Regulation of electron donating ability to metal center: isolation and characterization of ruthenium carbonyl complexes with N,N- and/or N,O-donor polypyridyl ligands

Polypyridyl ruthenium(II) dicarbonyl complexes with an N,O- and/or N,N-donor ligand, [Ru(pic)(CO)₂Cl₂]⁻ (1), [Ru(bpy)(pic)(CO)₂]⁺ (2), [Ru(pic)₂(CO)₂] (3), and [Ru(bpy)₂(CO)₂]²⁺ (4) (pic=2-pyridylcarboxylato, bpy=2,2′-bipyridine) were prepared for comparison of the electron donor ability of these ligands to the ruthenium center. A carbonyl group of [Ru(L1)(L2)(CO)₂]ⁿ (L1, L2=bpy, pic) successively reacted with one and two equivalents of OH⁻ to form [Ru(L1)(L2)(CO)(C(O)OH)]ⁿ⁻¹ and [Ru(L1)(L2)(CO)(CO₂)]ⁿ⁻². These three complexes exist as equilbrium mixtures in aqueous solutions and the equilibrium constants were determined potentiometrically. Electrochemical reduction of 2 in CO₂-saturated CH₃CN–H₂O at −1.5 V selectively produced CO.     

Protonation of Cp(CO)(PPh3) RuCCPh: Formation of cationnic phenylacetylene and phenylvinylidene complexes and subsequent reaction with ethylene oxide to form the net [2 + 3] cycloadduct [Cp(CO)(PPH3)Ru=CCH(Ph)CH2CH2O]+

Protonation of the alkynyl complex Cp(CO)(PPh₃)RuCCPh (1) at low temperature affords quantitatively the vinylidened complex [Cp(CO)(PPh₃)RuCCH(Ph)]⁺ (3), which upon warming to room temperature forms an equilibrium with the η²-phenylacetylene complex [Cp(CO)(PPh₃)Ru(η²-HCCPh)]⁺ (4), with the latter predominating. Subsequent reaction with ethylene oxide yields the cyclic oxacarbene complex [Cp(CO)(PPH₃)Ru=CCH(Ph)CH₂CH₂O]⁺ (5), which can be regarded as the result of a net [3+2] cycloaddition reaction between 3 and ethylene oxide. Depronation of 5 affords teh corresponding neutral cyclic vinyl complex [Cp(CO)(PPH₃)RuC=C(Ph)CH₂CH₂O]⁺ (6), which can in turn be protonated to regenerate 5 in a diastereoselective manner. The structures of complexes 5 and 6 were determined by X-ray crystallography.     

Synthesis and structure of new copper(II) coordination compounds with 8-quinoline aldehyde semicarbazones and thiosemicarbazones

