Trans ruthenium(II) complexes with NH-bridged tetradentate symmetric and asymmetric polypyridyl ligands

NH-Bridged tetradentate ligands were synthesized to achieve stable trans Ru(II) bis(polypyridyl) complexes. The polypyridyl part of the ligand was either symmetric, as in N,N-bis(1,10-phenanthroline-2-yl)amine (phen-NH-phen), or asymmetric, as in N-(1,10-phenanthroline-2-yl)-N-(6-yl-dipyridyl[2,3-a:2',3'-c]phenazine)amine (dppz-NH-phen). Protonation of phen-NH-phen with trifluoroacetic acid and the subsequent reaction with RuCl3 yield trans-[Ru(phen-NH-phen)Cl2]. The chloro ligands in this compound can easily be replaced by stronger ligands, such as CH3CN and DMSO. In this way, complexes trans-[Ru(phen-NH-phen)(CH3CN)(DMSO)](PF6)2 (1), trans-[Ru(phen-NH-phen)(DMSO)2](PF6)2 (2), and trans-[Ru(phen-NH-phen)(CH3CN)2](PF6)2 (3) were obtained. X-ray structures were determined for 1 and 3. Following a procedure similar to that used with phen-NH-phen, the complex trans-[Ru(dppz-NH-phen)(CH3CN)2](PF6)2 (4) was obtained. To our knowledge, this is the first reported trans ruthenium(II) bis(polypyridyl) complex with two different polypyridyl ligands in the equatorial plane.     

Novel dinuclear uranyl complexes with asymmetric schiff base ligands: synthesis, structural characterization, reactivity, and extraction studies

The reaction of uranyl nitrate with asymmetric [3O, N] Schiff base ligands in the presence of base yields dinuclear uranyl complexes, [UO2(HL1)]2.DMF (1), [UO2(HL2)]2.2DMF.H2O (2), and [UO2(HL3)]2.2DMF (3) with 3-(2-hydroxybenzylideneamino)propane-1,2-diol (H3L1), 4-((2,3-dihydroxypropylimino)methyl)benzene-1,3-diol (H3L2), and 3-(3,5-di-tert-butyl-2-hydroxybenzylideneamino)propane-1,2-diol (H3L3), respectively. All complexes exhibit a symmetric U2O2 core featuring a distorted pentagonal bipyramidal geometry around each uranyl center. The hydroxyl groups on the ligands are attached to the uranyl ion in chelating, bridging, and coordinate covalent bonds. Distortion in the backbone is more pronounced in 1, where the phenyl groups are on the same side of the planar U2O2 core. The phenyl groups are present on the opposite side of U2O2 core in 2 and 3 due to electronic and steric effects. A similar hydrogen-bonding pattern is observed in the solid-state structures of 1 and 3 with terminal hydroxyl groups and DMF molecules, resulting in discrete molecules. Free aryl hydroxyl groups and water molecules in 2 give rise to a two-dimensional network with water molecules in the channels of an extended corrugated sheet structure. Compound 1 in the presence of excess Ag(NO3) yields {[(UO2)(NO3)(C6H4OCOO)](NH(CH2CH3)3)}2 (4), where the geometry around the uranyl center is hexagonal bipyrimidal. Two-phase extraction studies of uranium from aqueous media employing H3L3 indicate 99% reduction of uranyl ion at higher pH.     

One-pot synthesis of new symmetric and asymmetric xanthene dyes

Symmetric and asymmetric xanthene dyes have been prepared by a convenient one-step procedure from aldehyde and diol or m-aminophenol precursors using concentrated phosphoric acid as a solvent. This protocol provides access to water-soluble dyes with large Stoke’s shifts and far-red fluorescence emission. These compounds are envisioned as components of fluorescence-based sensors for a variety of imaging applications.     

