Diffusion Nuclear Magnetic Resonance Measurements on Cationic Gold (I) Complexes in Catalytic Conditions: Counterion and Solvent Effects.

The amount of free ions, ion pairs, and higher aggregate of the possible species present in a solution during the gold(I)-catalyzed alkoxylation of unsaturated hydrocarbon, i.e., ISIP (inner sphere ion pair) [(NHC)AuX] and OSIP (outer sphere ion pairs) [(NHC)Au(TME)X] [NHC 1,3-bis(2,6-di-isopropylphenyl)-imidazol-2-ylidene; TME = tetramethylethylene (2,3-bis methyl-butene); X = Cl, BF, OTf; and OTs BArF (ArF = 3,5-(CF)CH)], has been determined.

Cyclometalated and NNN Terpyridine Ruthenium Photocatalysts and Their Cytotoxic Activity.

The cyclometalated terpyridine complexes [Ru(η-OAc)(NC-tpy)(PP)] (PP = dppb , (,)-Skewphos , (,)-Skewphos ) are easily obtained from the acetate derivatives [Ru(η-OAc)(PP)] (PP = dppb, (,)-Skewphos , (,)-Skewphos ) and tpy in methanol by elimination of AcOH. The precursors , are prepared from [Ru(η-OAc)(PPh)] and Skewphos in cyclohexane. Conversely, the NNN complexes [Ru(η-OAc)(NNN-tpy)(PP)]OAc (PP = (,)-Skewphos , (,)-Skewphos ) are synthesized in a one pot reaction from [Ru(η-OAc)(PPh)], PP and tpy in methanol.

Enhanced Heterogeneous Fenton Degradation of Organic Dyes by Bimetallic Zirconia-Based Catalysts.

The qualitative impact of pollutants on water quality is mainly related to their nature and their concentration, but in any case, they determine a strong impact on the involved ecosystems. In particular, refractory organic compounds represent a critical challenge, and several degradation processes have been studied and developed for their removal. Among them, heterogeneous Fenton treatment is a promising technology for wastewater and liquid waste remediation.

-Alkylation of aromatic amines with alcohols by using a commercially available Ru complex under mild conditions.

An -alkylation procedure has been developed under very mild conditions using a known commercially available Ru-based catalyst. As a result, a wide range of aromatic primary amines has been selectively alkylated with several primary alcohols, yielding the corresponding secondary amines in high yields. The methodology also enables the methylation of anilines in refluxing methanol and the preparation of a set of heterocycles in a straightforward way.

Experimental and Theoretical Investigation of Ion Pairing in Gold(III) Catalysts.

The ion pairing structure of the possible species present in solution during the gold(III)-catalyzed hydration of alkynes: [(ppy)Au(NHC)Y]X and [(ppy)Au(NHC)X]X [ppy = 2-phenylpyridine, NHC = NHC = 1,3-bis(2,6-di-isopropylphenyl)-imidazol-2-ylidene; NHC = NHC = 1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene X = Cl, BF, OTf; Y = HO and 3-hexyne] are determined. The nuclear overhauser effect nuclear magnetic resonance (NMR) experimental measurements integrated with a theoretical description of the system (full optimization of different ion pairs and calculation of the Coulomb potential surface) indicate that the preferential position of the counterion is tunable through the choice of the ancillary ligands (NHC, NHC, ppy, and Y) in [(ppy)Au(NHC)(3-hexyne)]X activated complexes that undergo nucleophilic attack. The counterion can approach near NHC, pyridine ring of ppy, and gold atom.

Terpyridine Diphosphine Ruthenium Complexes as Efficient Photocatalysts for the Transfer Hydrogenation of Carbonyl Compounds.

The cationic achiral and chiral terpyridine diphosphine ruthenium complexes [RuCl(PP)(tpy)]Cl (PP=dppp (1), (R,R)-Skewphos (2) and (S,S)-Skewphos (3)) are easily obtained in 85-88 % yield through a one-pot synthesis from [RuCl (PPh ) ], the diphosphine and 2,2':6',2''-terpyridine (tpy) in 1-butanol. Treatment of 1-3 with NaPF in methanol at RT affords quantitatively the corresponding derivatives [RuCl(PP)(tpy)]PF (PP=dppp (1 a), (R,R)-Skewphos (2 a) and (S,S)-Skewphos (3 a)). Reaction of [RuCl (PPh ) ] with (S,R)-Josiphos or (R)-BINAP in toluene, followed by treatment with tpy in 1-butanol and finally with NaPF in MeOH gives [RuCl(PP)(tpy)]PF (PP=(S,R)-Josiphos (4 a), (R)-BINAP (5 a)) isolated in 78 % and 86 % yield, respectively.

Enantioselective Cytotoxicity of Chiral Diphosphine Ruthenium(II) Complexes Against Cancer Cells.

