Improved Synthesis of the [Ru(η6‐p‐cymene)Cl3] Anion: Facile Isolation under Mild Conditions

Reaction of [Ru(η⁶‐p‐cymene)Cl₂]₂ with two equivalents of [Ph₄P][Cl] in CH₂Cl₂ yields [Ph₄P][Ru(η⁶‐p‐cymene)Cl₃], containing a trichlororuthenate(II) anion. In solution, an equilibrium between the product and [Ru(η⁶‐p‐cymene)Cl₂]₂ is observed, which in CDCl₃ is nearly completely shifted to the dimer, whereas in CD₂Cl₂ essentially a 1:1‐mixture of the two ruthenium species is present. Crystallization from CH₂Cl₂/pentane yielded two different crystals, which were identified by X‐ray analysis as [Ph₄P][Ru(η⁶‐p‐cymene)Cl₃] and [Ph₄P][Ru(η⁶‐p‐cymene)Cl₃]·CH₂Cl₂.     

Selenoquinones Stabilized by Ruthenium(II) Arene Complexes: Synthesis,Structure, and Cytotoxicity

A new series of monoselenoquinone and diselenoquinone π complexes, [(η⁶‐p‐cymene)Ru(η⁴‐C₆R₄SeE)] (R=H, E=Se ( 6 ); R=CH₃, E=Se ( 7 ); R=H, E=O ( 8 )), as well as selenolate π complexes [(η⁶‐p‐cymene)Ru(η⁵‐C₆H₃R₂Se)][SbF₆] (R=H ( 9 ); R=CH₃ ( 10 )), stabilized by arene ruthenium moieties were prepared in good yields through nucleophilic substitution reactions from dichlorinated‐arene and hydroxymonochlorinated‐arene ruthenium complexes [(η⁶‐p‐cymene)Ru(C₆R₄XCl)][SbF₆]₂ (R=H, X=Cl ( 1 ); R=CH₃, X=Cl ( 2 ); R=H, X=OH ( 3 )) as well as the monochlorinated π complexes [(η⁶‐p‐cymene)Ru(η⁵‐C₆H₃R₂Cl)][SbF₆]₂ (R=H ( 4 ); R=CH₃ ( 5 )). The X‐ray crystallographic structures of two of the compounds, [(η⁶‐p‐cymene)Ru(η⁴‐C₆Me₄Se₂)] ( 7 ) and [(η⁶‐p‐cymene)Ru(η⁴‐C₆H₄SeO)] ( 8 ), were determined. The structures confirm the identity of the target compounds and ascertain the coordination mode of these unprecedented ruthenium π complexes of selenoquinones. Furthermore, these new compounds display relevant cytotoxic properties towards human ovarian cancer cells.     

Novel cyclohexyl‐based aminophosphine ligands and use of their Ru(II) complexes in transfer hydrogenation of ketones

Two new aminophosphines – furfuryl‐(N‐dicyclohexylphosphino)amine, [Cy₂PNHCH₂–C₄H₃O] ( 1 ) and thiophene‐(N‐dicyclohexylphosphino)amine, [Cy₂PNHCH₂–C₄H₃S] ( 2 ) – were prepared by the reaction of chlorodicyclohexylphosphine with furfurylamine and thiophene‐2‐methylamine. Reaction of the aminophosphines with [Ru(η⁶‐p‐cymene)(μ‐Cl)Cl]₂ or [Ru(η⁶‐benzene)(μ‐Cl)Cl]₂ gave corresponding complexes [Ru(Cy₂PNHCH₂–C₄H₃O)(η⁶‐p‐cymene)Cl₂] ( 1a ), [Ru(Cy₂PNHCH₂–C₄H₃O)(η⁶‐benzene)Cl₂] ( 1b ), [Ru(Cy₂PNHCH₂–C₄H₃S)(η⁶‐p‐cymene)Cl₂] ( 2a ) and [Ru(Cy₂PNHCH₂–C₄H₃S)(η⁶‐benzene)Cl₂] ( 2b ), respectively, which are suitable catalyst precursors for the transfer hydrogenation of ketones. In particular, [Ru(Cy₂PNHCH₂–C₄H₃S)(η⁶‐benzene)Cl₂] acts as a good catalyst, giving the corresponding alcohols in 98–99% yield in 30 min at 82 °C (up to time of flight ≤ 588 h^?1). Copyright © 2014 John Wiley & Sons, Ltd.     