Effects of substituent on the DNA-binding of ruthenium(II) complexes containing asymmetric tridentate intercalative ligands

Three novel unsymmetric tridentate ligands, namely, ptmi (ptmi = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]-5-methoxyisatin), pti (pti = 3-(1,10-phenanthroline-2-yl)-as-triazino-[5,6-f]isatin), ptni (ptni = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]-5-nitroisatin), and their complexes [Ru(tpy)(ptmi)](ClO₄)₂ (tpy = 2,2′:6′,2″-terpyridine) (1), [Ru(tpy)(pti)](ClO₄)₂ (2), and [Ru(tpy)(ptni)](ClO₄)₂ (3) were prepared and characterized by elemental analysis, ¹H NMR, ES–MS. The electrochemical behaviors were studied by cyclic voltammetry. The DNA-binding properties of these complexes were investigated by the spectroscopic method, viscosity measurements, and thermal denaturation. Theoretical studies on these complexes were also performed with the density functional theory (DFT) method. The experimental results showed that these complexes bind to calf thymus (CT-DNA) in an intercalative mode. The order of DNA-binding affinities (A) of these complexes is A(1) < A(2) < A(3). The trend in the DNA-binding affinities of this series of complexes can be reasonably explained by the DFT calculations.     

The reactivity of nitrosyl ruthenium complexes containing polypyridyl ligands

A series of cis nitrosyl complexes containing polypyridyl ligands were prepared and characterized as cis-[RuL(bpy)₂(NO)](PF₆)₃ (L = pyridine, 4-picoline, or 4-acetylpyridine), by elemental analysis, u.v.–vis. and i.r. spectroscopy, and by electrochemical techniques such as cyclic voltammetry, differential pulse voltammetry, spectroelectrochemistry, and coulometry. The complexes exhibit stretching frequencies (NO) at ca. 1950 cm^–1 indicating that nitrosyl group has a sufficiently high degree of nitrosonium ion (NO⁺) character. In non-aqueous solution, the reduction of these complexes induce nitrosyl to nitro conversion. In aqueous solution the reduction product is cis-[RuL(bpy)₂(NH₃)]²⁺ formed by a six electron mechanism. The nitrosyl compounds are susceptible to nucleophilic attack by hydroxide ion. The equilibrium constants were determined.     

Immobilized ruthenium complexes and aspects of their reactivity

Methodologies for the immobilization and characterization of ruthenium complexes into/onto functionalized silica gel, zeolites, polymers, dendrimers, sol–gel, nano and microparticles are described. The corresponding spectroscopic, electrochemical, and photochemical properties as well as chemical reactivities are used for their characterization and study. Comparison between the reactivities of immobilized and in solution species is presented. Some biological applications are also described.     

One-pot synthesis of 2,5-diethynyl-3,4-dibutylthiophene substituted multitopic bipyridine ligands: redox and photophysical properties of their ruthenium(II) complexes

A facile and original synthesis of four 2,2'-bipyridine (bipy) ligands grafted with thiophene subunits is described using phase transfer experimental conditions: related Ru(II) complexes exhibit well-defined redox and photophysical properties which were probed by cyclic voltammetry, UV-vis, steady-state emission and transient absorption spectroscopy.     

Synthesis and reactivity of ruthenium complexes with 1,1′-dithiolate ligands

Reactions of [Ru(PPh₃)₃Cl₂] with ROCS₂K in THF at room temperature and at reflux gave the kinetic products trans-[Ru(PPh₃)₂(S₂COR)₂] (R = ⁿPr 1, ⁱPr 2) and the thermodynamic products cis-[Ru(PPh₃)₂(S₂COR)₂] (R = ⁿPr 3, ⁱPr 4), respectively. Treatment of [RuHCl(CO)(PPh₃)₃] with ROCS₂K in THF afforded [RuH(CO)-(S₂COR)(PPh₃)₂] (R = ⁿPr 5, ⁱPr 6) as the sole isolable products. Reaction of [RuCl₂(PPh₃)₃] with tetramethylthiuram disulfide [Me₂NCS₂]₂ gave a Ru(III) dithiocarbamate complex, [Ru(PPh₃)₂(S₂CNMe₂)Cl₂] (7). This reaction involved oxidation of ruthenium(II) to ruthenium(III) by the disulfide group in [Me₂NCS₂]₂. Treatment of 7 with 1 equiv. of [M(MeCN)₄][ClO₄] (M = Cu, Ag) gave the stable cationic ruthenium(III)-alkyl complexes [Ru{C(NMe₂)QC(NMe₂)S}(S₂CNMe₂)(PPh₃)₂][ClO₄] (Q = O 8, S 9) with ruthenium-carbon bonds. The crystal structures of complexes 1, 2, 4·CH₂Cl₂, 6, 7·2CH₂Cl₂, 8, and 9·2CH₂Cl₂ have been determined by single-crystal X-ray diffraction. The ruthenium atom in each of the above complexes adopts a pseudo-octahedral geometry in an electron-rich sulfur coordination environment. The 1,1′-dithiolate ligands bind to ruthenium with bite S-Ru-S angles in the range of 70.14(4)-71.62(4)°. In 4·CH₂Cl₂, the P-Ru-P angle for the mutually cis PPh₃ ligands is 103.13(3)°, the P-Ru-P angles for other complexes with mutually trans PPh₃ ligands are in the range of 169.41(4)-180.00(6)°. The alkylcarbamate [C(NMe₂)QC(NMe₂)S]⁻ (Q = O, S) ligands in 8 and 9 are planar and bind to the ruthenium centers via the sulfur and carbon atoms from the CS and NC double bonds, respectively. The Ru-C bond lengths are 1.975(5) and 2.018(3) Å for 8 and 9·2CH₂Cl₂, respectively, which are typical for ruthenium(III)-alkyl complexes. Spectroscopic properties along with electrochemistry of all complexes are also reported in the paper.     

