The syntheses of cycloruthenated compounds by several methods, and especially by the C–H activation pathway, have been reviewed. Many ruthenium-containing starting materials lead to these interesting organometallic compounds, which have found various applications in different fields of chemistry. Their reactivity highlights both thevariety of reactions that were found to occur at the Ru–C bonds as well as the inertness of the organometallic moiety when these species are exposed to strongly oxidizing molecules or to reactive halogenation reagents. Their use as catalyst precursors showed them to be particularly efficient for hydrogenation reactions, either by H2 or by hydride transfer. Physicochemical characteristics of cycloruthenated complexes include: (i) a cathodic shift of the electrochemical potentials corresponding to various redox couples, (ii) a bathochromic shift of UV/Vis absorption bands, (iii) valuable luminescence properties. Dinuclear cycloruthenated complexes display specific properties connected to interactions between the metals, such as strong electronic coupling, evidenced by intervalence bands of mixed-valence species, or efficient energy transfer.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Cycloruthenated Compounds – Synthesis and Applications

In the present contribution, some novel Cu(II) complexes were synthesized from tri- and tetradentate imine ligands. All the prepared compounds were elucidated by different physicochemical methods. Density Functional Theory calculations were carried out to explain the equilibrium geometry of the bsisnph and npisnph ligands and their Cu(II) complexes. Interaction of the synthesized ligands with Cu(II) affords nano-sized particles via TEM. The catalytic potentials of the prepared complexes has been tested within the oxidation of benzyl alcohol using an environmental friendly terminal oxidant, i.e. H2O2. The effect of various parameters, e.g. solvents, temperature and amount of catalyst was investigated. A mechanistic pathway of the catalytic oxidation was tentatively described and discussed.

Some New Nano-sized Mononuclear Cu(II) Schiff Base Complexes: Design, Characterization, Molecular Modeling and Catalytic Potentials in Benzyl Alcohol Oxidation

A suitable method for the synthesis of ruthenium(II) arene benzhydrazone complexes (1–6) of the general formula [(η6-arene)Ru(L)Cl] (arene-benzene or p-cymene; L-monobasic bidentate substituted 9-anthraldehyde benzhydrazone derivatives) has been described. The composition of the complexes has been established by elemental analysis, IR, UV-Vis, emission, NMR and ESI-MS spectral methods. The solid state molecular structure of a representative complex was determined by a single-crystal X-ray diffraction study and indicates the presence of pseudo-octahedral (piano stool) geometry. All the complexes have been thoroughly screened for their cytotoxicity against human cervical cancer cells (HeLa), human breast cancer cell line (MDA-MB-231) and human liver carcinoma cells (Hep G2) under in vitro conditions. Interestingly, the cytotoxic activity of complex 6 is much more potent than cisplatin with low IC50 values against all the cancer cell lines tested. Furthermore, the results of AO–EB, Hoechst 33258 and flow cytometry analyses reveal that these complexes induce cell death only through apoptosis. The comet assay has been employed to determine the extent of DNA fragmentation in cancer cells. A hemolysis assay with human erythrocytes demonstrated good blood biocompatibility of all the ruthenium(II) arene benzhydrazone complexes. These results highlight the strong possibility to develop highly active ruthenium complexes as anticancer agents.

Ruthenium(II) arene complexes containing benzhydrazone ligands: synthesis, structure and antiproliferative activity

A series of colorful Salen-type Schiff bases derived from the different diamine bridges including 1,2-ethylenediamine (Et1–Et3), 1,2-cyclohexanediamine (Cy1–Cy3), 1,2-phenylenediamine (Ph1–Ph4), dicyano-1,2-ethenediamine (CN1–CN3), phenazine-2,3-diamine (Phen1–Phen3), and naphthalene-2,3-diamine (Naph1 and Naph2) have been designed and prepared. The presence of electron-accepting substituents, electron-donating substituents, donor–acceptor (DA) systems, and/or π-extended systems leads to not only full absorption and emission spectra (300–700 nm) in the visible region but also high fluorescence quantum yields up to 0.83 in solution. The experimental results and density functional theory (DFT) calculations have proved that the highest occupied molecular orbital (HOMO) levels, the lowest unoccupied molecular orbital (LUMO) levels, and consequently the energy gaps of these Salen ligands can be well tuned. The LUMO levels of these Salen ligands are mainly affected by the diamine bridges, whereas both the HOMO ...