Enhanced Anion Binding from Unusual Coordination Modes of Bis(thiourea) Ligands in Platinum Group Metal Complexes

Treatment of a range of bis(thiourea) ligands with inert organometallic transition‐metal ions gives a number of novel complexes that exhibit unusual ligand binding modes and significantly enhanced anion binding ability. The ruthenium(II) complex [Ru(η⁶‐p‐cymene)(κS,S′,N‐ L³ ?H)]⁺ ( 2 b ) possesses juxtaposed four‐ and seven‐membered chelate rings and binds anions as both 1:1 and 2:1 host guest complexes. The pyridyl bis(thiourea) complex [Ru(η⁶‐p‐cymeme)(κS,S′,N_py‐ L⁴ )]²⁺ ( 4 ) binds anions in both 1:1 and 1:2 species, whereas the free ligand is ineffective because of intramolecular NH???N hydrogen bonding. Novel palladium(II) complexes with nine‐ and ten‐membered chelate rings are also reported.     

Synthesis of Imines via Reactions of Benzyl Alcohol with Amines Using Half‐Sandwich (η6‐p‐cymene) Ruthenium(II) Complexes Stabilised by 2‐aminofluorene Derivatives

A new class of half‐sandwich (η⁶‐p‐cymene) ruthenium(II) complexes supported by 2‐aminofluorene derivatives [Ru(η⁶‐p‐cymene)(Cl)(L)] ( L  = 2‐(((9H‐fluoren‐2‐yl)imino)methyl)phenol ( L ¹ ), 2‐(((9H‐fluoren‐2‐yl)imino)methyl)‐3‐methoxyphenol ( L ² ), 1‐(((9H‐fluoren‐2‐yl)imino)methyl)naphthalene‐2‐ol ( L ³ ) and N‐((1H‐pyrrol‐2‐yl)methylene)‐9H‐fluorene‐2‐amine ( L ⁴ )) were synthesized. All compounds were fully characterized by analytical and spectroscopic techniques (IR, UV–Vis, NMR) and also by mass spectrometry. The solid state molecular structures of the complexes [Ru(η⁶‐p‐cymene)(Cl)(L²)], [Ru(η⁶‐p‐cymene)(Cl)(L³)] and [Ru(η⁶‐p‐cymene)(Cl)(L⁴)] revealed that the 2‐aminofluorene and p‐cymene moieties coordinate to ruthenium(II) in a three‐legged piano‐stool geometry. The synthesized complexes were used as catalysts for the dehydrogenative coupling of benzyl alcohol with a range of amines (aliphatic, aromatic and heterocyclic). The reactions were carried out under thermal heating, ultrasound and microwave assistance, using solvent or solvent free conditions, and the catalytic performance was optimized regarding the solvent, the type of base, the catalyst loading and the temperature. Moderately high to very high isolated yields were obtained using [Ru(η⁶‐p‐cymene)(Cl)(L⁴)] at 1 mol%. In general, microwave irradiation produced better yields than the other two techniques irrespective of the nature of the substituents.     

Identification of the Structural Determinants for Anticancer Activity of a Ruthenium Arene Peptide Conjugate

