Octahedral Ruthenium Research Articles

Synthesis, structural characterization and catalytic transfer hydrogenation of ruthenium(II) carbonyl complexes bearing N,N,O pincer type benzoylhydrazone ligands

The convenient synthesis of four new octahedral ruthenium(II) carbonyl benzoylhydrazone complexes of the general molecular formula [Ru(L)Cl(CO)(PPh3)] (where HL=substituted 2-acetylpyridine benzoylhydrazones; the H represents the dissociable proton) has been described. The characterization of the complexes was accomplished by spectroscopic (FT-IR, 1H NMR, UV–Vis) techniques as well as by elemental (C,H,N) analysis. A single crystal X-ray diffraction study of a representative complex, [Ru(L1)Cl(CO)(PPh3)] (1), confirms a pincer-like N,N,O coordination mode of the benzoylhydrazone ligand via the pyridine N, the azomethine N and the deprotonated amide O atoms, with the formation of two five-membered fused chelate rings, and indicates a distorted octahedral geometry around the ruthenium(II) centre. Further, the catalytic efficiency of complex 1 has been investigated for the transfer hydrogenation of substituted acetophenones to the corresponding secondary alcohols. The influence of base and catalyst loading in the transfer hydrogenation reaction was also evaluated. The complexes were found to be efficient catalysts in the presence of iso-propanol/KOH with conversions up to 99.2%.

Construction of pincer-type symmetrical ruthenium(ii) complexes bearing pyridyl-2,6-pyrazolyl arms: catalytic behavior in transfer hydrogenation of ketones

Convenient synthesis of four new distorted octahedral ruthenium(II) complexes (1, 2, 3, 4) having general molecular formula [RuCl2LPAr3] (L = pyridine-based tridentate ligands not containing N–H bonds) is described. Their composition and structure were determined by elemental analysis and NMR spectra, and complexes 2 and 4 were also identified by X-ray single-crystal diffraction. All ruthenium(II) complexes exhibited good to excellent catalytic activity in the transfer hydrogenation of ketones. Among them, complex 4 achieved the highest final TOF value of 51 600 h−1 for a high molar ratio of substrate to catalyst (2000 : 1).

Interactions of octahedral ruthenium(II) polypyridyl complexes with the RNA triplex poly(U)•poly(A)*poly(U) effect on the third-strand stabilization.

Stable triplexes play key roles in many biological processes. Due to the Hoogsteen base pairing, triplexes are, however, thermodynamically less stable than the corresponding duplexes. The poor stabilization of these structures limits their practical applications under physiological conditions. To understand the factors effect on the stabilization of RNA triplexes by octahedral ruthenium(II) complexes, the interactions of [RuL2(uip)](2+) {where L = 2,2'-bipyridine (bpy) or 1,10-phenanthroline phen, uip = 2-(5-uracil)-1H-imidazo[4,5-f][1,10]phenanthroline} with the RNA triplex poly(U)•poly(A)*poly(U) are examined by spectrophotometry, spectrofluorometry, circular dichroism, and viscosimetry in this work. The main results obtained here suggest that the third-strand stabilization depends on the hydrophobicity effects of ancillary ligands bpy and phen.

Direct Synthesis of Amides from Coupling of Alcohols and Amines Catalyzed by Ruthenium(II) Thiocarboxamide Complexes under Aerobic Conditions

Four octahedral ruthenium(II) thiocarboxamide complexes of the general formula [RuClCO(AsPh3)2(L)] (L = N-substituted pyridine-2-thiocarboxamide) incorporating carbonyl and triphenylarsine have been synthesized from the reaction of 1 equiv of ruthenium precursor [RuHClCO(AsPh3)3] with 1 equiv of thiocarboxamide ligands in refluxing ethanol in the presence of base. All the new complexes have been fully characterized by means of elemental analysis, IR, UV–vis, and NMR spectral methods. Molecular structures of all the complexes were determined by X-ray crystallography, which confirm the coordination mode of thiocarboxamide and reveal the presence of a distorted octahedral geometry around the Ru ion. All the ruthenium(II) thiocarboxamide complexes were generated as highly efficient catalysts for synthesis of secondary or tertiary amides by coupling of amines and alcohols with low catalyst loading, and the maximum yield was obtained up to 97%. The coupling reaction can be readily carried out under mild aerobic conditions, and release of water is the only byproduct. Further, the effect of substituents of the ligand, solvents, reaction temperature, time, and catalyst loading on the catalytic activity of the complexes has been investigated. A plausible mechanism is proposed for the synthesis of amides via hemiaminal as intermediate through an oxidation of an alcohol to aldehyde.