Copper(II) salts were reacted with various quinoline aldehyde chalcogensemicarbazones to yield compounds formulated as Cu(HL)X₂ · nH₂O (I: HL = quinoline aldehyde thiosemicarbazone (HL¹), X = ClO₄, n = 2; II: HL = quinoline aldehyde 4-C₂H₅-thiosemicarbazone (HL^1a), X = NO₃, n = 0; III: HL = quinoline aldehyde semicarbazone (HL²), X = ClO₄, n = 3 and IV: HL = quinoline aldehyde 4-Ph-semicarbazone (HL^2a), X = NO₃, n = 1). Regardless of the reagent ratio, the products were compounds having the metal: ligand ratio of 1: 1, where the organic ligand was coordinated tridentate in a molecular form. Single-crystal X-ray diffraction showed that, depending on the chalcogen atom in the organic ligand (S or O), the substituent in the 4th position (at the terminal nitrogen atom), and the specifics of the acido ligand, complexes I–IV had appreciably differing molecular structure organizations. The structures of I and III are formed by a 1D charged coordination polymer, ClO ₄ ^? anions, and water molecules and may be described by the formula [Cu(HL)(H₂O)(ClO₄)] _n (ClO₄) _n · nH₂O. Copper(II) coordination polyhedra in I and II are (4 + 2) and (4 + 1 + 1) tetragonal bipyramids, respectively. In II and IV, the structures are monomeric and can be described as [Cu(HL^1a)(NO₃)₂] with the metal coordination polyhedron shaped as a (4 + 1) tetragonal pyramid in II and as [Cu(HL^2a)(H₂O)(NO₃)](NO₃) with the metal coordination polyhedron shaped as a (3 + 2) trigonal bipyramid in IV. The structure of II is built of molecular complexes, each comprising, apart from ligand HL^1a, two monodentate coordinated NO ₃ ^? groups. The oxygen atom of one anion together with the NNS donor atom set of ligand HL^1a form the base, and the oxygen atom of the other anion is in the apex of the coordination polyhedron. In IV, the structure is ionic and built of NO ₃ ^? anions and [Cu(HL^2a)(H₂O)(NO₃)]⁺ complex cations, where a cationic coordination polyhedron has a trigonal-bipyramidal configuration with organic ligand HL^2a positioned along the long edge. The bipyramidal base is made up by the oxygen atoms of the coordinated water molecule and monodentate nitrato group and the nitrogen atom N2 of the azomethyne group.     

Structures, preparation and catalytic activity of ruthenium cyclopentadienyl complexes based on pyridyl-phosphine ligand

Ruthenium complexes [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(PPh₃)Cl] (1) and [(η⁵-C₅H₅)Ru(κ²-P-N-PPh₂Py)(PPh₃)]⁺ (1a) containing diphenyl-2-pyridylphosphine (PPh₂Py) are reported. Coordinated PPh₂Py in the complex [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(PPh₃)Cl] (1) exhibits monodentate behavior. In presence of NH₄PF₆ in methanol at room temperature it afforded chelated complex [(η⁵-C₅H₅)Ru(κ²-P,N-PPh₂Py)(PPh₃)]⁺ (1a). Further, 1 reacted with various species viz., CH₃CN, NaCN, NH₄SCN and NaN₃ to afford cationic and neutral complexes [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(PPh₃)L]⁺ and [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(PPh₃)L] [L = CH₃CN (1b); CN⁻ (1c); N₃⁻ (1d) and SCN⁻ (1e)] and it’s reaction with N,N-donor chelating ligands dimethylglyoxime (H₂dmg) and 1,2-phenylenediamine (pda) gave cationic complexes [(η⁵-C₅H₅)Ru(κ¹-P-PPh₂Py)(κ²-N-N)]PF₆ [κ²-N-N = dmg (1f) and pda (1g)]. The complexes 1-1g have been characterized by physicochemical techniques and crystal structures of 1, 1a, 1c, 1e and 1f have been determined by single crystal X-ray analyses. Catalytic potential of the complex 1 has been evaluated in water under aerobic conditions. It was observed that the complex 1 selectively catalyzes reduction of aldehyde into alcohol.     

The reactions of [Fe2(η-C5H5)2(CO)4−n(CNMe)n] (n = 0–4) complexes with halogens and mercury(II) salts

Halogens, X₂, and HgY₂ (X = Cl, Br, I; Y = X, F, NO₃, BF₄) cleave the metalmetal bonds in [Fe₂(η-C₅H₅)₂(CO)_4−n(CNMe)_n] complexes (n = 0–4). Typically, e.g., when n = 2, X₂ electrophiles give [Fe(η-C₅H₅)(CO)(CNMe)X] (a) and [Fe(η-C₅H₅)(CO)(CNMe)₂]X (b) in relative yields which depend on X, the reaction solvent and n, but HgY₂ give equimolar amounts of [Fe(η-C₅H₅)(CNMe)₂Y] (c and [Fe(η-C₅H₅)(CO)₂HgY] only. Hg(CN)₂ reacts more slowly than other HgY₂, and [Hg(PPh₃)₂I₂] does not react at all. It is suggested that the reactions which give rise to products of type (a), (b) or (c) are all two-electron oxidation which proceed by way of adducts containing μ-CA → X₂ or μ-CA → HgX₂ groups (Ca = CO or CNMe). One of these adducts has been isolated, namely [Fe₂(η-C₅H₅)₂(CNMe)₂{μ-CN(Me)HgCl₂}₂] · CHCl₃.     