Organometallic Ru(arene)–peptide bioconjugates with potent in vitro anticancer activity are rare. We have prepared a conjugate of a Ru(arene) complex with the neuropeptide [Leu⁵]‐enkephalin. [Chlorido(η⁶‐p‐cymene)(5‐oxo‐κO‐2‐{(4‐[(N‐tyrosinyl‐glycinyl‐glycinyl‐phenylalanyl‐leucinyl‐NH₂)propanamido]‐1H‐1,2,3‐triazol‐1‐yl)methyl}‐4H‐pyronato‐κO)ruthenium(II)] ( 8 ) shows antiproliferative activity in human ovarian carcinoma cells with an IC₅₀ value as low as 13 μM , whereas the peptide or the Ru moiety alone are hardly cytotoxic. The conjugation strategy for linking the Ru(cym) (cym=η⁶‐p‐cymene) moiety to the peptide involved N‐terminal modification of an alkyne‐[Leu⁵]‐enkephalin with a 2‐(azidomethyl)‐5‐hydroxy‐4H‐pyran‐4‐one linker, using Cu^I‐catalyzed alkyne–azide cycloaddition (CuAAC), and subsequent metallation with the Ru(cym) moiety. The ruthenium‐bioconjugate was characterized by high resolution top‐down electrospray ionization mass spectrometry (ESI‐MS) with regard to peptide sequence, linker modification and metallation site. Notably, complete sequence coverage was obtained and the Ru(cym) moiety was confirmed to be coordinated to the pyronato linker. The ruthenium‐bioconjugate was analyzed with respect to cytotoxicity‐determining constituents, and through the bioconjugate models [{2‐(azidomethyl)‐5‐oxo‐κO‐4H‐pyronato‐κO}chloride (η⁶‐p‐cymene)ruthenium(II)] ( 5 ) and [chlorido(η⁶‐p‐cymene){5‐oxo‐κO‐2‐([(4‐(phenoxymethyl)‐1H‐1,2,3‐triazol‐1‐yl]methyl)‐4H‐pyronato‐κO}ruthenium(II)] ( 6 ) the Ru(cym) fragment with a triazole‐carrying pyronato ligand was identified as the minimal unit required to achieve in vitro anticancer activity.     

Preparation of Organometallic Ruthenium–Arene–Diaminotriazine Complexes as Binding Agents to DNA

The reactions of two diaminotriazine ligands 2,4‐diamino‐6‐(2‐pyridyl)‐1,3,5‐triazine (2‐pydaT) and 6‐phenyl‐2,4‐diamino‐1,3,5‐triazine (PhdaT) with ruthenium–arene precursors led to a new family of ruthenium(II) compounds that were spectroscopically characterized. Four of the complexes were cationic, with the general formula [(η⁶‐arene)Ru(κ²‐N,N‐2‐pydaT)Cl]X (X=BF₄, TsO; arene=p‐cymene: 1.BF4 , 1.TsO arene=benzene: 2.BF4 , 2.TsO ). The neutral cyclometalated complex [(η⁶‐p‐cymene)Ru(κ²‐C,N‐PhdaT*)Cl] ( 3 ) was also isolated. The structures of complexes 2.BF4 and 3.H2O were determined by X‐ray diffraction. Complex 1.BF4 underwent a partial reversible‐aquation process in water. UV/Vis and NMR spectroscopic measurements showed that the reaction was hindered by the addition of NaCl and was pH‐controlled in acidic solution. At pH 7.0 (sodium cacodylate) Ru–Cl complex 1.BF4 was the only species present in solution, even at low ionic strength. However, in alkaline medium (KOH), complex 1.BF4 underwent basic hydrolysis to afford a Ru–OH complex ( 5 ). Fluorimetric studies revealed that the interaction of complex 1.BF4 with DNA was not straightforward; instead, its main features were closely linked to ionic strength and to the [DNA]/complex ratio. The bifunctional complex 1.BF4 was capable of interacting concurrently through both its p‐cymene and 2‐pydaT groups. Cytotoxicity and genotoxicity studies showed that, contrary to the expected behavior, the complex species was biologically inactive; the formation of a Ru–OH complex could be responsible for such behavior.     

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.     

A modular design of metal catalysts for the transfer hydrogenation of aromatic ketones

The ability of transition metal catalysts to add or remove hydrogen from organic substrates by transfer hydrogenation is a valuable synthetic tool. Towards a series of novel metal complexes with a P―NH ligand, [Ph₂PNHCH₂―C₄H₃O] derived from furfurylamine were synthesized. Reaction of [Ph₂PNHCH₂―C₄H₃O] 1 with [Ru(η⁶‐p‐cymene)(μ‐Cl)Cl]₂, [Ru(η⁶‐benzene)(μ‐Cl)Cl]₂, [Rh(μ‐Cl)(cod)]₂ and [Ir(η⁵‐C₅Me₅)(μ‐Cl)Cl]₂ gave a range of new monodentate complexes [Ru(Ph₂PNHCH₂―C₄H₃O)(η⁶‐p‐cymene)Cl₂] 2 , [Ru(Ph₂PNHCH₂―C₄H₃O)(η⁶‐benzene)Cl₂] 3 , [Rh(Ph₂PNHCH₂‐C₄H₃O)(cod)Cl] 4 , and [Ir(Ph₂PNHCH₂‐C₄H₃0)(η⁵‐C₅Me₅)Cl₂] 5 , respectively. All new complexes were fully characterized by analytical and spectroscopic methods. ³¹P‐{¹H} NMR, distortionless enhancement by polarization transfer (DEPT) or ¹H‐¹³C heteronuclear correlation (HETCOR) experiments were used to confirm the spectral assignments. Following activation by KOH, compounds 1 , 2 , 3 , 4 catalyzed the transfer hydrogenation of acetophenone derivatives to 1‐phenylethanol derivatives in the presence of iso‐PrOH as the hydrogen source. Notably [Ru(Ph₂PNHCH₂‐C₄H₃O)(η⁶‐benzene)Cl₂] 3 acts as an excellent catalyst, giving the corresponding alcohols in 98–99% yield in 20 min at 82°C (time of flight ≤ 297 h^?1) for the transfer hydrogenation reaction in comparison to analogous rhodium or iridium complexes. Copyright © 2012 John Wiley & Sons, Ltd.     

