A comparative computationally study about the defined m(II) pincer hydrogenation catalysts (m = fe, ru, os)

Abstract

The mechanism of acetonitrile and methyl benzoate catalytic hydrogenation using pincer catalysts M(H)2 (CO)[NH(C2 H4 PiPr2 )2 ] (1M) and M(H)(CO)[N(C2 H4 PiPr2 )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.

Benyzl Alcohol Dehydrogenative Coupling Catalyzed by Defined Mn and Re PNP Pincer Complexes – A Computational Mechanistic Study

“…Since both water and methanol have been reported to lower the barriers of catalyst regeneration, we explored such effect of PhCH 2 OH as proton shuttle for the interconversion between 1M and 2M in gas phase and in PhCH 2 OH. A two‐step mechanism corresponding to proton transfer from PhCH 2 OH to the nitrogen atom of the ligand as well as H–H cleavage was located.…”

“…Indeed, B3PW91 has been used successfully in other metal based pincer complexes. [29a], All structures were optimized at the B3PW91 level with the TZVP basis set (LANL2DZ for Mn and Re). All optimized structures were characterized either as energy minimums without imaginary frequencies or transition states with only one imaginary mode by frequency calculations; and the transition state connects the initial and the final states.…”

Hydrogenation of Aliphatic and Aromatic Nitriles Using a Defined Ruthenium PNP Pincer Catalyst

“…In the final step, intermediate B forms amine C, while 9 is regenerated by the addition of H 2 to 10. In our recent computational work, [16] we found that ruthenium complex 9Ј (isopropyl instead of phenyl) should also catalyze the nitrile hydrogenation by the same outersphere reaction mechanism.…”

Inexpensive Ruthenium NNS‐Complexes as Efficient Ester Hydrogenation Catalysts with High C=O vs. C=C Selectivities

“…Presumably, complex C1 b is activated through metal‐ligand‐cooperation, which is typical for pincer complexes bearing an amine functionality and/or a benzylic position which can be deprotonated . This could lead to the ruthenium diyhdride species C1 b‐H (Scheme ).…”