Gas-phase halo alkylation of C60-fullerene by ion-molecule reaction under chemical ionization

Chemical ionization (CI) mass spectra of C₆₀-fullerene were studied using 1,2-dibromoethane and 1,2-dichloroethane as CI reagents. The ion-molecule reaction between C₆₀ and C₂H₄X⁺ (X=Br and Cl) leads to the formation of (C₆₀+C₂H₄X)⁺ adducts. The collision-induced dissociation of the adducts reveal gas phase halo alkylation of C₆₀-fullerence involving the C?C bond formation.     

Chiral arene ruthenium complexes: Part 3. [Ruthenium(η6-arene)(η4-1,5-cyclooctadiene)] complexes with N or O donor functions in the arene side chain

Arene ruthenium(0) complexes with carbonyl side chain functionalities like [Ru(η⁶-C₆H₅COR)(η⁴-COD)] or [Ru(η⁶-o-C₆H₄{R¹}COR)(η⁴-COD)] (COD=1,5-cyclooctadiene; R=H, CH₃; R¹=H, CH₃, OCH₃) are easily accessible by replacing the naphthalene ligand of [Ru(η⁶-naphthalene)(η⁴-COD)] (1) through an arene exchange reaction. These carbonyl species are susceptible to standard organic reactions of the carbonyl function, thus allowing the introduction of dangling side chains bearing highly polar functions like hydroxyl or amino groups. Aldol reaction of [Ru(o-C₆H₄{CH₃}COCH₃)(COD)] (3) with (−)-menthylchloroformate in the presence of LDA (LDA=lithium diisopropylamide) leads to a diastereomeric mixture of [Ru(menthyl-{3-oxo-3-η⁶-o-tolyl}propionate)(COD)] (10). However, treatment of 3 with LDA and o-tolylaldehyde or benzaldehyde affords the unexpected products [Ru(1-η⁶-o-tolyl-3-o-tolylpropan-1-one)(COD)] (11) and [Ru(1-η⁶-o-tolyl-1-phenylpropan-1-one)(COD)] (12). A diastereoselective addition (88% de) of deprotonated menthylacetate to [Ru(o-tolylaldehyde)(COD)] (4) results in the formation of [Ru(menthyl 3-η⁶-o-tolyl-3-hydroxypropionate)(COD)] (13). Racemic planar-chiral aldehyde complexes 2 and 4 react with amines giving the imination products in good yield. In case of reaction between 2 and (R)-N-amino-2-(methoxymethyl)-pyrrolidine (RAMP), diastereomeric [Ru(N-[[η⁶-(2-methylphenyl]methylene]-(R)-2-(methoxymethyl)-1-pyrrolidinamine)(COD)] (17) is formed. The diastereomers (R,R)-17 and (S,R)-17 have been separated by fractional crystallisation. Asymmetric arene ruthenium complexes with a defined planar-chiral configuration are thus accessible. Reduction of [Ru(3-η⁶-phenyl-(R)-methylbutyrate)(COD)] (7) with LiAlH₄ yields the chiral γ-alcohol [Ru(3-η⁶-phenyl-(R)-1-butanol)(COD)] (18). A Wittig olefination converts the aldehyde complex 4 into a mixture of E- and Z-isomeric [Ru(1-η⁶-o-tolyl-2-phenylethylene)(COD)] 21a and 21b, which were separated again by fractional crystallisation.     