Ruthenium(II) bipyridine complexes bearing quinoline–azoimine (NN′N″) tridentate ligands: Synthesis, spectral characterization, electrochemical properties and single-crystal X-ray structure analysis

Four octahedral ruthenium(II) azoimine–quinoline complexes having the general molecular formula [RuII(LY)(bpy)Cl](PF6) {LY=YC6H4NNC(COCH3)NC9H6N, Y=H (1), CH3 (2), Br (3), NO2 (4) and bpy=2,2′-bipyrdine} were synthesized. The azoimine–quinoline based ligands behave as NN′N″ tridentate donors and coordinated to ruthenium via azo-N′, imine-N′ and quinolone-N″ nitrogen atoms. The composition of the complexes has been established by elemental analysis, spectral methods (FT-IR, electronic, 1H NMR, UV/Vis and electrochemical (cyclic voltammetry) techniques. The crystal structure of complex 1 is reported. The Ru(II) oxidation state is greatly stabilized by the novel tridentate ligands, showing Ru(III/II) couples ranging from 0.93–1.27V vs. Cp2Fe/Cp2Fe+. The absorption spectrum of 1 in dichloromethane was modeled by time-dependent density functional theory (TD-DFT).

Synthesis, characterization, DNA interaction, antioxidant and anticancer activity of new ruthenium(II) complexes of thiosemicarbazone/semicarbazone bearing 9,10-phenanthrenequinone

A new series of octahedral ruthenium(II) complexes supported by tridentate ligands derived from phenanthrenequinone and derivatives of thiosemicarbazide/semicarbazide and other co-ligands have been synthesized and characterized. DNA binding experiments indicated that ruthenium(II) complexes can interact with DNA through non-intercalation and the apparent binding constant value (Kb) of [RuCl(CO)(PPh3)(L3)] (3) at room temperature was calculated to be 2.27×103M−1. The DNA cleavage studies showed that the complexes have better cleavage of pBR 322 DNA. Antioxidative activity proved that the complexes have significant radical scavenging activity against free radicals. Cytotoxic activities showed that the ruthenium(II) complexes exhibited more effective cytotoxic activity against selected cancer cells.

Active Cross‐Linkers that Lead to Active Gels

Chemomechanical reaction: The first octahedral ruthenium bipyridine complex that bears six polymerizable vinyl groups is used as an active cross-linker. It is a key building block for cross-linked polymeric networks (right) thus allowing the construction of molecular architectures in chemomechanical soft materials.

Ruthenium(II) carbonyl complexes bearing quinoline-based NNO tridentate ligands as catalyst for one-pot conversion of aldehydes to amides and o-allylation of phenols

Six new octahedral ruthenium(II) carbonyl complexes having the general molecular formula [RuCl(CO)(B)L1–2] (B=PPh3, AsPh3 or py; L1–2=quinoline based NNO ligand) were synthesized. The quinoline based ligands behave as monoanionic tridentate donor and coordinated to ruthenium via ketoenolate oxygen, azomethine nitrogen and quinoline nitrogen. The composition of the complexes has been established by elemental analysis and spectral methods (FT-IR, electronic, 1H NMR, 13C NMR, 31P NMR and ESI-Mass). The complexes were used as efficient catalysts for one-pot conversion of various aldehydes to their corresponding primary amides in presence of NH2OH·HCl and NaHCO3. The effect of catalyst loading and reaction temperature on catalytic activity of the ruthenium(II) carbonyl complexes were also investigated. The synthesized complexes also possess good catalytic activity for the o-allylation of phenols in the presence of K2CO3 under mild conditions. The complexes afforded branched allyl aryl ethers according to a regioselective reaction.

