mer‐Tri­chloro­tris(1,3‐thia­zole‐N)­ruthenium(III)

The potentially cytostatic title compound, mer‐[RuCl₃(C₃H₃NS)₃], is the first Ru^III–thz (thz is 1,3‐thia­zole) complex characterized via X‐ray diffraction and consists of discrete complex mol­ecules with an octahedral coordination sphere in which the metal centre is linked to three chloride ions and to three thz ligands through the N atoms. The Ru—Cl and Ru—N bond distances average 2.3462 (6) and 2.0851 (19) Å, respectively.     

Transfer hydrogenation of ketones catalysed by half‐sandwich (η6‐p‐cymene) ruthenium(II) complexes incorporating benzoylhydrazone ligands

Neutral half‐sandwich η⁶‐p ‐cymene ruthenium(II) complexes of general formula [Ru(η⁶‐p ‐cymene)Cl(L)] (HL = monobasic O, N bidendate benzoylhydrazone ligand) have been synthesized from the reaction of [Ru(η⁶‐p ‐cymene)(μ‐Cl)Cl]₂ with acetophenone benzoylhydrazone ligands. All the complexes have been characterized using analytical and spectroscopic (Fourier transform infrared, UV–visible, ¹H NMR, ¹³C NMR) techniques. The molecular structures of three of the complexes have been determined using single‐crystal X‐ray diffraction, indicating a pseudo‐octahedral geometry around the ruthenium(II) ion. All the ruthenium(II) arene complexes were explored as catalysts for transfer hydrogenation of a wide range of aromatic, cyclic and aliphatic ketones with 2‐propanol using 0.1 mol% catalyst loading, and conversions of up to 100% were obtained. Further, the influence of other variables on the transfer hydrogenation reaction, such as base, temperature, catalyst loading and substrate scope, was also investigated.     

Ferrocene based chiral binuclear η6‐benzene‐Ru(II)‐phosphinite complexes: Synthesis,characterization and catalytic activity in asymmetric reduction of ketones

In the present study, a series of chiral C₂‐symmetric ferrocenyl based binuclear η⁶‐benzene‐Ru(II) complexes bearing diphenylphosphinite and diisopropylphosphinite moieties have been synthesised. The new binuclear η⁶‐benzene‐Ru(II)‐phosphinite complexes were characterised based on nuclear magnetic resonance (¹H, ¹³C, ³¹P–NMR), FT‐IR spectroscopy and elemental analysis. Then, these complexes have been screened as catalytic precursors in the transfer hydrogenation of acetophenone with 2‐propanol as both the hydrogen source and solvent in the presence of KOH. The corresponding optically active secondary alcohols were obtained in excellent conversion rates between 96 and 99% and moderate to good enantioselectivities (up to 78% ee). The complex 5 was the most efficient catalyst among the four new complexes investigated herein.     

SBA‐15‐supported N‐coordinate ruthenium(II) materials bearing sulfonamide‐type ligands: Effect of ligand backbones on catalytic transfer hydrogenation of ketones and aldehydes

[RuLCl(p ‐cymene)] (L = N ‐arylsulfonylphenylenediamine) complexes ( 2 _{a – d} ) were synthesized from the reaction between [Ru(p ‐cymene)Cl₂]₂ and ligand. Additionally, SBA‐15–[RuLCl(p ‐cymene)] derived catalysts ( 3 _{a – d} ) were successfully immobilized onto mesoporous silica (SBA‐15) by an easily accessible approach. The structural elucidations of 2 _{a – d} and 3 _{a – d} were carried out with various methods such as ¹H NMR, ¹³C NMR and infrared spectroscopies, elemental analysis, thermogravimetric/differential thermal analysis, nitrogen adsorption–desorption and scanning electron microscopy/energy‐dispersive X‐ray analysis. The Ru(II) complexes and materials were found to be highly active and selective catalysts for the transfer hydrogenation (TH) reaction of aldehydes and ketones. The influence of various 1,2‐phenylenediamines on the reactivity of the catalysts (complexes or materials) was studied and the catalysts ( 2 _d and 3 _d ) with a 4,5‐dichlorophenylenediamine substituent showed the best activity (the maximum turnover frequencies are 2916 and 2154 h⁻¹ for TH of 4‐fluoroacetophenone, and 6000 and 4956 h⁻¹ for TH of 4‐chlorobenzaldehyde).     

