New mononuclear ruthenium complexes with general formula [Ru(bid)(B)(Cl)] (bid is (1Z,3Z)-1,3-bis(pyridin-2-ylmethylene)isoindolin-2-ide; B = bidentate ligand 2,2'-bipyridine or R(2)-bpy, where R = COOEt or OMe) were synthesized and tested as precatalysts for the hydrogenative reduction of CO(2) in 2,2,2-trifluoroethanol (TFE) as solvent with added NEt(3). Significant amounts of formic acid were produced by these catalysts and a kinetic analysis based on initial rate constants was carried out. The potential mechanisms including intermediate species for these catalytic systems were investigated by means of quantum chemical calculations to gain deeper insight into the processes. The effect of electron-donating and electron-withdrawing groups on catalyst performance was studied both experimentally and theoretically.

The synthesis of new dinuclear complexes of the general formula {[Ru(II)(trpy)]2(μ-pdz-dc)(μ-(L)}(+) [pdz-dc is the pyridazine-3,6-dicarboxylate dianion; trpy is 2,2':6',2″-terpyridine; L = Cl (1(+)) or OH (2(+))] is described. These complexes are characterized by the usual analytical and spectroscopic techniques and by X-ray diffraction analysis. Their redox properties are characterized by means of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Complex 2(+) is used as the starting material to prepare the corresponding Ru-aqua complex {[Ru(II)(trpy)(H2O)]2(μ-pdz-dc)}(2+) (3(2+)), whose electrochemistry is also investigated by means of CV and DPV. Complex 3(2+) is able to catalytically and electrocatalytically oxidize water to dioxygen with moderate efficiencies. In sharp contrast, 3(2+) is a superb catalyst for the epoxidation of alkenes. For the particular case of cis-β-methylstyrene, the catalyst is capable of carrying out 1320 turnovers with a turnover frequency of 11.0 cycles min(-1), generating cis-β-methylstyrene oxide stereospecifically.

A series of mononuclear and dinuclear chiral manganese(II) complexes containing the neutral bidentate chiral nitrogen ligand (-)-pinene[5,6]bipyridine, (-)-L, were prepared from different manganese salts. The chirality in these complexes arises from the pinene ring that has been fused to the 5,6 positions of one pyridine group of the bipyridine ligand. These complexes have been characterized through analytical, spectroscopic (IR, UV/Vis, ESI-MS) and electrochemical techniques (cyclic voltammetry). Single X-ray structure analysis revealed a five-coordinated Mn(II) ion in [{MnCl((-)-L)}2(mu-Cl)2] (2), [{Mn((-)-L)}2(mu-OAc)3](PF6) (3) and [MnCl2(H2O)((-)-L)] (4) and a six-coordinated one in [MnCl2((-)-L)2] (5), [Mn(CF3SO3)2((-)-L)2] (6) and [Mn(NO3)(H2O)((-)-L)2)](NO3) (7). The magnetic properties of the binuclear compounds 2 and 3 have been studied. Both compounds show a weak antiferromagnetic coupling (2, J = -0.22 cm(-1); 3, J = -0.85 cm(-1)). The catalytic activity of the whole set of complexes has been tested with regard to the epoxidation of aromatic alkenes with peracetic acid. In the particular case of styrene, good selectivities and moderate enantioselectivities were obtained. Furthermore, total retention of the initial cis configuration was achieved when epoxidizing cis-beta-methylstyrene with the chloride complexes. In general, the epoxidation activity of these manganese complexes is strongly dependent on the steric encumbrance of the substrates employed.

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A family of new ruthenium complexes containing a combination of polypyridyl and carbene ligands has been prepared and characterized from structural, spectroscopic, and redox viewpoints both experimentally and computationally. Interestingly, a correlation between ΔE1/2, defined as the difference between E1/2(RuIV/III) and E1/2(RuIII/II), and the activity and selectivity of some catalytic oxidation processes has been clearly established. A density functional theory study on the synthesized species has been carried out revealing a correlation between the number of carbene ligands and ΔE1/2, and consequently with the RuIII disproportionation. The reactivity of these complexes has been tested with regard to the electrocatalytic oxidation of benzyl alcohol.