Preparation and reactivity of half-sandwich hydrazine complexes of ruthenium and osmium

Hydrazine complexes [MCl(η⁶-p-cymene)(RNHNH₂)L]BPh₄ (1–6) [M = Ru, Os; R = H, Me, Ph; L = P(OEt)₃, PPh(OEt)₂, PPh₂OEt] were prepared by allowing dichloro complexes MCl₂(η⁶-p-cymene)L to react with hydrazines RNHNH₂ in the presence of NaBPh₄. Treatment of ruthenium complexes [RuCl(η⁶-p-cymene)(RNHNH₂)L]BPh₄ with Pb(OAc)₄ led to acetate complex [Ru(κ²–O₂CCH₃)(η⁶-p-cymene)L]BPh₄ (7). Instead, the reaction of osmium derivatives [OsCl(η⁶-p-cymene)(CH₃NHNH₂)L]BPh₄ with Pb(OAc)₄ afforded the methyldiazenido complex [Os(CH₃N₂)(η⁶-p-cymene)L}]BPh₄ (8). Treatment with HCl of this diazenido complex 8 led to the methyldiazene cation [OsCl(CH₃NNH)(η⁶-p-cymene)L}]⁺ (9⁺). The complexes were characterised spectroscopically and by X-ray crystal structure determination of [OsCl(η⁶-p-cymene)(PhNHNH₂){PPh(OEt)₂}]BPh₄ (6b) and [Ru(κ²–O₂CCH₃)(η⁶-p-cymene){PPh(OEt)₂}]BPh₄ (7b).     

N,N′-Bis(aryl)pyridine-2,6-dicarboxamide complexes of ruthenium: Synthesis,structure and redox properties

Reaction of five N,N′-bis(aryl)pyridine-2,6-dicarboxamides (H₂L-R, where H₂ denotes the two acidic protons and R (R = OCH₃, CH₃, H, Cl and NO₂) the para substituent in the aryl fragment) with [Ru(trpy)Cl₃](trpy = 2,2′,2″-terpyridine) in refluxing ethanol in the presence of a base (NEt₃) affords a group of complexes of the type [Ru^II(trpy)(L-R)], each of which contains an amide ligand coordinated to the metal center as a dianionic tridentate N,N,N-donor along with a terpyridine ligand. Structure of the [Ru^II(trpy)(L-Cl)] complex has been determined by X-ray crystallography. All the Ru(II) complexes are diamagnetic, and show characteristic ¹H NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry on the [Ru^II(trpy)(L-R)] complexes shows a Ru(II)–Ru(III) oxidation within 0.16–0.33 V versus SCE. An oxidation of the coordinated amide ligand is also observed within 0.94–1.33 V versus SCE and a reduction of coordinated terpyridine ligand within −1.10 to −1.15 V versus SCE. Constant potential coulometric oxidation of the [Ru^II(trpy)(L-R)] complexes produces the corresponding [Ru^III(trpy)(L-R)]⁺ complexes, which have been isolated as the perchlorate salts. Structure of the [Ru^III(trpy)(L-CH₃)]ClO₄ complex has been determined by X-ray crystallography. All the Ru(III) complexes are one-electron paramagnetic, and show anisotropic ESR spectra at 77 K and intense LMCT transitions in the visible region. A weak ligand-field band has also been shown by all the [Ru^III(trpy)(L-R)]ClO₄ complexes near 1600 nm.     

Synthesis and reactivity of 2-(tert-butylcyclopentadienyl)-indenyl dinuclear ruthenium complex [η5:η5-(tBuC5H3)(C9H6)]Ru2(CO)4: Halogen induced Ru cleavage from indenyl ring

Thermal reaction of Ru₃(CO)₁₂ with unsymmetrical Fv ligand 2-(tert-butylcyclopentadienyl)-indene provided [η⁵:η⁵-(^tBuC₅H₃)(C₉H₆)]Ru₂(CO)₄ (2) in good yield. When 2 reacted with three or more equivalent of halogen X₂, compounds [(η⁵-^tBuC₅H₃)(C₉H₆X)]Ru(CO)₂X (X = Br, 3; I, 4) were isolated in moderate yield. In complexes 3 and 4 only the Cp rings were coordinated with Ru(CO)₂X, along with uncomplexed halogenated-indenyl rings. All the new complexes have been fully characterized. X-ray characterization of 2, 3, and 4 are also provided.     