Self‐Assembly of Ambidentate Pyridyl‐Carboxylate Ligands with Octahedral Ruthenium Metal Centers: Self‐Selection for a Single‐Linkage Isomer and Anticancer‐Potency Studies

The synthesis of six new [2+2] metallarectangles through the coordination-driven self-assembly of octahedral Ru(II)-based acceptors with ambidentate pyridyl-carboxylate donors is described. These molecular rectangles are fully characterized by (1)H NMR spectroscopy, high-resolution electrospray mass spectrometry, and single-crystal X-ray diffraction. In each case, despite the possible formation of multiple isomers, based on the relative orientation of the pyridyl and carboxylate groups (head-to-head versus head-to-tail), evidence for the formation of a single preferred ensemble (head-to-tail) was found in the (1)H NMR spectra. Furthermore, the cytotoxicities of all of the rectangles were established against A549 (lung), AGS (gastric), HCT-15 (colon), and SK hep 1 (liver) human cancer cell lines. The cytotoxicities of rectangles that contained the 5,8-dihydroxy-1,4-naphthaquinonato bridging moiety between the Ru centers (9-11) were particularly high against AGS cancer cells, with IC50 values that were comparable to that of reference drug cisplatin.

Bimetallic Octahedral Ruthenium–Nickel Carbido Cluster Complexes. Synthesis and Structural Characterization

The reaction of Ru5(CO)15(μ5-C) with Ni(COD)2 in acetonitrile at 80 °C affords the bimetallic octahedral ruthenium-nickel cluster complex Ru5Ni(NCMe)(CO)15(μ6-C), 3. The acetonitrile ligand in 3 can be replaced by CO and NH3 to yield Ru5Ni(CO)16(μ6-C), 4, and Ru5Ni(NH3)(CO)15(μ6-C), 5, respectively. Photolysis of compound 3 in benzene and toluene solvent yielded the η(6)-coordinated benzene and toluene Ru5Ni carbido cluster complexes Ru5Ni(CO)13(η(6)-C6H6)(μ6-C), 6, and Ru5Ni(CO)13(η(6)-C7H8)(μ6-C), 7, respectively. All five new compounds were structurally characterized by single-crystal X-ray diffraction analyses.

Near-infrared room temperature emission from a novel class of Ru(ii) heteroleptic complexes with quinonoid organometallic linker

A novel class of luminescent octahedral ruthenium complexes 2-4 displaying a π-bonded quinonoid ligand is described. Remarkably, the presence of this organometallic ligand affects their UV-vis properties and transforms them into panchromatic absorbers. Furthermore, it turns on room temperature NIR emissions.

Symmetry Aspects of H2 Splitting by Five-Coordinate d6 Ruthenium Amides, and Calculations on Acetophenone Hydrogenation, Ruthenium Alkoxide Formation, and Subsequent Hydrogenolysis in a Model trans-Ru(H)2(diamine)(diphosphine) System

The potential energy surface (PES) of H(2) addition to the Ru═N bond of a model five-coordinate ruthenium amide (Ru═N), leading to an octahedral trans-Ru(H)(2)(diamine)(diphosphine) (HRu-NH) and subsequent acetophenone hydrogenation, is studied using M06 density functional theory methods. A qualitative molecular orbital analysis reveals that H(2) addition to the ground state of Ru═N (which has a distorted trigonal-bipyramidal geometry) fits the criterion of a symmetry-forbidden reaction. A transition state (TS) for H(2) heterolytic splitting by Ru═N corresponds to the reaction taking place on an excited state of the Ru═N having a square-pyramidal geometry and gives ΔG°(⧧) = 19.5 kcal/mol. The reaction between HRu-NH and acetophenone proceeds by a localized hydride-transfer TS with ΔG°(⧧) = 11.5 kcal/mol. This TS leads to an ion pair between a square-pyramidal d(6) ruthenium amino cation and the alkoxide and is uphill from the separated reactants by 3.5 kcal/mol. Subsequent abstraction of the amino proton by the alkoxide within the ion pair is barrierless, but it also lacks any thermodynamic driving force. In contrast, reorientation of the alkoxide within the ion pair to form an octahedral ruthenium alkoxide is calculated to be exoergic by 7.1 kcal/mol. These features of the PES suggest that the known rapid production of ruthenium alkoxides when stoichiometric amounts of acetophenone and HRu-NH are reacted at low temperatures proceeds by a simple direct route following hydride transfer. For the simplified model complex, ruthenium alkoxide is calculated to be the thermodynamic product of the hydrogenation reaction (exoergic by 3.6 kcal/mol). A TS for H(2) heterolytic splitting across the Ru-alkoxide bond is calculated to have ΔG°(⧧) (16.0 kcal/mol), slightly smaller than that of H(2) addition to the five-coordinate Ru═N.

