered metallacyclic species generated by intramolecular addition of the hydroxyl group of the phosphinous acid ligand to the metal-coordinated nitrile.

Citation R. González-Fernández; P. Crochet; V. Cadierno; I. Menéndez; R. López.Phosphinous Acid-Assisted Hydration of Nitriles: Understanding the Controversial Reactivity of Osmium and Ruthenium Catalysts.. Chemistry. 2017. doi:10.1002/chem.201703481

Related Elements

Osmium

76 Os 190.230000000 Osmium

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Ruthenium

44 Ru 101.070000000 Ruthenium

See more Ruthenium products. Ruthenium (atomic symbol: Ru, atomic number: 44) is a Block D, Group 8, Period 5 element with an atomic weight of 101.07. Ruthenium Bohr ModelThe number of electrons in each of ruthenium's shells is [2, 8, 18, 15, 1] and its electron configuration is [Kr] 4d7 5s1. The ruthenium atom has a radius of 134 pm and a Van der Waals radius of 207 pm. Ruthenium was discovered by Jędrzej Śniadecki in 1807. It was first recognized as a distinct element by Karl Ernst Claus in 1844. Elemental RutheniumIn its elemental form, ruthenium has a silvery white metallic appearance. Ruthenium is a rare transition metal belonging to the platinum group of metals. It is found in pentlandite, pyroxenite, and platinum group metal ores. The name Ruthenium originates from the Latin word "Ruthenia," meaning Russia.

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