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.     

Biological and catalytic evaluation of Ru(II)‐p‐cymene complexes of Schiff base ligands: Impact of ligand appended moiety on photo‐induced DNA and protein cleavage,cytotoxicity and C‐H activation

Two organometallic Ru(II)‐p‐cymene complexes of the type [Ru(η⁶‐p‐cymene)(L)Cl]PF₆ 1 and 2 , where L is N,N‐bis(4‐isopropylbenzylidene)ethane‐1,2‐diamine (bien, L1 ) or N,N‐bis (pyren‐2‐ylmethylene)ethane‐1,2‐diamine (bpen, L2 ) have been prepared and characterized well. Because of appended pyrenyl groups in coordinated bpen ligand, the complex 2 exhibits higher DNA and protein binding than complex 1 in which isopropylbenzyl groups are incorporated. Interestingly, the luminescent characteristic complex 2 is unique in displaying DNA cleavage after light activation by UVA light at 365 nm through oxygen dependent mechanism. AFM analysis attests the photo‐induced DNA fragmentation ability of complex 2 . Also, the complex 2 cleaves the protein after light exposure in a non‐specific manner suggesting that it can act as a protein photo cleaving agent. In contrast to the trend of DNA and protein interaction of complexes, the complex 1 exhibits cytotoxic activity against human breast carcinoma ( MCF‐7 ) and liver carcinoma ( HepG2 ) with potency higher than that of complex 2 due to enhanced hydrophobicity of isopropyl groups present in p‐cymene and bien ligands. Indeed, complex 2 is inactive against MCF‐7 and HepG2 cancer cell lines even up to 200 μM concentration. The AO/EB staining assay reveals that the complex 1 is able to induce late apoptotic mode of cell death in breast cancer cells, which is further confirmed by inter‐nucleosomal DNA cleavage. Furthermore, the complexes 1 and 2 are evaluated for their catalytic activities and found to be working well for the β‐carboline directed C–H arylation to afford the desired products in good yield (40–47%).     

Synthesis and Cytotoxicity of Arene‐Ru Compounds Containing 4‐Nitroaniline or 2‐Halogenated 4‐Nitroaniline

The compounds [(η⁶‐p‐cymene)RuCl₂(4‐nitroaniline)] and [(η⁶‐p‐cymene)RuCl₂(2‐halogen‐4‐nitroaniline)] were synthesized and characterized by various means. The [(η⁶‐p‐cymene)RuCl₂(4‐nitroaniline)] and [(η⁶‐p‐cymene)RuCl₂(2‐fluoro‐4‐nitroaniline)] compounds were determined by X‐ray diffraction, appearing in a distorted piano‐stool type of arrangement with similar bond lengths and angles around the ruthenium. The compounds exhibited moderate to strong in vitro cytotoxicity against A549 and MCF‐7 human cancer cells. Substitution of heavy halogen atom on the ortho position of para‐nitroaniline weakened the cytotoxicity against both of MCF‐7 and A549, except the cases of fluorine substitution for hydrogen atom regarding A549 and bromine substitution for chlorine atom regarding MCF‐7, which showed minor deviation.     