Ruthenium(II) complexes derived from C2‐symmetric ferrocene‐based chiral bis(phosphinite) ligands: synthesis and catalytic activity towards the asymmetric reduction of acetophenones

Chiral secondary alcohols are very important building blocks and valuable synthetic intermediates both in organic synthesis and in the pharmaceutical industry for producing biologically active complex molecules. A series of new chiral Ru–phosphinite complexes ( 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ) were prepared from chiral C₂‐symmetric ferrocenyl phosphinites and corresponding chloro complex, [Ru(η⁶‐p‐cymene)(μ‐Cl)Cl]₂. The complexes were characterized using conventional spectroscopic methods. The binuclear complexes were tested as pre‐catalysts and were found to be good pre‐catalysts for the asymmetric transfer hydrogenation of substituted acetophenones in basic 2‐propanol at 82°C, providing the corresponding optically active alcohols with almost quantitative conversion and modest to high enantioselectivities (46–97%). Amongst the all complexes, complex 6 gave the highest ee of 97% in the reduction of 2‐methoxyacetophenone to (S)‐1‐(2‐methoxyphenyl)ethanol at 82°C. Copyright © 2015 John Wiley & Sons, Ltd.     

Ru–η6‐benzene–phosphine complex‐catalyzed transfer hydrogenation of ketones

Three Ru–η⁶‐benzene–phosphine complexes bearing tri‐(p‐methoxyphenyl)phosphine, triphenylphosphine and tri‐(p‐trifluoromethylphenyl)phosphine were synthesized and characterized by ³¹P{¹H} NMR, ¹H NMR, ¹³C{¹H} NMR and elemental analyses. Complex 1 was further identified by X‐ray crystallography. These complexes exhibit good to excellent activities for the transfer hydrogenation of ketones in refluxing 2‐propanol, and the highest turnover frequency (TOF) is up to 5940 h⁻¹. The effect of electronic factors of these complexes on the transfer hydrogenation of ketones reveals that the catalytic activity is promoted by electron‐donating phosphine and the catalyst stability is improved by electron‐withdrawing phosphine. Copyright © 2011 John Wiley & Sons, Ltd.     

2,3‐Di(2‐pyridyl)‐5‐phenylpyrazine: A NN‐CNN‐Type Bridging Ligand for Dinuclear Transition‐Metal Complexes

A new bridging ligand, 2,3‐di(2‐pyridyl)‐5‐phenylpyrazine (dpppzH), has been synthesized. This ligand was designed so that it could bind two metals through a NN‐CNN‐type coordination mode. The reaction of dpppzH with cis‐[(bpy)₂RuCl₂] (bpy=2,2′‐bipyridine) affords monoruthenium complex [(bpy)₂Ru(dpppzH)]²⁺ ( 12+ ) in 64 % yield, in which dpppzH behaves as a NN bidentate ligand. The asymmetric biruthenium complex [(bpy)₂Ru(dpppz)Ru(Mebip)]³⁺ ( 23+ ) was prepared from complex 12+ and [(Mebip)RuCl₃] (Mebip=bis(N‐methylbenzimidazolyl)pyridine), in which one hydrogen atom on the phenyl ring of dpppzH is lost and the bridging ligand binds to the second ruthenium atom in a CNN tridentate fashion. In addition, the RuPt heterobimetallic complex [(bpy)₂Ru(dpppz)Pt(C?CPh)]²⁺ ( 42+ ) has been prepared from complex 12+ , in which the bridging ligand binds to the platinum atom through a CNN binding mode. The electronic properties of these complexes have been probed by using electrochemical and spectroscopic techniques and studied by theoretical calculations. Complex 12+ is emissive at room temperature, with an emission λ_max=695 nm. No emission was detected for complex 23+ at room temperature in MeCN, whereas complex 42+ displayed an emission at about 750 nm. The emission properties of these complexes are compared to those of previously reported Ru and RuPt bimetallic complexes with a related ligand, 2,3‐di(2‐pyridyl)‐5,6‐diphenylpyrazine.     

