Synthesis and bonding analysis of pentagonal bipyramidal rhenium carboxamide oxo complexes

Seven-coordinate rhenium oxo complexes supported by a tetradentate bipyridine carboxamide/carboxamidate ligand are reported. The neutral dicarboxamide H2Phbpy-da ligand initially coordinates in an L4 (ONNO) fashion to an octahedral rhenium oxo precursor, yielding a seven-coordinate rhenium oxo complex. Subsequent deprotonation generates a new oxo complex featuring the dianionic (L2X2) carboxamidate (NNNN) form of the ligand. Computational studies provide insight into the relative stability of possible linkage isomers upon deprotonation. Structural studies and molecular orbital theory are employed to rationalize the relative isomer stability and provide insight into the rhenium-oxo bond order.

Crystallographic evidence for the stereoselective substitution of equatorial pyridyl ligands in ruthenium(III) complexes

Mononuclear Ru complexes catalyze dioxygen formation via water splitting; therefore, a detailed investigation into their water-oxidation process is necessary. In this study, we synthesized a series of Ru(III) complexes containing a dianionic tridentate ligand with three pyridine groups (one coordinated to Ru while the other two are "free") and investigated their substitution reactions in a water/acetonitrile mixture. Among the monodentate pyridyl ligands, the one at the equatorial position was crystallographically proven to be selectively substituted. Therefore, our results experimentally demonstrate the proposed coordination geometry for an intermediate during water oxidation over Ru complexes.

Carboxamide carbonyl-ruthenium(ii) complexes: detailed structural and mechanistic studies in the transfer hydrogenation of ketones

The organo-carboxamide carbonyl-ruthenium(ii) complexes displayed moderate catalytic activities in the transfer hydrogenation of a broad spectrum of ketones.

Bio-Inspired Molecular Catalysts for Water Oxidation

The catalytic tetranuclear manganese-calcium-oxo cluster in the photosynthetic reaction center, photosystem II, provides an excellent blueprint for light-driven water oxidation in nature. The water oxidation reaction has attracted intense interest due to its potential as a renewable, clean, and environmentally benign source of energy production. Inspired by the oxygen-evolving complex of photosystem II, a large of number of highly innovative synthetic bio-inspired molecular catalysts are being developed that incorporate relatively cheap and abundant metals such as Mn, Fe, Co, Ni, and Cu, as well as Ru and Ir, in their design. In this review, we briefly discuss the historic milestones that have been achieved in the development of transition metal catalysts and focus on a detailed description of recent progress in the field.

Mononuclear Ruthenium-Based Water Oxidation Catalyst Supported by Anionic, Redox-Non-Innocent Ligand: Heterometallic O-O Bond Formation via Radical Coupling Pathway

Cerium(IV)-driven water oxidation catalysis mediated by a mononuclear ruthenium(III) complex, [Ru(L)(pic)₃] (H₃L = 2,2'-iminodibenzoic acid, pic = 4-methylpyridine), has been demonstrated in this work. The mechanistic details of water oxidation have been investigated by the combined use of spectroscopy, electrochemistry, kinetic analysis, and computational studies. It was found that water oxidation proceeds via formal high-valent Ru^VII species. The capability of accessing such a high-valent state is derived from the non-innocent behavior of the anionic tridentate ligand frame which helps in accumulation of oxidative equivalents in cooperation with metal center. This metal-ligand cooperation facilitates the multi-electron-transfer reaction such as water oxidation. Kinetic analysis suggests water oxidation at a single site of Ru where O-O bond formation occurs via radical-radical coupling pathway between the oxygen atom of ruthenium-oxo species and the oxygen atom of the hydroxocerium(IV) ion.

Chemical and Photochemical Water Oxidation Mediated by an Efficient Single-Site Ruthenium Catalyst

Water oxidation is a fundamental step in artificial photosynthesis for solar fuels production. In this study, we report a single-site Ru-based water oxidation catalyst, housing a dicarboxylate-benzimidazole ligand, that mediates both chemical and light-driven oxidation of water efficiently under neutral conditions. The importance of the incorporation of the negatively charged ligand framework is manifested in the low redox potentials of the developed complex, which allows water oxidation to be driven by the mild one-electron oxidant [Ru(bpy)3 ]3+ (bpy=2,2'-bipyridine). Furthermore, combined experimental and DFT studies provide insight into the mechanistic details of the catalytic cycle.

On the mechanism of water oxidation catalyzed by a dinuclear ruthenium complex: a quantum chemical study

The development of efficient and robust catalysts for water oxidation is an essential element in solar water splitting. In the present paper, the reaction mechanism for a dinuclear Ru water oxidation catalyst has been investigated in detail through quantum chemical calculations.

The wonderful world of pyridine-2,6-dicarboxamide based scaffolds

This perspective focusses on a variety of scaffolds based on a pyridine-2,6-dicarboxamide fragment and their noteworthy roles in coordination chemistry, biomimetic studies, catalysis, and sensing.

Incorporation of a ruthenium–bis(pyridine)pyrazolate (Ru–bpp) water oxidation catalyst in a hexametallic macrocycle

New terpyridine-functionalised analogues of the in,in-[{Ru^II(trpy)}₂(μ-bpp)(H₂O)₂]³⁺ water oxidation catalyst (bpp = bis-(2-pyridyl)pyrazolate) have been synthesised and used to create a hexametallic {Fe₂Ru₄} macrocycle.

Water oxidation using earth-abundant transition metal catalysts: opportunities and challenges

Catalysts for the oxidation of water are a vital component of solar energy to fuel conversion technologies. This Perspective summarizes recent advances in the field of designing homogeneous water oxidation catalysts (WOCs) based on Mn, Fe, Co and Cu.

Catalyst–solvent interactions in a dinuclear Ru-based water oxidation catalyst

A new dinuclear ruthenium-based water oxidation catalyst is described. Insight is provided into interactions between the catalyst and acetonitrile, a common co-solvent in water oxidation catalysis.