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Ruthenium PNP pincer complexes bearing supplementary cyclometalated C,N‐bound ligands have been prepared and fully characterized for the first time. By replacing CO and H− as ancillary ligands in such complexes, additional electronic and steric modifications of this topical class of catalysts are possible. The advantages of the new catalysts are demonstrated in the general α‐alkylation of ketones with alcohols following a hydrogen autotransfer protocol. Herein, various aliphatic and benzylic alcohols were applied as green alkylating agents for ketones bearing aromatic, heteroaromatic or aliphatic substituents as well as cyclic ones. Mechanistic investigations revealed that during catalysis, Ru carboxylate complexes are predominantly formed whereas neither the PNP nor the CN ligand are released from the catalyst in significant amounts. [ABSTRACT FROM AUTHOR]

Complexes Ru(H)(Cl)(CO)(HN{CH2CH2P(iPr)2}2) 7 and Ru(H)(Cl)(CO)(CH3N{CH2CH2P(iPr)2}2) 8 were compared for the selective dehydrogenation (DH) of formic acid (FA) at different pH values. Remarkably, highest activities were observed in acidic environment (pH 4.5). Under all investigated conditions, the N‐methylated complex 8 showed improved performance compared to 7. These observations can be mechanistically explained with protonation of 4H/3Me being the key step in formic acid DH for both complexes. Pinch me! Comparing PNP−Ru pincer complexes with N‐methylated‐ and NH‐moieties demonstrated increased activity of the former complex. Remarkably, the highest activities were observed in acidic environment. [ABSTRACT FROM AUTHOR]

A series of seven novel NImNHP-type pincer imidazolylphosphine ruthenium complexes has been synthesized and fully characterized. The use of hydrogenation of benzonitrile as a benchmark test identified [RuHCl(CO)(NImNHP tBu)] as the most active catalyst. With its stable Ru−BH4 analogue, in which chloride is replaced by BH4, a broad range of (hetero)aromatic and aliphatic nitriles, including industrially interesting adiponitrile, has been hydrogenated under mild and base-free conditions. [ABSTRACT FROM AUTHOR]

The mechanism of acetonitrile and methyl benzoate catalytic hydrogenation using pincer catalysts M(H)2(CO)[NH(C2H4P iPr2)2] ( 1M) and M(H)(CO)[N(C2H4P iPr2)2] ( 2M) (M = Fe, Ru, Os) has been computed at various levels of density functional theory. The computed equilibrium between 1Fe and 2Fe agrees perfectly with the experimental observations. On the basis of the activation barriers and reaction energies, the best catalysts for acetonitrile hydrogenation are 1Fe/2Fe and 1Ru/2Ru, and the best catalysts for methyl benzoate hydrogenation are 1Ru/2Ru. The best catalysts for the dehydrogenation of benzyl alcohol are 1Ru/2Ru. It is to note that the current polarizable continuum model is not sufficient in modeling the solvation effect in the energetic properties of these catalysts as well as their catalytic properties in hydrogenation reaction, as no equilibrium could be established between 1Fe and 2Fe. Comparison with other methods and procedures has been made. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The Cover Feature shows how N‐Me Ru pincer complex "outweighs" its N‐H analogue in the hydrogen generation reaction from formic acid. In their Full Paper, A. Agapova et al. compared the reactivity of two ruthenium PNP catalysts for the dehydrogenation of formic acid at different pH values. Under all investigated conditions, the N‐methylated complex showed improved performance compared to non‐methylated one, and the highest TOF was observed in acidic environment. More information can be found in the Full Paper by A. Agapova et al. on page 1911 in Issue 7, 2019 (DOI: 10.1002/cctc.201801897). [ABSTRACT FROM AUTHOR]