Syntheses of 3‐arm and 4‐arm star‐branched polystyrene Ru(II) complexes by the click‐to‐chelate approach

Metal template synthesis is a useful methodology to make sophisticated macromolecular architectures because of the variety of metal ion coordination. To use metal template methodology, chelating functionalities should be introduced to macromolecules before complexation. In this article, we demonstrate the click‐to‐chelate approach to install chelating functionality to polystyrene (PS) and complexation with Ru(II) ions to form 3‐arm and 4‐arm star‐branched PS Ru(II) complexes. Azide‐terminated PS (PS‐N₃) was readily prepared by atom transfer radical polymerization using 1‐bromoethylbenzene as an initiator followed by substitution of bromine by an azide group. The Cu(I)‐catalyzed 1,3‐dipolar cycloaddition of PS‐N₃ with 2‐ethynylpyridine or 2,6‐diethynylpyridine affords 2‐(1H‐1,2,3‐triazol‐4‐yl)pyridine (PS‐tapy) or 2,6‐bis(1H‐1,2,3‐triazol‐4‐yl)pyridine (PS‐bitapy) ligands bearing one or two PS chains at the first‐position of the triazole rings. Ru(II) complexes of PS‐tapy and PS‐bitapy were prepared by conventional procedure. The number‐averaged molecular weights (M_ns) of these complexes were determined to be 6740 and 10,400, respectively, by size exclusion chromatography using PS standards. These M_n values indicated the formation of 3‐arm and 4‐arm star‐branched PS Ru(II) complexes [Ru(PS‐tapy)₃](PF₆)₂ and [Ru(PS‐bitapy)₂](PF₆)₂ on the basis of the M_n values of PS‐tapy (2090) and PS‐bitapy (4970). The structures of these complexes were also confirmed by UV–vis spectroscopy and X‐ray crystallography of the Ru(II) complexes [Ru(Bn‐tapy)₃](PF₆)₂ and [Ru(Bn‐bitapy)₂](PF₆)₂, which bear a benzyl group instead of a PS chain. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and characterization of new complexes of the type [Ru(CO)2Cl2 (2‐phenyl‐1,8‐naphthyridine‐kN) (2‐phenyl‐1,8‐naphthyridine‐kN′)]. Preliminary applications in homogeneous catalysis

Novel ruthenium (II) complexes were prepared containing 2‐phenyl‐1,8‐naphthyridine derivatives. The coordination modes of these ligands were modified by addition of coordinating solvents such as water into the ethanolic reaction media. Under these conditions 1,8‐naphthyridine (napy) moieties act as monodentade ligands forming unusual [Ru(CO)₂Cl₂(η¹‐2‐phenyl‐1,8‐naphthyridine‐ kN )(η¹‐2‐phenyl‐1,8‐naphthyridine‐kN′)] complexes. The reaction was reproducible when different 2‐phenyl‐1,8‐naphthyridine derivatives were used. On the other hand, when dry ethanol was used as the solvent we obtained complexes with napy moieties acting as a chelating ligand. The structures proposed for these complexes were supported by NMR spectra, and the presence of two ligands in the [Ru(CO)₂Cl₂(η¹‐2‐phenyl‐1,8‐naphthyridine‐ kN )(η¹‐2‐phenyl‐1,8‐naphthyridine‐kN′)] type complexes was confirmed using elemental analysis. All complexes were tested as catalysts in the hydroformylation of styrene showing moderate activity in N,N′‐dimethylformamide. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis,Characterization, and DNA‐Binding Properties of the Chiral Ruthenium(II) Complexes Δ‐ and Λ‐[Ru(bpy)2(dmppd)]2+ (dmppd = 10,12‐Dimethylpteridino[6,7‐f] [1,10]phenanthroline‐11,13(10H,12H)‐dione; bpy = 2,2′‐Bipyridine)