Synthesis,structure determination and chemoselective catalytic studies of amino acids complexes of osmium(II)

The two new half sandwich amino acids complexes of osmium, i.e. [Os(η6‐p‐cymene)(κ1‐N‐(rac)‐phenylglycine methylester)Cl₂] ( A ) and [Os(η6‐p‐cymene)(κ1‐N,N′‐(S)‐phenylalanineamido)Cl] ( B ) have been synthesized and employed for chemoselective reduction of ketones (nine α,β‐unsaturated ketones and three saturated ketones). The complexes were characterized by spectroscopic as well as analytical methods; their solid structures were confirmed by single‐crystal X‐ray analysis. Both of the osmium complexes catalyze the reduction of α,β‐unsaturated ketones to saturated ketones via isomerization of the initially produced allylic alcohols. The reducible substrates were studied to obtain information on the steric and electronic factors which may affect the interaction of the substrate with the metal center and, thus, control the selectivity of the hydrogen‐transfer reductions. Copyright © 2008 John Wiley & Sons, Ltd.     

A μ‐chloro‐bridged dinuclear ruthenium complex with 9H‐carbazole: the formation of one‐dimensional linear chains of star‐shaped edge‐fused rings

The title complex, di‐μ‐chloro‐bis­[chloro­(η⁶‐p‐cymene)ruthenium(II)]–9H‐carbazole (1/2), [Ru₂Cl₄(C₁₀H₁₄)₂]·2C₁₂H₉N, is composed of one [RuCl₂(η⁶‐p‐cymene)]₂ and two 9H‐carbazole mol­ecules. There are one‐half of a dinuclear complex and one 9H‐carbazole mol­ecule per asymmetric unit. In the dinuclear complex, each of the two crystallographically equivalent Ru atoms is in a pseudo‐tetra­hedral environment, coordinated by a terminal Cl atom, two bridging Cl atoms and the aromatic hydro­carbon, which is linked in a η⁶ manner; the Ru⋯Ru separation is 3.688 (3) Å. The title complex has a crystallographic centre of symmetry located at the mid‐point of the Ru⋯Ru line. Inter­molecular N—H⋯Cl and π–π stacking inter­actions are observed. These inter­actions form a four‐pointed star‐shaped ring and one‐dimensional linear chains of edge‐fused rings running parallel to the [100] direction, which stabilize the crystal packing.     

Highly Efficient Redox Isomerisation of Allylic Alcohols Catalysed by Pyrazole‐Based Ruthenium(IV) Complexes in Water: Mechanisms of Bifunctional Catalysis in Water

The catalytic activity of ruthenium(IV) ([Ru(η³:η³‐C₁₀H₁₆)Cl₂L]; C₁₀H₁₆=2,7‐dimethylocta‐2,6‐diene‐1,8‐diyl, L=pyrazole, 3‐methylpyrazole, 3,5‐dimethylpyrazole, 3‐methyl‐5‐phenylpyrazole, 2‐(1H‐pyrazol‐3‐yl)phenol or indazole) and ruthenium(II) complexes ([Ru(η⁶‐arene)Cl₂(3,5‐dimethylpyrazole)]; arene=C₆H₆, p‐cymene or C₆Me₆) in the redox isomerisation of allylic alcohols into carbonyl compounds in water is reported. The former show much higher catalytic activity than ruthenium(II) complexes. In particular, a variety of allylic alcohols have been quantitatively isomerised by using [Ru(η³:η³‐C₁₀H₁₆)Cl₂(pyrazole)] as a catalyst; the reactions proceeded faster in water than in THF, and in the absence of base. The isomerisations of monosubstituted alcohols take place rapidly (10–60 min, turn‐over frequency=750–3000 h^?1) and, in some cases, at 35 °C in 60 min. The nature of the aqueous species formed in water by this complex has been analysed by ESI‐MS. To analyse how an aqueous medium can influence the mechanism of the bifunctional catalytic process, DFT calculations (B3LYP) including one or two explicit water molecules and using the polarisable continuum model have been carried out and provide a valuable insight into the role of water on the activity of the bifunctional catalyst. Several mechanisms have been considered and imply the formation of aqua complexes and their deprotonated species generated from [Ru(η³:η³‐C₁₀H₁₆)Cl₂(pyrazole)]. Different competitive pathways based on outer‐sphere mechanisms, which imply hydrogen‐transfer processes, have been analysed. The overall isomerisation implies two hydrogen‐transfer steps from the substrate to the catalyst and subsequent transfer back to the substrate. In addition to the conventional Noyori outer‐sphere mechanism, which involves the pyrazolide ligand, a new mechanism with a hydroxopyrazole complex as the active species can be at work in water. The possibility of formation of an enol, which isomerises easily to the keto form in water, also contributes to the efficiency in water.     