Synthesis of single and double butterfly iron carbonyl complexes by reactions of [(μ-RSe)(μ-CO)Fe2(CO)6]− anions. Crystal structures of (μ-p-MeC6H4Se)[μ-PhCH2N(H)CS]Fe2(CO)6 and [(μ-PhSe)(μ-MeAs)Fe2(CO)6]2

The in situ reactions of the [Et₃NH]⁺ and [MgBr]⁺ salts of [(μ-RSe)(μ-CO)Fe₂(CO)₆]⁻ (1) anions with PhC(Cl)NPh gave single butterfly complexes (μ-RSe)(μ-PhCNPh)Fe₂(CO)₆ (2, R=Ph; 3, R=p-MeC₆H₄; 4, R=Et), whereas those of the [Et₃NH]⁺ salts of 1 with R′NCS afforded single butterfly complexes (μ-RSe)[μ-R′N(H)CS]Fe₂(CO)₆ (5, R=Ph, R′=Ph; 6, R=p-MeC₆H₄ R′=Ph; 7, R=p-MeC₆H₄, R′=PhCO; 8, R=p-MeC₆H₄, R′=PhCH₂). Compound 8 could also be prepared by reaction of the [MgBr]⁺ salt of 1 (R=p-MeC₆H₄) with PhCH₂NCS followed by treatment with CF₃CO₂H. More interestingly, while the [Et₃NH]⁺ salt of 1 (R=Ph) reacted with Et₃OBF₄ to give a carbyne ligand-bridged single butterfly complex (μ-PhSe)(μ-EtOC)Fe₂(CO)₆ (9), reaction of the [Et₃NH]⁺ salt of 1 (R=Ph) with MeAsI₂ produced a MeAsAsMe ligand-bridged double butterfly complex [(μ-PhSe)(μ-MeAs)Fe₂(CO)₆]₂ (10). All the new complexes, 2–10, were characterized by elemental analysis and various spectroscopic methods, for complexes 8 and 10, the structures were also confirmed by X-ray diffraction techniques.     

Adducts of coordination compounds-XIII. Nitrates,hydrogen and silver dinitrates,and polysilver nitrates of trans-dihalotetrakispyridinerhodium(III) and iridium(III) ions

The synthesis and characterization, chiefly as salts of the anions [X(ONO₂)₂]⁻ (X = H⁺ or Ag⁺) (by analysis, X-ray powder photography, vibrational spectra and thermogravimetry) of adducts of the nitrates trans-[M(L)₄X₂](NO₃) (M =Rh or Ir; L = pyridine, perdeuteriopyridine or 4-methylpyridine; X = Cl or Br) with hydrogen nitrate and silver nitrate are described.     

Ruthenafuran Complexes Supported by the Bipyridine-Bis(diphenylphosphino)methane Ligand Set: Synthesis and Cytotoxicity Studies