Two novel chiral ruthenium(II) complexes, Δ‐[Ru(bpy)₂(dmppd)]²⁺ and Λ‐[Ru(bpy)₂(dmppd)]²⁺ (dmppd = 10,12‐dimethylpteridino[6,7‐f] [1,10]phenanthroline‐11,13(10H,12H)‐dione, bpy = 2,2′‐bipyridine), were synthesized and characterized by elemental analysis, ¹H‐NMR and ES‐MS. The DNA‐binding behaviors of both complexes were studied by UV/VIS absorption titration, competitive binding experiments, viscosity measurements, thermal DNA denaturation, and circular‐dichroism spectra. The results indicate that both chiral complexes bind to calf‐thymus DNA in an intercalative mode, and the Δ enantiomer shows larger DNA affinity than the Λ enantiomer does. Theoretical‐calculation studies for the DNA‐binding behaviors of these complexes were carried out by the density‐functional‐theory method. The mechanism involved in the regulating and controlling of the DNA‐binding abilities of the complexes was further explored by the comparative studies of [Ru(bpy)₂(dmppd)]²⁺ and of its parent complex [Ru(bpy)₂(ppd)]²⁺ (ppd = pteridino[6,7‐f] [1,10]phenanthroline‐11,13 (10H,12H)‐dione).     

Chiral Bis(oxazoline) Ruthenium Complexes with Bipyridyl‐Type N‐Heteroaromatics: Comparative Stereochemical and Photochemical Characterization of their Λ‐ and Δ‐Diastereomeric Geminate Isomers

Diastereomeric geminate pairs of chiral bis(2‐oxazoline) ruthenium complexes with bipyridyl‐type N‐heteroaromatics, Λ‐ and Δ‐[Ru(L‐ L)₂(iPr‐biox)]²⁺ (iPr‐biox=(4S,4′S)‐4,4′‐diisopropyl‐2,2′‐bis(2‐oxazoline); L‐ L=2,2′‐bipyridyl (bpy) for 1 Λ and 1 Δ, 4,4′‐dimethyl‐2,2′‐bipyridyl (dmbpy) for 2 Λ and 2 Δ, and 1,10‐phenanthroline (phen) for 3 Λ and 3 Δ), were separated as BF₄ and PF₆ salts and were subjected to the comparative studies of their stereochemical and photochemical characterization. DFT calculations of 1 Λ and 1 Δ electronic configurations for the lowest triplet excited state revealed that their MO‐149 (HOMO) and MO‐150 (lower SOMO) characters are interchanged between them and that the phosphorescence‐emissive states are an admixture of a Ru‐to‐biox charge‐transfer state and an intraligand excited state within the iPr‐biox. Furthermore, photoluminescence properties of the two Λ,Δ‐diastereomeric series are discussed with reference to [Ru(bpy)₃]²⁺.     

Synthesis and photophysical properties of novel amphiphilic ruthenium (II) complexes containing 4,4′‐dialkylaminomethyl‐2,2′‐bipyridyl ligands

The synthesis of a number of new 2,2′‐bipyridine ligands functionalized with bulky amino side groups is reported. Three homoleptic polypyridyl ruthenium (II) complexes, [Ru(L)₃]²⁺ 2(PF₆^?), where L is 4,4′‐dioctylaminomethyl‐2,2′‐bipyridine (Ru4a), 4,4′‐didodecylaminomethyl‐2,2′‐bipyridine (Ru4b) and 4,4′‐dioctadodecylaminomethyl‐2,2′‐bipyridine (Ru4c), have been synthesized. These compounds were characterized and their photophysical properties examined. The electronic spectra of three complexes show pyridyl π → π* transitions in the UV region and metal‐to‐ligand charge transfer bands in the visible region. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis,Characterization, and DNA Interaction Studies of the Ruthenium(II) Complexes [Ru(bpy)2(ipbp)]2+ and [Ru(ipbp)(phen)2]2+ (ipbp=3‐(1H‐Imidazo[4,5‐f][1,10]phenanthrolin‐2‐yl)‐4H‐1‐benzopyran‐2‐one; bpy=2,2′‐Bipyridine; phen=1,10‐Phenanthroline)

A novel ligand 3‐(1H‐imidazo[4,5‐f][1,10]phenanthrolin‐2‐yl)‐4H‐1‐benzopyran‐4‐one (ipbp) and its ruthenium(II) complexes [Ru(bpy)₂(ipbp)]²⁺ ( 1 ) and [Ru(ipbp)(phen)₂]²⁺ ( 2 ) (bpy=2,2′‐bipyridine, phen=1,10‐phenanthroline) were synthesized and characterized by elemental analysis and mass, ¹H‐NMR, and electronic‐absorption spectroscopy. The electrochemical behavior of the complexes was studied by cyclic voltammetry. The DNA‐binding behavior of the complexes was investigated by spectroscopic methods and viscosity measurements. The results indicate that complexes 1 and 2 bind with calf‐thymus DNA in an intercalative mode. In addition, 1 and 2 promote cleavage of plasmid pBR 322 DNA from the supercoil form I to the open circular form II upon irradiation.     