Syntheses and Structures of Homo‐ and Heterobimetallic Complexes Containing a (Cyclopentadienone)rhodium(I) Fragment

The reaction of [RhCl(η⁴‐Ph₂R₂C₄CO)]₂ (R=Ph, 2‐naphthyl) with the dimeric complexes [RuCl₂(p‐cymene)]₂ p‐cymene=1‐methyl‐4‐(1‐methylethyl)benzene, [RuCl₂(1,3,5‐Et₃C₆H₃)]₂, [MCl₂(Cp*)]₂ (M=Rh, Ir; Cp*=1,2,3,4,5‐pentamethylcyclopenta‐2,4‐dien‐1‐yl), [RuCl₂(CO)₃]₂, [RuCl₂(dcypb)(CO)]₂ (dcypb=butane‐1,4‐diylbis[dicyclohexylphosphine]), [(dppb)ClRu(μ‐Cl)₂(μ‐OH₂)RuCl(dppb)] (dppb=butane‐1,4‐diylbis[diphenylphosphine]), and [(dcypb)(N₂)Ru(μ‐Cl)₃RuCl(dcypb)] was investigated. In all cases, mixed, chloro‐bridged complexes were formed in quantitative yield (see 5 – 8, 9 – 16, 18, 19, 21 , and 22 ). The six new complexes 5, 8, 9, 13, 15 , and 22 were characterized by single‐crystal X‐ray analysis (Figs. 1–3).     

π‐Ruthenium Complexes of Hexaphyrins(1.1.1.1.1.1): A Triple‐Decker Complex Bearing Two Ruthenoarene Units

Ruthenium(II) π‐coordination onto [28]hexaphyrins(1.1.1.1.1.1) has been accomplished. Reactions of bis‐Au^III and mono‐Au^III complexes of hexakis(pentafluorophenyl) [28]hexaphyrin with [RuCl₂(p‐cymene)]₂ in the presence of NaOAc gave the corresponding π‐ruthenium complexes, in which the [(p‐cymene)Ru]^II fragment sat on the deprotonated side pyrrole. A similar reaction of the bis‐Pd^II [26]hexaphyrin complex afforded a triple‐decker complex, in which the two [(p‐cymene)Ru]^II fragments sat on both sides of the center of the [26]hexaphyrin framework.     

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.     

Ruthenium(II) complexes derived from 2‐phenylthiazoline‐4‐carboxylic acid: structure and catalytic activity for transfer hydrogenation reaction

Piano‐stool ([(p‐cymene)Ru(thz)Cl], 2 ) and six‐coordinated ([Ru(thz)₂(PPh₃)₂], 3 ) ruthenium complexes derived from 2‐phenylthiazoline‐4‐carboxylic acid (Hthz, 1 ) were synthesized for the first time, and fully characterized using conventional methods. Also, the molecular structure of complex 3 was determined using X‐ray analysis. These complexes were evaluated as catalysts for transfer hydrogenation of carbonyl compounds in the presence of isopropyl alcohol and KO^tBu. Complex 2 was found to be more active than 3 in transfer hydrogenation. Copyright © 2016 John Wiley & Sons, Ltd.     

A ruthenium(II) complex with p‐cymene and (S)‐2‐(anilinomethyl)pyrrolidine

The title compound, [(S)‐2‐(anilino­methyl)­pyrrolidine‐N,N′]‐chloro(η⁶‐para‐cymene)­ruthenium(II) chloride, [RuCl‐(C₁₀H₁₄)(C₁₁H₁₆N₂)]Cl, has been synthesized by the reaction of [RuCl₂(p‐cymene)]₂ (p‐cymene is para‐iso­propyl­toluene) with (S)‐2‐(anilinomethyl)­pyrrolidine in triethyl­amine/2‐propanol. The Ru atom is in a pseudo‐tetrahedral environment coordinated by a chloride ligand, the aromatic hydro­carbon is linked in a η⁶ manner and the amine is linked via its two N atoms. The chloride anion is involved in hydrogen bonding with the di­amine moieties through N—H?Cl interactions, with N?Cl distances of 3.273 (4) and 3.352 (4) Å.