Novel C-H activation and C-S formation reactions on disulfide and diselenide ligands in dinuclear ruthenium complexes

The C-S bond formation reactions of the transition metal sulfides with organic molecules are collected and reviewed to understand the reactivity of the sulfide ligands supported by the transition metals. As an example of the role of the sulfide, the C-H bond activation is focused and discussed.     

Unsymmetrical tren-based ligands: synthesis and reactivity of rhenium complexes

Reaction of bis(2-aminoethyl)(3-aminopropyl)amine with C(6)F(6) and K(2)CO(3) in DMSO yields unsymmetrical [(C(6)F(5))HNCH(2)CH(2)](2)NCH(2)CH(2)CH(2)NH(C(6)F(5)) ([N(3)N]H(3)). The tetraamine acts as a tridentate ligand in complexes of the type H[N(3)N]Re(O)X (X = Cl 1, Br 2) prepared by reacting Re(O)X(3)(PPh(3))(2) with [N(3)N]H(3) and an excess of NEt(3) in THF. Addition of 1 equiv of TaCH(CMe(2)Ph)Br(3)(THF)(2) to 1 gives the dimeric compound H[N(3)N]ClReOReBrCl[N(3)N]H (3) in quantitative yield that contains a Re(V)[double bond]O[bond]Re(IV) core with uncoordinated aminopropyl groups in each ligand. Addition of 2 equiv of TaCH(CMe(2)Ph)Cl(3)(THF)(2) to 1 leads to the chloro complex [N(3)N]ReCl (4) with all three amido groups coordinated to the metal, whereas by addition of 2 equiv of TaCH(CMe(2)Ph)Br(3)(THF)(2) to 2 the dibromo species H[N(3)N]ReBr(2) (5) with one uncoordinated amino group is isolated. Reduction of 4 under an atmosphere of dinitrogen with sodium amalgam gives the dinitrogen complex [N(3)N]Re(N(2)) (6). Single-crystal X-ray structure determinations have been carried out on complexes 1, 3, 5, and 6.     

The synthesis and reactivity of some indenyl and bis-indenyl ruthenium carbonyl complexes

The reaction of [Ru₃(CO)₁₂] (1), with indene in refluxing xylene affords [{(η⁵-C₉H₇)Ru(CO)₂}₂] (2), in high yield. An analogous reaction of 1 with 2-phenylindene affords the expected dinuclear complex [{(η⁵-C₉H₆Ph)Ru(CO)₂}₂] (5), and a heptaruthenium cluster [(C₉H₄Ph)Ru₇(μ-H)(μ-CO)₂(CO)₁₆] (6). The indenyl ligand in compound 6 exhibits a novel bonding mode in which the benzenoid ring is μ₄,η¹:η¹:η²:η² bound to the cluster. Refluxing 1 with bis-indenyl methane affords the dinuclear complex [Ru₂(CO)₄{μ-(η⁵-C₉H₆)₂CH₂}] (7), which reacts with iodine via Ru-Ru bond cleavage to give [Ru₂I₂(CO)₄{(η⁵-C₉H₆)₂CH₂}] (8).     

