Synthesis, Structure, and Reactivity of the Methoxy-Bridged Dimer [Cp∧Ru(μ-OMe)]2(Cp∧= η5-1-Methoxy-2,4-di-tert-butyl-3-neopentylcyclopentadienyl)

Synthesis of a diruthenium μ-η4-α-diimine complex via dehydrogenative coupling of cyclic amines and its role in dehydrogenative oxidation of pyrrolidine

The reaction of [Cp‡Ru(μ-H)4RuCp‡] (1: Cp‡ = 1,2,4-tri-tert-butylcyclopentadienyl) with cyclic amines at 180 °C afforded a μ-η4-α-diimine complex, [(Cp‡Ru)2(μ-η4-C2nH4n-4N2)] (5a-c: n = 4, 5, 6), via dehydrogenative coupling of two cyclic amine molecules. An intermediate μ-η2-1-pyrroline complex, [{Cp‡Ru(μ-H)}2(μ-η2-C4H7N)] (2a), was synthesized by the photoreaction of 1 with pyrrolidine and 5a was shown to be formed via the disproportionation of 2a upon thermolysis yielding 1 and a μ-imidoyl complex, [(Cp‡Ru)2(μ-η2:η2-C4H6N)(μ-H)] (3a). Complex 3a was transformed into 5avia the incorporation of 1-pyrroline, which was formed by the reaction of 2a with H2. DFT calculations on the model complexes supported by C5H5 groups at the B3LYP level suggested that the μ-η4-α-diimine ligand is formed via the insertion of a terminal cyclic aminocarbene ligand into the Ru-C bond of the μ-imidoyl group followed by the elimination of hydrogen. Although 5a was inert under an Ar atmosphere, it catalyzed the dehydrogenative oxidation of pyrrolidine under an atmosphere of hydrogen to yield γ-butyrolactam. An active species possessing a terminal cyclic aminocarbene ligand was generated via the heterolytic activation of hydrogen at the Ru-N bond followed by C-C bond cleavage.

The Fascinating Chemistry of α-Haloamides

The aim of this review is to highlight the rich chemistry of α-haloamides originally mainly used to discover new C-N, C-O and C-S bond forming reactions, and later widely employed in C-C cross-coupling reactions with C(sp3), C(sp2) and C(sp) coupling partners. Radical-mediated transformations of α-haloamides bearing a suitable located unsaturated bond has proven to be a straightforward alternative to access diverse cyclic compounds by means of either radical initiators, transition metal redox catalysis or visible light photoredox catalysis. On the other hand, cycloadditions with α-halohydroxamate-based azaoxyallyl cations have garnered significant attention. Moreover, in view of the important role in life and materials science of difluoroalkylated compounds, a wide range of catalysts has been developed for the efficient incorporation of difluoroacetamido moieties into activated as well as unactivated substrates.

Base-Free Dynamic Kinetic Resolution of Secondary Alcohols with a Ruthenium-Lipase Couple

We report the dynamic kinetic resolution (DKR) of various secondary alcohols by the combination of a ruthenium catalyst and an anionic surfactant-activated lipoprotein lipase. The DKR reactions performed under totally base-free conditions at room temperature provided the products of excellent enantiopurities (91-99% ee or greater) in high yields (92-99%). More importantly, the DKR of α-arylallyl alcohols was achieved for the first time with high yields (87-91%).

Exploring the Ruthenium-Ligands Bond and Their Relative Properties at Different Computational Methods

We report some experimental bond distances and computational models of six ruthenium bonds obtained from DFT to higher computational methods like MP2 and CCSD. The bonds distances, geometrical RMSD, and the thermodynamic properties of the models from different computational methods are similar. It is observed that optimization of molecules of many light atoms with different functional methods results in significant geometrical variation in the values and order of the computed properties. The values of the hyperpolarizabilities, HOMO, LUMO, and isotropic and anisotropic shielding are found to depend greatly on the type of the functional used and the geometrical variation rather than on the nature of basis set used. However, all the methods rated modelled Ru-S, Ru-Cl, and Ru-O bonds as having the highest hyperpolarizabilities values. The infrared spectra data obtained from the different computational methods are significantly different from each other except for MP2 and CCSD which are found to be very similar.

Development of ruthenium-based complexes as anticancer agents: toward a rational design of alternative receptor targets

In the search for novel anticancer agents, the development of metal-based complexes that could serve as alternatives to cisplatin and its derivatives has received considerable attention in recent years. This becomes necessary because, at present, cisplatin and its derivatives are the only coordination complexes being used as anticancer agents in spite of inherent serious side effects and their limitation against metastasized platinum-resistant cancer cells. Although many metal ions have been considered as possible alternatives to cisplatin, the most promising are ruthenium (Ru) complexes and two Ru compounds, KP1019 and NAMI-A, which are currently in phase II clinical trials. The major obstacle against the rational design of these compounds is the fact that their mode of action in relation to their therapeutic activities and selectivity is not fully understood. There is an urgent need to develop novel metal-based anticancer agents, especially Ru-based compounds, with known mechanism of actions, probable targets, and pharmacodynamic activity. In this paper, we review the current efforts in developing metal-based anticancer agents based on promising Ru complexes and the development of compounds targeting receptors and then examine the future prospects.

Theoretical study of the electronic and spectroscopic properties of some Ru(II) anticancer complexes

DFT method has been applied to study the thermodynamic and spectroscopic properties of three Ru-based complexes. Possible reasons for the reported experimental stability of complexes 1 and 2 with bidentate chelating ligands over complex 3 have been explained using computed properties. The results show that the trend in their thermodynamic, hyperpolarizabilities, magnetizabilities and the NMR isotropic shielding agree well with many of their experimental properties which give further detail explanation to the reported differences in their stability, hydrolysis and anticancer activities. We also found out that these complexes which were originally designed as anticancer agents have high hyperpolarizabilities which suggest that they can also act as good non-linear optical (NLO) materials.

Insights into the Intramolecular Properties ofη6-Arene-Ru-Based Anticancer Complexes Using Quantum Calculations

The factors that determine the stability and the effects of noncovalent interaction on theη6-arene ruthenium anticancer complexes are determined using DFT method. The intramolecular and intra-atomic properties were computed for two models of these half-sandwich ruthenium anticancer complexes and their respective hydrated forms. The results showed that the stability of these complexes depends largely on the network of hydrogen bonds (HB), strong nature of charge transfer, polarizability, and electrostatic energies that exist within the complexes. The hydrogen bonds strength was found to be related to the reported anticancer activities and the activation of the complexes by hydration. The metal–ligand bonds were found to be closed shell systems that are characterised by high positive Laplacian values of electron density. Two of the complexes are found to be predominantly characterised by LMCT while the other two are predominately characterised by MLCT.

Radicals in transition metal catalyzed reactions? transition metal catalyzed radical reactions? - a fruitful interplay anyway: part 2. Radical catalysis by group 8 and 9 elements

This review summarizes the current status of transition metal catalyzed reactions involving radical intermediates in organic chemistry. This part focuses on radical-based methods catalyzed by group 8 and group 9 metal complexes. Reductive and redox-neutral coupling methods catalyzed by low-valent metal complexes as well as catalytic oxidative C-C bond formations are reviewed.