Synthesen und Strukturen von Bis(4,4′‐t‐butyl‐2,2′‐bipyridin)‐Ruthenium(II)‐Komplexen mit funktionellen Derivaten des Tetramethyl‐bibenzimidazols

Syntheses and Structures of Bis(4,4′‐t‐butyl‐2,2′‐bipyridine) Ruthenium(II) Complexes with functional Derivatives of Tetramethyl‐bibenzimidazole [(tbbpy)₂RuCl₂] reacts with dinitro‐tetramethylbibenzimidazole ( A ) in DMF to form the complex [(tbbpy)₂Ru( A )](PF₆)₂ ( 1a ) (tbbpy: bis(4,4′‐t‐butyl)‐2,2′bipyridine). Exchange of the two PF₆^? anions by a mixture of tetrafluor‐terephthalat/tetrafluor‐terephthalic acid results in the formation of 1b in which an extended hydrogen‐bonded network is formed. According to the ¹H NMR spectra and X‐ray analyses of both 1a and 1b , the two nitro groups of the bibenzimidazole ligand are situated at the periphery of the complex in cis position to each other. Reduction of the nitro groups in 1a with SnCl₂/HCl results in the corresponding diamino complex 2 which is a useful starting product for further functionalization reactions. Substitution of the two amino groups in 2 by bromide or iodide via Sandmeyer reaction results in the crystalline complexes [(tbbpy)₂Ru( C )](PF₆)₂ and [(tbbpy)₂Ru( D )](PF₆)₂ ( C : dibromo‐tetrabibenzimidazole, D : diiodo‐tetrabibenzimidazole). Furthermore, 2 readily reacts with 4‐t‐butyl‐salicylaldehyde or pyridine‐2‐carbaldehyde under formation of the corresponding Schiff base Ru^II complexes 5 and 6 . ¹H NMR spectra show that the substituents (NH₂, Br, I, azomethines) in 2 ‐ 6 are also situated in peripheral positions, cis to each other. The solid state structure of both 2 , and 3 , determined by X‐ray analyses confirm this structure. In addition, the X‐ray diffraction analyses of single crystals of the complexes [(tri‐t‐butyl‐terpy)(Cl)Ru( A )] ( 7 ) and [( A )PtCl₂] ( 8 ) display also that the nitro groups in these complexes are in a cis‐arrangement.     

Quinine‐Derived Imidazolidin‐2‐imine Ligands: Synthesis,Coordination Chemistry,and Application in Catalytic Transfer Hydrogenation

Two new optically active bidentate N,N‐ligands, DMIQCI ( 3a ) and DMIQCD ( 3b ), containing a quinuclidine core and an imidazolidin‐2‐imine unit, were synthesized. The reaction of these ligands with [(η⁵‐C₅Me₅)RuCl]₄ afforded the brick‐red ruthenium(II) complexes [(η⁵‐C₅Me₅)Ru(DMIQCI)Cl] ( 4 ) and [(η⁵‐C₅Me₅)Ru(DMIQCD)Cl] ( 5 ), which were used as catalysts in the transfer hydrogenation of acetophenone in boiling 2‐propanol. The reactions of 3a and 3b with [(COD)PdCl₂] (COD = 1,5‐cycloocta‐diene) and with [(DME)NiBr₂] (DME = 1,2‐dimethoxyethane) afforded the square‐planar palladium(II) complexes [(DMIQCI)PdCl₂] ( 7 ) and [(DMIQCD)PdCl₂] ( 8 ) or the tetrahedral nickel(II) complexes [(DMIQCI)NiBr₂] ( 9 ) and [(DMIQCD)NiBr₂] ( 10 ), respectively. The X‐ray crystal structures of 4 , 7 , 9· THF, and 10 are reported.     