Crystallization-induced asymmetric transformation of chiral-at-metal ruthenium(II) complexes bearing achiral ligands

Recently, we observed that the enantiopure Lambda form of the tributylammonium salt of the chiral anion tris[tetrachlorobenzene-1,2-bis(olato)]phosphate, also named Trisphat, was able to induce an efficient resolution of a Delta,Lambda racemic mixture of cis-[Ru(dmp)2(NCCH3)2](PF6)2 (dmp=2,9-dimethyl-1,10-phenanthroline) due to the spontaneous and selective precipitation of the heterochiral pair [Delta-Ru(dmp)2(CH3CN)2][Lambda-Trisphat]2. We report here that the combination of such a stereoselective precipitation process and irradiation results in the quantitative conversion of the initial [Ru(dmp)2(NCCH3)2]2+ racemate into only one of the two enantiomers. This is the first example in inorganic chemistry of an asymmetric transformation that leads to a chiral complex with no chiral ligand. Finally, three new racemic ruthenium bis(diimine) complexes, namely [Ru(dmp)2(NCCH3)Py](PF6)2 (Py=pyridine), [Ru(dmp)2(1,3-diaminopropane)](PF6)2, and [Ru(dmp)2(ethylenediamine)](PF6)2 were synthesized. For all of them, crystallization-induced asymmetric transformation proved to be an efficient way of obtaining the corresponding optically active chiral-at-metal complexes in high yields and with excellent stereoselectivities.     

Applications of ruthenium hydride borohydride complexes containing phosphinite and diamine ligands to asymmetric catalytic reactions

[reaction: see text] A series of novel trans-ruthenium hydride borohydride complexes with chiral phosphinite and diamine ligands were synthesized. They can be used in the asymmetric transfer hydrogenation of aryl ketones, including base-sensitive ones, to give chiral alcohols in moderate to good enantioselectivities (up to 94% ee). They are also efficient catalysts for the Michael addition of malonates to enones with enantioselectivities of up to 90%. This kind of catalyst allows a one-pot tandem Michael addition/H(2) hydrogenation protocol to build structures with multiple chiral centers.     

Metal-metal interactions in dinuclear ruthenium complexes containing bridging 4,5-di(2-pyridyl)imidazolates and related ligands

The dinuclear bis(2,2'-bipyridine)ruthenium complex of 4,5-di(2-pyridyl)imidazolate has been prepared and separated into its (meso and rac) diastereoisomers. The 2-phenyl substituted analogue forms the meso isomer selectively. All three complexes have been characterised by 1H NMR and X-ray crystallography. Electrochemical measurements and spectroelectrochemistry of the mixed-valence states reveal strong metal-metal interactions and IVCT bands that are highly dependent on the electrolyte.     

Effects of phosphine ligand chelation on the reactivity of monomeric parent amido ruthenium complexes: synthesis and reactivity of such a complex bearing monodentate ligands

The parent amido complex cis-(PMe(3))(4)Ru(H)(NH(2)) (2) has been prepared via the deprotonation of [cis-(PMe(3))(4)Ru(H)(NH(3))(+)][BPh(4)(-)]. The amido complex is a somewhat weaker base than the DMPE analogue trans-(DMPE)(2)Ru(H)(NH(2)) but is still basic enough to quantitatively deprotonate fluorene and reversibly deprotonate 1,3-cyclohexadiene and toluene. Complex 2 exhibits very labile phosphine ligands, two of which can be replaced by DMPE to yield the mixed complex cis-(PMe(3))(2)(DMPE)Ru(H)(NH(2)). Because of the ligand lability, 2 also undergoes hydrogenolysis and rapid exchange with labeled NH(3). The amide complex reacts with alkyl halides to yield E2 and S(N)2 products, along with ruthenium hydrido halide complexes including the ruthenium fluoride cis-(PMe(3))(4)Ru(H)(F). Ruthenium hydrido ammonia halide ion pair intermediates [cis-(PMe(3))(4)Ru(H)(NH(3))(+)][X(-)] are observed in some deprotonation and E2 reactions, and measurement of the equilibrium constants for NH(3) displacement from these complexes suggests that they benefit from significant hydrogen bonding between X(-) and NH(3) groups. Cumulenes also react with complex 2 to afford the products of insertion into an NH bond. The rates of neither these NH insertion reactions nor the reversible deprotonation reactions show any dependence on the concentration of PMe(3) present, suggesting that these reactions take place directly at the NH(2) group and do not involve precoordination of substrate to the metal center.     

