CO Oxidation by N₂O Homogeneously Catalyzed by Ruthenium Hydride Pincer Complexes Indicating a New Mechanism

Abstract

Both CO and NO are important, environmentally harmful industrial gases. The reaction of CO and NO to produce CO and N has stimulated much research interest aimed at degradation of these two gases in a single step. Herein, we report an efficient CO oxidation by NO catalyzed by a (PNN)Ru-H pincer complex under mild conditions, even with no added base. The reaction is proposed to proceed through a sequence of O-atom transfer (OAT) from NO to the Ru-H bond to form a Ru-OH intermediate, followed by intramolecular OH attack on an adjacent CO ligand, forming CO and N. Thus, the Ru-H bond of the catalyst plays a central role in facilitating the OAT from NO to CO, providing an efficient and novel protocol for CO oxidation.

The Milstein Bipyridyl PNN Pincer Complex of Ruthenium Becomes a Noyori-Type Catalyst under Reducing Conditions

“…41 Two miscellaneous catalytic reactions of 11 via 2 involved CO oxidation by N 2 O and the selective deuteration of alcohols in D 2 O. 31,43 Reactions of Scheme 15 were proposed to proceed via the initial formation of an aromatized alkoxide complex from 2 and the substrate alcohol.…”

Identification of Active Sites and Structural Characterization of Reactive Ionic Intermediates by Cryogenic Ion Trap Vibrational Spectroscopy

“…[95] Ap rototypical example concernst he metal-mediated CO!CO 2 conversion which, arguably,i so ne of the most often studied system, both at surfaces [96] and in the gas phase. [52,97] [98,99] DFT calculations provided insight into the mechanism of the oxygen-atom transfers, Figure 2, and,i np articular,p redicted that it is the AlÀOa nd not the VÀOu nit of the heteronuclear [AlVO x ]C + clusterw hich, on both kinetica nd thermodynamic grounds, serves as the actives ite, Figure 2a nd Figure 3.…”

“…Both oxygen‐atom transfers are clean and proceed with reaction efficiencies of 59 and 65 %, relative to the collision rate, respectively. In principle, the turnover number (TON) of this ideal catalytic cycle (Scheme ) is infinite; however, in reality the TON is limited by side reactions with background impurities …”

Unexpected CNN-to-CC Ligand Rearrangement in Pincer–Ruthenium Precatalysts Leads to a Base-Free Catalyst for Ester Hydrogenation

“…Milstein and co-workers observed a CC-chelating binding mode when attempting complexation of their NHC–bipyridine ligand (see Chart ) with Ru­(PPh 3 ) 3 HCl­(CO) . The same group also observed rearrangement of a phosphine–bipyridine PNN–pincer ligand to a PNC-binding form on ruthenium …”

“…We identified these products as the CC-chelated complexes shown in Scheme 2, where the pyridine and amine nitrogen The same group also observed rearrangement of a phosphine− bipyridine PNN−pincer ligand to a PNC-binding form on ruthenium. 16 The solid-state structure of cis-Ru-dipp-Et-PPh 3 was determined by X-ray crystallography. Figure 1 shows the molecular structure.…”