Chiral η6‐Arene/N‐Tosylethylenediamine–Ruthenium(II) Complexes: Solution Behavior and Catalytic Activity for Asymmetric Hydrogenation

Aromatic ketones are enantioseletively hydrogenated in alcohols containing [RuX{(S,S)‐Tsdpen}(η⁶‐p‐cymene)] (Tsdpen=TsNCH(C₆H₅)CH(C₆H₅)NH₂; X=TfO, Cl) as precatalysts. The corresponding Ru hydride (X=H) acts as a reducing species. The solution structures and complete spectral assignment of these complexes have been determined using 2D NMR (¹H‐¹H DQF‐COSY, ¹H‐¹³C HMQC, ¹H‐¹⁵N HSQC, and ¹H‐¹⁹F HOESY). Depending on the nature of the solvents and conditions, the precatalysts exist as a covalently bound complex, tight ion pair of [Ru⁺(Tsdpen)(cymene)] and X^?, solvent‐separated ion pair, or discrete free ions. Solvent effects on the NH₂ chemical shifts of the Ru complexes and the hydrodynamic radius and volume of the Ru⁺ and TfO^? ions elucidate the process of precatalyst activation for hydrogenation. Most notably, the Ru triflate possessing a high ionizability, substantiated by cyclic voltammetry, exists in alcoholic solvents largely as a solvent‐separated ion pair and/or free ions. Accordingly, its diffusion‐derived data in CD₃OD reflect the independent motion of [Ru⁺(Tsdpen)(cymene)] and TfO^?. In CDCl₃, the complex largely retains the covalent structure showing similar diffusion data for the cation and anion. The Ru triflate and chloride show similar but distinct solution behavior in various solvents. Conductivity measurements and catalytic behavior demonstrate that both complexes ionize in CH₃OH to generate a common [Ru⁺(Tsdpen)(cymene)] and X^?, although the extent is significantly greater for X=TfO^?. The activation of [RuX(Tsdpen)(cymene)] during catalytic hydrogenation in alcoholic solvent occurs by simple ionization to generate [Ru⁺(Tsdpen)(cymene)]. The catalytic activity is thus significantly influenced by the reaction conditions.     

Two‐Photon Chemistry in Ruthenium 2,2′‐Bipyridyl‐Functionalized Single‐Wall Carbon Nanotubes

Ruthenium polypyridyl complexes are widely used as light harvesters in dye‐sensitized solar cells. Since one of the potential applications of single‐wall carbon nanotubes (SWCNTs) and their derived materials is their use as active components in organic and hybrid solar cells, the study of the photochemistry of SWCNTs with tethered ruthenium polypyridyl complexes is important. A water‐soluble ruthenium tris(bipyridyl) complex linked through peptidic bonds to SWCNTs (Ru‐SWCNTs) was prepared by radical addition of thiol‐terminated SWCNT to a terminal C?C double bond of a bipyridyl ligand of the ruthenium tris(bipyridyl) complex. The resulting macromolecular Ru‐SWCNT (≈500 nm, 15.6 % ruthenium complex content) was water‐soluble and was characterized by using TEM, thermogravimetric analysis, chemical analysis, and optical spectroscopy. The emission of Ru‐SWCNT is 1.6 times weaker than that of a mixture of [Ru(bpy)₃]²⁺ and SWCNT of similar concentration. Time‐resolved absorption optical spectroscopy allows the detection of the [Ru(bpy)₃]²⁺‐excited triplet and [Ru(bpy)₃]⁺. The laser flash studies reveal that Ru‐SWCNT exhibits an unprecedented two‐photon process that is enabled by the semiconducting properties of the SWCNT. Thus, the effect of the excitation wavelength and laser power on the transient spectra indicate that upon excitation of two [Ru(bpy)₃]²⁺ complexes of Ru‐SWCNT, a disproportionation process occurs leading to delayed formation of [Ru(bpy)₃]⁺ and the performance of the SWCNT as a semiconductor. This two‐photon delayed [Ru(bpy)₃]⁺ generation is not observed in the photolysis of [Ru(bpy)₃]³⁺; SWCNT acts as an electron wire or electron relay in the disproportionation of two [Ru(bpy)₃]²⁺ triplets in a process that illustrates that the SWCNT plays a key role in the process. We propose a mechanism for this two‐photon disproportionation compatible with i) the need for high laser flux, ii) the long lifetime of the [Ru(bpy)₃]²⁺ triplets, iii) the semiconducting properties of the SWNT, and iv) the energy of the HOMO/LUMO levels involved.     