Mono- and dinuclear ruthenium carbonyl complexes with redox-active dioxolene ligands: electrochemical and spectroscopic studies and the properties of the mixed-valence complexes

The mononuclear complex [Ru(PPh(3))(2)(CO)(2)(L(1))] (1; H(2)L(1) = 7,8-dihydroxy-6-methoxycoumarin) and the dinuclear complexes [[Ru(PPh(3))(2)(CO)(2)](2)(L(2))][PF(6)] [[2][PF(6)]; H(3)L(2) = 9-phenyl-2,3,7-trihydroxy-6-fluorone] and [[Ru(PBu(3))(2)(CO)(2)](2)(L(3))] (3; H(4)L(3) = 1,2,3,5,6,7-hexahydroxyanthracene-9,10-dione) have been prepared; all complexes contain one or two trans,cis-[Ru(PR(3))(2)(CO)(2)] units, each connected to a chelating dioxolene-type ligand. In all cases the dioxolene ligands exhibit reversible redox activity, and accordingly the complexes were studied by electrochemistry and UV/vis/NIR, IR, and EPR spectroscopy in their accessible oxidation states. Oxidation of 1 to [1](+) generates a ligand-centered semiquinone radical with some metal character as shown by the IR and EPR spectra. Dinuclear complexes [2](+) and 3 show two reversible ligand-centered couples (one associated with each dioxolene terminus) which are separated by 690 and 440 mV, respectively. This indicates that the mixed-valence species [2](2+) has greater degree of electronic delocalization between the ligand termini than does [3](+), an observation which was supported by IR, EPR, and UV/vis/NIR spectroelectrochemistry. Both [2](2+) and [3](+) have a solution EPR spectrum consistent with full delocalization of the unpaired electron between the ligand termini on the EPR time scale (a quintet arising from equal coupling to all four (31)P nuclei); [3](+) is localized on the faster IR time scale (four CO vibrations rather than two, indicative of inequivalent [Ru(CO)(2)] units) whereas [2](2+) is fully delocalized (two CO vibrations). UV/vis/NIR spectroelectrochemistry revealed the presence of a narrow, low-energy (2695 nm) transition for [3](+) associated with the catecholate --> semiquinone intervalence transition. The narrowness and solvent-independence of this transition (characteristic of class III mixed-valence character) coupled with evidence for inequivalent [Ru(CO)(2)] termini in the mixed-valence state (characteristic of class II character) place this complex at the class II-III borderline, in contrast to [2](2+) which is clearly class III.     

Redox-associated eta(1) to eta(2) conversion of disulfide ligands in dinuclear ruthenium complexes

Disulfide-bridged dinuclear ruthenium complexes [[Ru(MeCN)(P(OMe)(3))(2)](2)(mu-X)(mu,eta(2)-S(2))][ZnX(3)(MeCN)] (X = Cl (2), Br (4)), [[Ru(MeCN)(P(OMe)(3))(2)](2)(mu-Cl)(2)(mu,eta(1)-S(2))](CF(3)SO(3)) (5), [[Ru(MeCN)(P(OMe)(3))(2)](2)(mu-Cl)(mu,eta(2)-S(2))](BF(4)) (6), and [[Ru(MeCN)(2)(P(OMe)(3))(2)](2)(mu-Cl)(mu,eta(1)-S(2))](CF(3)SO(3))(3) (7) were synthesized, and the crystal structures of 2 and 4 were determined. Crystal data: 2, triclinic, P1, a = 15.921(4) A, b = 17.484(4) A, c = 8.774(2) A, alpha = 103.14(2) degrees, beta = 102.30(2) degrees, gamma = 109.68(2) degrees, V = 2124(1) A(3), Z = 2, R (R(w)) = 0.055 (0.074); 4, triclinic, P1 a = 15.943(4) A, b = 17.703(4) A, c = 8.883(1) A, alpha = 102.96(2) degrees, beta = 102.02(2) degrees, gamma = 109.10(2) degrees, V = 2198.4(9) A(3), Z = 2, R (R(w)) = 0.048 (0.067). Complexes 2 and 4 were obtained by reduction of the disulfide-bridged ruthenium complexes [[RuX(P(OMe)(3))(2)](2)(mu-X)(2)(mu,eta(1)-S(2))] (X = Cl (1), Br (3)) with zinc, respectively. Complex 5 was synthesized by oxidation of 2 with AgCF(3)SO(3). Through these redox steps, the coordination mode of the disulfide ligand was converted from mu,eta(1) in 1 and 3 to mu,eta(2) in 2 and 4 and further reverted to mu,eta(1) in 5. Electrochemical studies of 6 indicated that similar conversion of the coordination mode occurs also in electrochemical redox reactions.     

