Dinuclear Ruthenium Complexes Containing the Hpbl Ligand: Synthesis, Characterization, Linkage Isomerism, and Epoxidation Catalysis

Intramolecular Proton Transfer Boosts Water Oxidation Catalyzed by a Ru Complex

“…The redox properties of Ru–aqua species were analyzed based on CV experiments and are shown in Figure (right) at pH 8.2. A summary of the redox processes of Ru–aqua complexes is given in Scheme and can be easily rationalized following the reduction process starting from the most oxidized seven-coordinated species [Ru V (O)­(tda-κ-N 3 O)­(py) 2 ] + , 5 + , and keeping in mind that the geometry of the ligand tda 2– together with the different electronic nature of Ru­(II) and Ru­(III) fosters linkage isomerization processes. − Complex 5 + is responsible for the catalytic water oxidation reaction that will be described in the next section, and its formal V/IV redox couple at this pH is obtained by DPV ( E 1/2 4 = 1.43 V; Figure S20). The one-electron reduction of 5 + (Scheme ) generates [Ru IV (O)­(tda-κ-N 3 O)­(py) 2 ], 4 , that in turn can be further reduced by a one-electron process ( E 1/2 3 = 0.87 V) to generate [Ru III (OH)­(tda-κ-N 3 O)­(py) 2 ], 6 .…”

Alkene Epoxidation Catalysts [Ru(pdc)(tpy)] and [Ru(pdc)(pybox)] Revisited: Revealing a Unique RuIV═O Structure from a Dimethyl Sulfoxide Coordinating Complex

“…Ruthenium-based epoxidation catalysts have received much attention because of the well-developed Ru chemistry and the easy access of various redox states of Ru complexes. − In particular, Nishiyama et al reported the first use of [Ru­(pdc)­(tpy)] ( 1 ; H 2 pdc = 2,6-pyridyl dicarboxylic acid; tpy = 2,2′:6′,2″-terpyridine; Figure ) as an alkene-epoxidation catalyst in the presence of non-atom-economic oxidants such as PhI­(OAc) 2 , O 2 / t BuCHO, and t BuOOH . Later on, Beller and co-workers developed a series of catalysts of [Ru­(pdc)­(pybox)] (pybox = pyridine-bis­(oxazoline) ligands; complex 2 ; Figure ) that use hydrogen peroxide as the oxidant, with high activity and selectivity toward asymmetric epoxidation of alkenes. − The anionic ligand pdc 2– is essential to suppress the decomposition of hydrogen peroxide and to improve the efficiency of the Ru-pdc/H 2 O 2 system toward alkene epoxidation.…”

Electrochemically Driven Water Oxidation by a Highly Active Ruthenium‐Based Catalyst

“…The combination of 1 H NMR, 13 C NMR, 1 H‐ 1 H COSY, and HSQC experiments allowed for full assignment of the NMR spectra (Figure S13). The 1 H NMR spectrum of complex 4 III displayed broadened and shifted peaks, characteristic of a paramagnetic d 5 Ru III species (Figure S18) . Reduction of this Ru III complex to the Ru II state with ascorbic acid resulted in a 1 H NMR spectrum identical to that of complex 4 II (Figure S19).…”