The chiral cationic complex [Ru(η -OAc)(CO)((R,R)-Skewphos)(phen)]OAc (2 ), isolated from reaction of [Ru(η -OAc)(η -OAc)(R,R)-Skewphos)(CO)] (1 ) with phen, reacts with NaOPiv and KSAc affording [RuX(CO)((R,R)-Skewphos)(phen)]Y (X=Y=OPiv 3 ; X=SAc, Y=OAc 4 ). The corresponding enantiomers 2 -4 have been obtained from 1 containing (S,S)-Skewphos. Reaction of 2 and 2 with (S)-cysteine and NaPF at pH=9 gives the diastereoisomers [Ru((S)-Cys)(CO)(PP)(phen)]PF (PP=(R,R)-Skewphos 2 -Cys; (S,S)-Skewphos 2 -Cys).

Preparation of Neutral [Ru(OCR)P(NN)], Cationic [Ru(OCR)P(NN)](OCR) and Pincer [Ru(OCR)(CNN)P] (P = PPh, P = diphosphine) Carboxylate Complexes and their Application in the Catalytic Carbonyl Compounds Reduction.

The diacetate complexes -[Ru(κ-OAc)(PPh)(NN)] (NN = ethylenediamine (en) (), 2-(aminomethyl)pyridine (ampy) (), 2-(aminomethyl)pyrimidine (ampyrim) ()) have been isolated in 76-88% yield by reaction of [Ru(κ-OAc)(PPh)] with the corresponding nitrogen ligands. The ampy-type derivatives and undergo isomerization to the thermodynamically most stable cationic complexes [Ru(κ-OAc)(PPh)(NN)]OAc ( and ) and -[Ru(κ-OAc)(PPh)(NN)] ( and ) in methanol at RT. The -[Ru(κ-OAc)(P)] (P = dppm (), dppe ()) compounds have been synthesized from [Ru(κ-OAc)(PPh)] by reaction with the suitable diphosphine in toluene at 95 °C.

Cationic carboxylate and thioacetate ruthenium(ii) complexes: synthesis and cytotoxic activity against anaplastic thyroid cancer cells.

The cationic acetate ruthenium complex [Ru(η1-OAc)(CO)(dppb)(phen)]OAc (1) is easily prepared in 83% yield from [Ru(η1-OAc)(η2-OAc)(CO)(dppb)] (dppb = 1,4-bis(diphenylphosphino)butane) and 1,10-phenanthroline (phen) in MeOH. The derivative 1 undergoes easy substitution of the coordinated acetate by reaction with NaOPiv, KSAc, and KSCN in MeOH, affording the corresponding complexes [RuX(CO)(dppb)(phen)]X (X = OPiv, 2; SAc, 3; and NCS, 4), whereas its reaction with NaCl and NH4PF6 affords [RuCl(CO)(dppb)(phen)]PF6 (5). Carboxylate complexes 1 and 2 show high solubility in water, enabling easy exchange of the coordinated carboxylate by water and other ligands (CH3CN, glutathione).

CNN pincer ruthenium complexes for efficient transfer hydrogenation of biomass-derived carbonyl compounds.

The ligand HCNNOMe (6-(4-methoxyphenyl)-2-aminomethylpyridine) is easily prepared from the commercially available 6-(4-methoxyphenyl)pyridine-2-carbaldehyde by the reaction of hydroxylamine and hydrogenation (H2, 1 atm) with Pd/C. The pincer complexes cis-[RuCl(CNNOMe)(PPh3)2] (1) and [RuCl(CNNOMe)(PP)] (PP = dppb, 2; and dppf, 3) are synthesized from [RuCl2(PPh3)3], HCNNOMe and PP (for 2 and 3) in 2-propanol with NEt3 at reflux and are isolated in 85-93% yield. Carbonylation of 1 (CO, 1 atm) gives [RuCl(CNNOMe)(CO)(PPh3)] (4) (79% yield) which cleanly reacts with Na[BArf4] and PCy3, affording the cationic trans-[Ru(CNNOMe)(CO)(PCy3)(PPh3)][BArf4] (5) (92% yield).

Preparation of monocarbonyl ruthenium complexes bearing bidentate nitrogen and phosphine ligands and their catalytic activity in carbonyl compound reduction.

Monocarbonyl complexes [RuCl(CO)(PR)(NN)] (R = Cy, NN = en 1, ampy 2; R = iPr; NN = en 3) have been prepared in a one pot reaction from [RuCl(CO)(dmf)(PPh)], PR and the NN ligand in CHCl. Treatment of [Ru(OAc)(CO)(PPh)] with NN ligands in methanol gives the cationic derivatives [Ru(OAc)(CO)(PPh)(NN)]OAc (NN = en 4, ampy 5) in which one acetate acts as a bidentate ligand, whereas the other is not coordinated. Diphosphine complexes [RuCl(CO)(PP)(PPh)] (PP = dppb 6, dppf 7, (R)-BINAP 8, (R,S)-Josiphos 9 and (R,R)-Skewphos 10) have been obtained starting from [RuCl(CO)(dmf)(PPh)] and the PP ligand in CHCl or toluene at reflux.