Mononuclear and dinuclear Ru(II) complexes cis-[Ru(κ²-dppm)(bpy)Cl₂] (1), cis-[Ru(κ²-dppe)(bpy)Cl₂] (2) and [Ru₂(bpy)₂(μ-dpam)₂(μ-Cl)₂](Cl)₂ ([3](Cl)₂) were prepared from the reactions between cis(Cl), cis(S)-[Ru(bpy)(dmso-S)₂Cl₂] and diphosphine/diarsine ligands (bpy = 2,2′-bipyridine; dppm = 1,1-bis(diphenylphosphino)methane; dppe = 1,2-bis(diphenylphosphino)ethane; dpam = 1,1-bis(diphenylarsino)methane). While methoxy-substituted ruthenafuran [Ru(bpy)(κ²-dppe)(C^O)]⁺ ([7]⁺; C^O = anionic bidentate [C(OMe)CHC(Ph)O]⁻ chelate) was obtained as the only product in the reaction between 2 and phenyl ynone HC≡C(C=O)Ph in MeOH, replacing 2 with 1 led to the formation of both methoxy-substituted ruthenafuran [Ru(bpy)(κ²-dppm)(C^O)]⁺ ([4]⁺) and phosphonium-ring-fused bicyclic ruthenafuran [Ru(bpy)(P^C^O)Cl]⁺ ([5]⁺; P^C^O = neutral tridentate [(Ph)₂PCH₂P(Ph)₂CCHC(Ph)O] chelate). All of these aforementioned metallafuran complexes were derived from Ru(II)–vinylidene intermediates. The potential applications of these metallafuran complexes as anticancer agents were evaluated by in vitro cytotoxicity studies against cervical carcinoma (HeLa) cancer cell line. All the ruthenafuran complexes were found to be one order of magnitude more cytotoxic than cisplatin, which is one of the metal-based anticancer agents being widely used currently.     

A heteronuclear compound of ruthenium and silver containing bridging tris(pyridyl)methanoate ligands

The reaction of [{Ru(η⁶-C₆H₆)Cl(μ-Cl)}₂] with Py₃COH in ethanol results in the formation of the cation [Ru(η⁶-C₆H₆)(N,N′,O,-(C₅H₄N)₃CO)]⁺ which is isolated as its hexafluorphosphate salt 1. The cation acts as a ligand towards other transition metal ions. With Ag⁺ the hetero-trinuclear complex [{Ru(η⁶-C₆H₆)((C₅H₄N)₃CO)}₂Ag][PF₆]₃ 2 is formed, while reaction with [Pd(PhCN)₂Cl₂] gives the bimetallic [Ru(η⁶-C₆H₆)((C₅H₄N)₃CO)PdCl₂][PF₆] 3. Both compounds were fully characterised by spectroscopic methods and the trinuclear complex was additionally characterised by X-ray diffraction.     

Thermal and photochemical addition of alkyl and aryl halides to tetrakis(μ-pyrophosphito) diplatinum(II) tetraanion

Alkyl halides RI (R = Me, Et, n-Pr, i-Pr, n-pentyl, CF₃, CH₂I₂) undergo a thermal reaction with Pt₂(pop)₄⁴⁻ (pop = pyrophosphite) to give the axially substituted “lantern” complexes Pt₂(pop)₄RI⁴⁻. For R = Me, the pure complex can be isolated The solution structure has been characterized by a combination of ¹H, ¹³C, ³¹P and ¹⁹⁵Pt NMR spectroscopy. With the higher homologues, (R = Et, n-Pr, i- Pr, n-pentyl) the reaction gives a mixture of Pt₂(pop)₄RI⁴⁻ and Pt₂(pop)₄I₂⁴⁻. A radical pathway is proposed. Aryl halides ArX (X = Cl, Ar = Ph; X = Br, Ar = Ph, p-FC₆H₄, p-HOC₆H₄, p-CH₃OC₆H₄, p-HO₂CCH₄, p-CH₃C₆H₄; X = I, Ar = Ph) photochemically add to the triplet excited state Pt₂(pop)₄⁴⁻ to give Pt₂(pop)₄ArX⁴⁻. For the photochemical reaction with C₆F₅Br, CCl₄, CHCl₃, CH₂ClCO₂H, CH₂BrCO₂H and p-BrC₆H₄NH₃⁺ the product is the dihalo complex Pt₂(pop)₄X₂⁴⁻ (X = Cl, Br).     