Aqua­bis(3‐meth­oxy‐2‐pyridonato)­(2,2′:6′,2′′‐terpyridine)ruthenium(II)–acetonitrile–water (1/1/1)

The title compound, [Ru(C₆H₆NO₂)₂(C₁₅H₁₁N₃)(H₂O)]·CH₃CN·H₂O, is a transfer hydrogenation catalyst supported by nitro­gen‐donor ligands. This octa­hedral Ru^II complex features rare monodentate coordination of 3‐meth­oxy‐2‐pyridonate ligands and inter­ligand S(6)S(6) hydrogen bonding. Comparison of the title complex with a structural analog with unsubstituted 2‐pyridonate ligands reveals subtle differences in the orientation of the ligand planes.     

Reactivity Studies of η5‐ Indenyl and η5‐Cp* Ruthenium(II) Complexes towards some Polypyridyl Ligands

The reaction of [(η⁵‐L³)Ru(PPh₃)₂Cl], where; L³ = C₉H₇ ( 1 ), C₅Me₅ (Cp*) ( 2 ) with acetonitrile in the presence of [NH₄][PF₆] yielded cationic complexes [(η⁵‐L³)Ru(PPh₃)₂(CH₃CN)][PF₆]; L³= C₉H₇ ([3]PF₆) and L³ = C₅Me₅ ([4]PF₆), respectively. Complexes [3]PF₆ and [4]PF₆ reacts with some polypyridyl ligands viz, 2,3‐bis (α‐pyridyl) pyrazine (bpp), 2,3‐bis (α‐pyridyl) quinoxaline (bpq) yielding the complexes of the formulation [(η⁵‐L³)Ru(PPh₃)(L²)]PF₆ where; L³ = C₉H₇, L² = bpp, ([5]PF₆), L³ = C₉H₇, L² = bpq, ([6]PF₆); L³ = C₅Me₅, L² = bpp, ([7]PF₆) and bpq, ([8]PF₆), respectively. However reaction of [(η⁵‐C₉H₇)Ru(PPh₃)₂(CH₃CN)][PF₆] ([3]PF₆) with the sterically demanding polypyridyl ligands, viz. 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine (tptz) or tetra‐2‐pyridyl‐1,4‐pyrazine (tppz) leads to the formation of unexpected complexes [Ru(PPh₃)₂(L²)(CH₃CN)][PF₆]₂; L² = tppz ([9](PF₆)₂), tptz ([11](PF₆)₂) and [Ru(PPh₃)₂(L²)Cl][PF₆]; L² = tppz ([10]PF₆), tptz ([12]PF₆). The complexes were isolated as their hexafluorophosphate salts. They have been characterized on the basis of micro analytical and spectroscopic data. The crystal structures of the representative complexes were established by X‐ray crystallography.     

(Nitro‐κN)[2‐(phenyldiazenyl‐κN2)pyridine‐κN](2,2′:6′,2′′‐terpyridine‐κ3N)ruthenium(II) tetrafluoroborate

The Ru—N bond distances in the title complex, [Ru(NO₂)(C₁₁H₉N₃)(C₁₅H₁₁N₃)]BF₄ or [Ru(NO₂)(tpy)(azpy)]BF₄, [tpy is 2,2′:6′,2′′‐ter­pyridine and azpy is 2‐(phenyl­azo)­pyridine], are Ru—N_py 2.063 (4), Ru—N_azo 2.036 (4), Ru—N_nitro 2.066 (3) Å, and Ru—N_tpy 2.082 (4), 1.982 (3) and 2.074 (4) Å. The azo N atom is trans to the nitro group. The azo N=N bond length is 1.265 (5) Å, which is the shortest found in such complexes to date. This indicates a multiple bond between Ru and the N atom of the nitro group, and π‐­backbonding [dπ(Ru) π*(azo)] is decreased.