Synthesis, structural characterization, electrochemistry and catalytic transfer hydrogenation of ruthenium(II) carbonyl complexes containing tridentate benzoylhydrazone ligands

Convenient synthesis of eight new octahedral ruthenium(II) carbonyl benzoylhydrazone complexes having the general molecular formula [Ru(L)(CO)(EPh3)2] (where E = P or As; H2L = benzoylhydrazone ligand, the two H's representing the two dissociable protons) has been described. The substituted benzoylhydrazone ligands behave as a dianionic tridentate O, N and O donors (L) and coordinates to ruthenium via the phenolate oxygen, the azomethine nitrogen and the deprotonated amide oxygen. The compositions of the complexes have been established by elemental analysis and spectral methods (FT-IR, 1H NMR, 13C NMR, UV–vis). The crystal structure of one of the complexes, [Ru(L2)(CO)(PPh3)2] (2), has been solved by single crystal X-ray crystallography and it indicates the presence of a distorted octahedral geometry in these complexes. All the complexes exhibit metal-to-ligand charge transfer (MLCT) transitions in the visible region and display one quasi-reversible reduction and two irreversible oxidations. Further, the catalytic efficiency of the complexes has been investigated in the case of transfer hydrogenation of ketones to the corresponding secondary alcohols. The influence of base, reaction temperature and catalyst loading in transfer hydrogenation reaction was also evaluated. The complexes were found to be efficient catalysts with conversion up to 99.5% in presence of iso-propanol/KOH.

Synthesis, spectroscopic characterization and in vitro antitumor activities of some novel mononuclear Ru(II) complexes

Abstract The synthesis and spectroscopic characterization of ruthenium complexes ( R-1 to R-8 ) of the type [Ru(A) 2 (B)], (where A = 1,10-phenanthroline/2,2′-bipyridine and B = 3,4,5-tri-OCH 3 -DPC, 4-CH 3 -DPC, 4-N-(CH 3 ) 2 -DPC, 4-NO 2 -DPC are described. These ligands form bidentate octahedral ruthenium complexes. The title complexes were subjected to in vitro cytotoxic activity measurements against the human cancer T-lymphocyte cell lines MTT assay. In vitro evaluation of these ruthenium complexes revealed cytotoxic activity from 0.24 to 1.4 μg/mL against CEM, 0.44 to 1.9 μg/mL against Molt4/C8, 0.28 to 1.5 μg/mL against L1210, 0.24 to 0.98 μg/mL against HL60, and 0.25 to 1.2 μg/mL against BEL7402, depending the nature of the compound.

Bioactive cyclometalated phthalimides: design, synthesis and kinase inhibition.

The regioselective cyclometalation of 4-(pyridin-2-yl)phthalimide was exploited for the economical design of organometallic protein kinase inhibitors. 4-(Pyridin-2-yl)phthalimide can be prepared from inexpensive 4-bromophthalimide in just three steps including one Pd-catalyzed Stille cross-coupling. The versatility of this new ligand was demonstrated with the synthesis of ruthenium(II) half-sandwich as well as octahedral ruthenium(II) and iridium(III) complexes. The regioselectivity of the C-H activation in the course of the cyclometalation can be influenced by the reaction conditions and the steric demand of the introduced metal complex fragment. The biological activity of this new class of metalated phthalimides was evaluated by profiling two representative members against a large panel of human protein kinases. A cocrystal structure of one metallo-phthalimide with the protein kinase Pim1 confirmed an ATP-competitive binding with the intended hydrogen bonding between the phthalimide moiety and the hinge region of the ATP-binding site.

Ruthenium(ii) carbonyl complexes containing benzhydrazone ligands: synthesis, structure and facile one-pot conversion of aldehydes to amides

Convenient synthesis of a series of eight octahedral ruthenium(II) carbonyl complexes having the general molecular formula [Ru(L)(CO)Cl(AsPh3)2] (where HL = thiophene aldehyde benzhydrazone ligand) has been described. The substituted benzhydrazone ligands behave as monoanionic bidentate N and O donors (L) and coordinate to the ruthenium(II) ion via the azomethine nitrogen and deprotonated amide oxygen. The compositions of the complexes have been established by elemental analysis, spectral methods (FT-IR, UV-Vis, 1H NMR) and X-ray crystallography. The crystal structure of two of the complexes, viz., [Ru(L1)(CO)Cl(AsPh3)2] (1) and [Ru(L5)(CO)Cl(AsPh3)2] (5) have been solved by single crystal X-ray crystallography and it indicates the presence of a distorted octahedral geometry in these complexes. The complexes were demonstrated as efficient catalysts for the one-pot conversion of various aldehydes to their corresponding primary amides using NH2OH·HCl and NaHCO3. The effects of solvent, base, reaction temperature and catalyst loading on the catalytic activity of the most active ruthenium(II) carbonyl benzhydrazone complex were also investigated.