Synthesis,crystallographic and spectroscopic characterization and magnetic properties of dimer and monomer ternary copper(II) complexes with sulfonamide derivatives and 1,10-phenanthroline. Nuclease activity by the oxidative mechanism

Three dinuclear and one mononuclear copper(II)-1,10-phenanthroline ternary complexes, [Cu(L1)(phen)(OH)]₂ (1), [Cu(L2)(phen)(OH)]₂·3H₂O (2), [Cu(L3)(phen)(OH)]₂ (3) and [Cu(L4)₂(phen)(H₂O)] (4), with thiadiazole sulfonamide derivative ligands: HL1 (N-(5-ethyl-1,3,4-thiadiazol-2-yl)naphthalene-1-sulfonamide), HL2 (N-(5-ethylthio)-1,3,4-thiadiazol-2-yl)-4-methylbenzenesulfonamide), HL3 (N-(5-ethyl-1,3,4-thiadiazol-2-yl)benzenesulfonamide) and HL4 (N-(5-ethyl-1,3,4-thiadiazol-2-yl)-4-methylbenzenesulfonamide) have been synthesized and characterized. In the four complexes each copper atom is five-coordinated. The structure of complexes 1, 2 and 3 consists of a dimeric unit with a C2 symmetry axis, where both coppers are bridged by two hydroxo anions. Magnetic measurements show that the dimer complexes are ferromagnetic according to the Cu–O–Cu angles. Cleavage experiments using pUC18 plasmid DNA in the presence of H₂O₂/ascorbic acid as an activating agent show that the title complexes are potent artificial chemical nucleases, the order of efficiency being 3 > 2 ∼ 1 > 4. Control cleavage experiments indicated that the dimer complexes are stronger artificial nucleases than the [Cu(phen)₂]²⁺ complex under the same experimental conditions, while the monomer 4 has a lower nuclease activity than the [Cu(phen)₂]²⁺ complex. The inhibition of the cleavage process in the presence of reactive oxygen intermediate scavengers suggests that the hydroxyl radical and the superoxide anion are reactive species for the breakage of the DNA strands.     

Ruthenium(II/III) bipyridine complexes incorporating thiol-based imine functions: Synthesis,spectroscopic and redox properties

A group of five new ruthenium(II) bipyridine heterochelates of the type [Ru^II(bpy)₂L]⁺ 1a–1e have been synthesized (bpy=2,2′-bipyridine; L=anionic form of the thiol-based imine ligands, HS–C₆H₄NC(H)C₆H₄(R) (R=OMe, Me, H, Cl, NO₂). The complexes 1a−1e are 1:1 conducting and diamagnetic. The complexes 1a−1e exhibit strong MLCT transitions in the visible region and intra-ligand transitions in the UV region. In acetonitrile solvent complexes show a reversible ruthenium(III)–ruthenium(II) couple in the range 0.2–0.4 V and irreversible ruthenium(III)→ruthenium(IV) oxidation in the range 1.15–1.73 V vs. SCE. Two successive bipyridine reductions are observed in the ranges −1.43 to −1.57 and −1.67 to −1.78 V vs. SCE. The complexes are susceptible to undergo stereoretentive oxidations to the trivalent ruthenium(III) congeners. The isolated one-electron paramagnetic ruthenium(III) complex, 1c⁺ exhibits weak rhombic EPR spectrum at 77 K (g₁=2.106, g₂=2.093, g₃=1.966) in 1:1 chloroform–toluene. The EPR spectrum of 1c⁺ has been analyzed to furnish values of distortion parameters (Δ=8988 cm⁻¹; V=0.8833 cm⁻¹) and energy of the expected ligand field transitions (ν₁=1028 nm and ν₂=1186 nm) within the t₂ shell. One of the ligand field transitions has been experimentally observed at 1265 nm.     