Preparation and reactivity of p-cymene complexes of ruthenium and osmium incorporating 1,3-triazenide ligands

p-Cymene complexes MCl₂(η⁶-p-cymene)L [M = Ru, Os; L = P(OEt)₃, PPh(OEt)₂, (CH₃)₃CNC] were prepared by allowing [MCl(μ-Cl)(η⁶-p-cymene)]₂ to react with phosphites or tert-butyl isocyanide. Treatment of MCl₂(η⁶-p-cymene)L complexes with 1,3-ArNNN(H)Ar triazene and an excess of NEt₃ gave the cationic triazenide derivatives [M(η²-1,3-ArNNNAr)(η⁶-p-cymene)L]BPh₄ (Ar = Ph, p-tolyl). Neutral triazenide complexes MCl(η²-1,3-ArNNNAr)(η⁶-p-cymene) (M = Ru, Os) were also prepared by allowing [MCl(μ-Cl)(η⁶-p-cymene)]₂ to react with 1,3-diaryltriazene in the presence of triethylamine. p-Cymene complexes MCl₂(η⁶-p-cymene)L reacted with equimolar amounts of 1,3-ArNNN(H)Ar triazene to give both triazenide complexes [M(η²-1,3-ArNNNAr)(η⁶-p-cymene)L]BPh₄ and amine derivatives [MCl(ArNH₂)(η⁶-p-cymene)L]BPh₄. A reaction path for the formation of the amine complex is also reported. The complexes were characterised by spectroscopy and X-ray crystallography of RuCl₂(η⁶-p-cymene)[PPh(OEt)₂] and [Ru(η²-1,3-p-tolyl-NNN-p-tolyl)(η⁶-p-cymene){CNC(CH₃)₃}]BPh₄. Selected triazenide complexes were studied as catalysts in the hydrogenation of 2-cyclohexen-1-one and cinnamaldehyde.     

Preparation and characterization of asymmetric alpha-alkoxy dipyrrin ligands and their metal complexes

Asymmetric alpha-substituted dipyrrins have been synthesized and characterized. The compounds were formed by a metal mediated reaction involving a single alkoxy group substituted into the alpha-position of an alpha,beta-unsubstituted dipyrrin. An alpha-methoxy dipyrrin, 5-(4-cyanophenyl)-1-methoxydipyrrin (alpha-OMe-4-cydpm), was prepared from 5-(4-cyanophenyl)-4,6-dipyrromethane. Methoxy, ethoxy, and propoxy derivatives (alpha-OMe-4-mecdpm, alpha-OEt-4-mecdpm, alpha-OPr-4-mecdpm) of 5-(4-methoxycarbonylphenyl)-4,6-dipyrromethane have also been prepared. A homoleptic, bis(1-methoxy)dipyrrinato zinc(II) complex, [Zn(alpha-OMe-4-mecdpm)(2)], has been synthesized, as has a heteroleptic cobalt(III) complex with one alpha-OMe-4-cydpm ligand and two unsubstituted 5-(4-cyanophenyl)dipyrrin (4-cydpm) ligands ([Co(alpha-OMe-4-cydpm)(4-cydpm)(2)]). The rotational barrier of the meso-aryl substituent of [Zn(alpha-OMe-4-mecdpm)(2)] was found to be 17.3 kcal mol(-1) by variable-temperature NMR spectroscopy. The compounds alpha-OMe-4-cydpm and [Zn(alpha-OMe-4-mecdpm)(2)] have also been characterized by X-ray diffraction. The formation of the new dipyrrin derivatives is shown to be general and can be performed on dipyrrins with various meso-aryl substitutents, with a variety of alcohols, and can be promoted by several metal salts.     

New ruthenium metathesis catalysts with chelating indenylidene ligands: synthesis, characterization and reactivity

Six new ruthenium complexes bearing a bidentate (κ(2)O,C)-isopropoxy-indenylidene and PPh(3) or PCy(3) ligands have been synthesized and characterized by (1)H, (13)C NMR spectroscopy and X-ray crystallography. Some of these complexes were synthesized in dimethyl carbonate, a green solvent that was recently shown to be suitable for several catalytic transformations including olefin metathesis. The thermal stability and catalytic efficiency of the PCy(3)-containing complexes have been evaluated in a series of test reactions.