Synthesis and Photophysical Properties of Colorful Salen-Type Schiff Bases

Organoselenium ligands are building blocks of several transition metal complexes which catalyze various organic reactions efficiently in solution. In this review the survey of developments pertaining to the designing of such complexes (along with their Se-ligands), and their uses as catalysts for various organic reactions has been presented with critical analysis of present status of the subject. Undoubtedly a new family of catalysts or their precursors has been generated by organoselenium ligands. The catalytic activity and selectivity of their metal complexes can sometimes be fine-tuned efficiently by changing the ligand's framework. They show good thermal and air-stability. This, coupled with ease in their handling and synthesis, may make them not only attractive but good alternatives to several popular catalysts.

Organoselenium ligands in catalysis.

Synthesis, luminescent, redox and catalytic properties of Ru(II) carbonyl complexes containing 2N2O donors

Ruthenium(III) complexes of amine-bis(phenolate) ligands as catalysts for transfer hydrogenation of ketones

Synthesis, characterization, redox property and biological activity of Ru(II) carbonyl complexes containing O,N-donor ligands and heterocyclic bases.

Half-sandwich para -cymene ruthenium(II) naphthylazophenolato complexes: Synthesis, molecular structure, light emission, redox behavior and catalytic oxidation properties

A simple and convenient synthesis of a new class of air-stable mononuclear cyclometallated ruthenium(II) carbonyl 2-(arylazo)phenolate complexes bearing triphenylarsine [Ru(ap-R)(AsPh 3 ) 2 (CO)] has been described. The 2-(arylazo)phenolate ligands behave as dianionic tridentate ligands and are coordinated to ruthenium through C, N and O by dissociation of the phenolic proton and the phenyl proton at the ortho position of the phenyl ring forming two five-membered chelate rings. These complexes have been characterized by elemental analysis, and FT-IR, 1 H NMR and UV–vis spectroscopies. In dichloromethane solution all the metal complexes exhibit characteristic metal-to-ligand charge transfer (MLCT) absorption and emission bands in the visible region. One of the complexes [Ru(ap-Cl)(AsPh 3 ) 2 (CO)] was successfully characterized by X-ray crystallography. Cyclic voltammetric data of all the complexes show Ru III /Ru II oxidation and Ru II /Ru I reduction within the range of +0.75 to +0.86 V and −0.50 to −0.57 V respect to Ag/AgCl, respectively. The potentials are observed with respect to the electronic nature of substituents (R) in the 2-(arylazo)phenolate ligands. Further, a complex ( 2 ) was tested as a new catalyst in the oxidation of primary and secondary alcohols in the presence of NMO as a more viable oxidant with moderate to high conversion. The formation of high valent Ru IV  = O species as a catalytic intermediate is proposed for the catalytic process.

K. Naresh Kumar

Papers

Synthesis, luminescent, redox and catalytic properties of Ru(II) carbonyl complexes containing 2N2O donors

Ruthenium(III) complexes of amine-bis(phenolate) ligands as catalysts for transfer hydrogenation of ketones

Synthesis, characterization, redox property and biological activity of Ru(II) carbonyl complexes containing O,N-donor ligands and heterocyclic bases.

Half-sandwich para -cymene ruthenium(II) naphthylazophenolato complexes: Synthesis, molecular structure, light emission, redox behavior and catalytic oxidation properties

Synthesis, structure and catalytic activity of cycloruthenated carbonyl complexes containing arylazo phenolate ligands