Synthesis,structure and electrochemical properties of a family of organoruthenium complexes

Reaction of N-(2′-hydroxyphenyl)benzaldimines (abbreviated in general as H₂L-R, where R stands for the para-substituent in the benzaldehyde fragment and H stands for the dissociable hydrogen atoms) with [Ru(PPh₃)₂(CO)₂Cl₂] affords a family of organoruthenium complexes of the type [Ru(PPh₃)₂(CO)(L-R)] where the N-(2′-hydroxyphenyl)benzaldimine ligand is coordinated to the metal center as tridentate C,N,O-donor. Structure of a representative complex has been determined by X-ray crystallography. All the [Ru(PPh₃)₂(CO)(L-R)] complexes are diamagnetic, and show characteristic ¹H NMR signals and moderately intense MLCT transitions in the visible region. Cyclic voltammetry of the [Ru(PPh₃)₂(CO)(L-R)] complexes shows a reversible Ru(II)–Ru(III) oxidation within 0.38–0.68 V versus SCE, followed by an irreversible oxidation of the coordinated benzaldimine ligand within 1.09–1.27 V versus SCE. An irreversible reduction of the coordinated benzaldimine ligand is also observed near −1.1 V versus SCE. Potential of the Ru(II)–Ru(III) oxidation is observed to be sensitive to the nature of para-substituent R.     

Ruthenium (II) polypyridyl complexes based on bipyridine and two novel diimine ligands with carrier-transporting unit: synthesis, photoluminescence and redox properties

A series of ruthenium (II) complexes, [Ru(bpy)₂L]X₂ (L = L1, L2; X = Cl⁻, PF₆⁻, SCN⁻), were synthesized based on bipyridine and two novel diimine ligands L1 and L2 (L1 = 1-(4-5′-phenyl-1,3,4-oxadiazolylphenyl)-2-pyridinyl-benzoimidazole, L2 = 1-(4-carbazolylphenyl)-2-pyridinylbenzimidazole); and the crystal structure of [Ru(bpy)₂L1]Cl₂ was also described. [Ru(bpy)₂(Pybm)]X₂ (Pybm = 2-(2-pyridine)benzimidazole) complexes were also prepared as reference samples. In the UV-vis absorption spectra there are one strong π → π* transition and two dπ (Ru) → π* transitions. By comparisons of photoluminescence properties between [Ru(bpy)₂L]X (L = L1, L2) and the reference complexes we find that the complexes with carrier-transporting groups of carbazole and oxadizole have the higher emission intensity and quantum efficiency. One reversible oxidation process in the range 0.80-1.00 V exists in each of the complexes which is assigned to the metal oxidation, [Ru(III)(bpy)₂L]²⁺ + e⁻?[Ru(II)(bpy)₂L]⁺.     

Reactions of 2-(arylazo)aniline with ruthenium substrates: Isolation, characterizations and reactivities of delocalized diazoketiminato and orthometallated Ru(II) chelates

Reactions of 2-(arylazo)aniline, HL-NH₂ [H represents the dissociable protons upon complexation and HL-NH₂ is p-RC₆H₄NNC₆H₄-NH₂; R = H for HL¹-NH₂; CH₃ for HL²-NH₂ and Cl for HL³-NH₂] with Ru(H)(CO)(PPh₃)₃Cl and Ru(CO)₃(PPh₃)₂ afforded products of compositions [(HL-NH)Ru(CO)Cl(PPh₃)₂] and [(L-NH)Ru(PPh₃)₂(CO)], respectively. All the complexes were characterized unequivocally. The X-ray structures of the complexes 4c and 5c have been determined. The cyclic volatammograms exhibited one reversible oxidative response in the range of 0.56–0.16 V versus SCE for [(L-NH)Ru(PPh₃)₂(CO)] and a quasi reversible oxidative response within 0.56–0.70 V versus SCE for [(HL-NH)Ru(CO)Cl(PPh₃)₂]. The conversion of ketones to corresponding alcohols has been studied in presence of newly synthesized ruthenium complexes.