Effects of BaRuO3 addition on hydrogen desorption in MgH2

Hydrogen storage in MgH2 is strongly limited by kinetic constraints, so that several additives have been considered in order to improve the rate of hydrogen desorption. The present work is devoted to investigate the effect of BaRuO3 addition on hydrogen absorption and desorption properties of MgH2. BaRuO3 was prepared by solid-state synthesis of BaO and Ru in oxidizing environment. The interaction of as-prepared BaRuO3 with hydrogen at room temperature was examined by thermal desorption and X-ray diffraction experiments, showing that BaRuO3 has the ability to uptake hydrogen in the bulk. The hydrogen interaction is discussed with respect to octahedral ruthenium local environment present in the oxide structure.Addition of 1mol.% BaRuO3 to MgH2 was performed by ball milling. Hydrogen desorption properties were investigated by Sievert and DSC, connected with a H2 detector. The H2 desorbed from of the nano-structured materials is lower than the theoretical content in MgH2, due to the presence of a non-reactive MgO layer. A remarkable increase of the H2 desorption kinetics in nano-structured MgH2 was observed with respect to bare MgH2. The activation energy for hydrogen desorption from MgH2/BaRuO3 mixture was estimated by Arrhenius and Kissinger methods and a value around 130kJmol−1 and 90kJmol−1 was obtained, respectively.

Cell Cycle Arrest, Cytotoxicity, Apoptosis, DNA‐Binding, Photocleavage, and Antioxidant Activity of Octahedral Ruthenium(II) Complexes

AbstractThree ruthenium(II) complexes [Ru(dmp)2(dcdppz)]2+ 1, [Ru(phen)2(dcdppz)]2+ 2, and [Ru(dip)2(dcdppz)]2+ 3 were synthesized and characterized. The crystal structure of complex 1 was solved by single‐crystal X‐ray diffraction. This complex crystallizes in the monoclinic system, space group C2/c with a = 18.454(3) Å, b = 44.648(7) Å, c = 13.082(2) Å, β = 99.911(3)°, R = 0.0571, and Rω = 0.1501. The DNA‐binding constants were determined to be 1.78 (±0.24) × 105, 2.73 (±0.16) × 105, and 7.55 (±0.16) × 105 M–1 for 1, 2, and 3, respectively. The photocleavage of pBR322 DNA by RuII complexes was studied. The retardation assay of pGL 3 plasmid DNA was investigated. The cytotoxicity of complexes 1, 2, and 3 against BEL‐7402, Hela, HepG‐2, and MG‐63 cells was evaluated by the MTT method. Complexes 1 and 3 show higher cytotoxicity than Cisplatin on Hela cells. The apoptosis and cell cycle arrest were investigated, and the antioxidant activities of these complexes were also explored.

Can geometry control the coordination behaviour of 2-hydroxy-1-naphthaldehyde-N(4)-phenylthiosemicarbazone? A study towards its origin

2-Hydroxy-1-naphthaldehyde-N(4)-phenylthiosemicarbazone [H2-Nap-ptsc] (H2L) was reacted with square planar complexes of the type [MCl2(EPh3)2] (where M=Ni or Pd; E=P or As) and octahedral [RuHCl(CO)(PPh3)3]. Square planar complexes ([Ni(Nap-ptsc)PPh3)]; [Pd(Nap-ptsc)PPh3)]; [Pd(Nap-ptsc)AsPh3)]) gave products with only ONS tri coordinated thiosemicarbazone whereas octahedral ruthenium complex gave two products, one with NS and the other with ONS coordination. It is interesting to note that NS bi coordination leads to the formation of more strained four member ring. All the new complexes have been characterised by analytical, spectral, crystallographic and electrochemical methods.

Coordination Driven Self-Assembly and Anticancer Activity of Molecular Rectangles Containing Octahedral Ruthenium Metal Centers.

The synthesis of new 2+2 metalla-rectangles via coordination driven self-assembly of octahedral Ru(II) based acceptors and amide donors is described. To evaluate their in vitro cytotoxic properties, preliminary biological assays were carried out for various human cancer cell lines, and our results show that the cytotoxicity level of 3 is comparable or even greater in the cases of SK-hep-1 and HCT-15 than that of the reference drug cisplatin.