Mitochondrial F-ATP Synthase and Its Transition into an Energy-Dissipating Molecular Machine.

The mitochondrial F-ATP synthase is the principal energy-conserving nanomotor of cells that harnesses the proton motive force generated by the respiratory chain to make ATP from ADP and phosphate in a process known as oxidative phosphorylation. In the energy-converting membranes, F-ATP synthase is a multisubunit complex organized into a membrane-extrinsic F sector and a membrane-intrinsic F domain, linked by central and peripheral stalks. Due to its essential role in the cellular metabolism, malfunction of F-ATP synthase has been associated with a variety of pathological conditions, and the enzyme is now considered as a promising drug target for multiple disease conditions and for the regulation of energy metabolism.

Ru(OCCF)(PPh) and ruthenium phosphine complexes bearing fluoroacetate ligands: synthesis, characterization and catalytic activity.

The dinuclear ruthenium(ii) phosphine complexes Ru2Cl(O2CCHxF3-x)3(PPh3)4(μ-H2O) (x = 0, 1, 2), containing fluoroacetate ligands, were prepared from RuCl2(PPh3)3 and NaO2CCHxF3-x in tBuOH. The X-ray characterization of these complexes reveals a bridging water molecule, stabilized by hydrogen bonds with the fluoroacetate ligands. The isolation of the complex Ru(O2CCF3)2(PPh3)2 is described, starting from RuCl2(PPh3)3 or Ru2Cl(O2CCF3)3(PPh3)4(μ-H2O) and TlO2CCF3, correcting the reported preparation in which Ru2Cl(O2CCF3)3(PPh3)4(μ-H2O) was obtained.

Cationic abnormal N-heterocyclic carbene ruthenium complexes as suitable precursors for the synthesis of heterobimetallic compounds.

The cationic abnormal N-heterocyclic carbene complex [Ru(OAc)(dppe)(PC)]Br (2b) (PC = bidentate phosphine-carbene ligand) has been obtained by treatment of the neutral derivative RuBr(OAc)(PPh3)(PC) (2a) with dppe in THF. Reaction of 2b with Ag2O afforded the heterobimetallic complex Ru(OAc)(dppe)(PC)AgBr (2c) which can be easily transmetallated with [Ir(cod)Cl]2 giving Ru(OAc)(dppe)(PC)IrCl(cod) (2d). Similarly, [{Ru(OAc)(PC)(PC')}2Ag][AgBr2] (1b) reacts with [Ir(cod)Cl]2 with formation of Ru(OAc)(PC)(PC')IrCl(cod) (1e).

Mild N-Alkylation of Amines with Alcohols Catalyzed by the Acetate Ru(OAc) (CO)(DiPPF) Complex.

The acetate complex Ru(OAc) (DiPPF) (2) obtained from Ru(OAc) (PPh )  (1) and 1,1'-bis(diisopropylphosphino)ferrocene (DiPPF) reacts cleanly with formaldehyde affording Ru(OAc) (CO)(DiPPF) (3) in high yield. The monocarbonyl complex 3 (0.4-2 mol %) efficiently catalyzes the N-alkylation of primary and secondary alkyl and aromatic amines using primary alcohols ROH (R=Et, nPr, nBu, PhCH ) under mild reaction conditions (30-100 °C) with an alcohol/amine molar ratio of 10-100.

Ru-Ag and Ru-Au dicarbene complexes from an abnormal carbene ruthenium system.

Reaction of [Ru(OAc)2(PPh3)2] with a P-functionalized imidazolium bromide easily affords a cationic abnormal carbene Ru system. Metalation with Ag2O yields a Ru-Ag complex containing an anionic dicarbene ligand, while subsequent transmetalation with Au(tht)Cl leads to the corresponding Ru-Au system. The bimetallic complexes were characterized by single crystal X-ray diffraction and are the first examples of complexes bearing anionic dicarbene ligands connecting two different d-block elements.

Recent advances in osmium-catalyzed hydrogenation and dehydrogenation reactions.

CONSPECTUS: A current issue in metal-catalyzed reactions is the search for highly efficient transition-metal complexes affording high productivity and selectivity in a variety of processes. Moreover, there is also a great interest in multitasking catalysts that are able to efficiently promote different organic transformations by careful switching of the reaction parameters, such as temperature, solvent, and cocatalyst. In this context, osmium complexes have shown the ability to catalyze efficiently different types of reactions involving hydrogen, proving at the same time high thermal stability and simple synthesis.

CNN pincer ruthenium catalysts for hydrogenation and transfer hydrogenation of ketones: experimental and computational studies.

Reaction of [RuCl(CNN)(dppb)] (1-Cl) (HCNN=2-aminomethyl-6-(4-methylphenyl)pyridine; dppb=Ph2 P(CH2 )4 PPh2 ) with NaOCH2 CF3 leads to the amine-alkoxide [Ru(CNN)(OCH2 CF3 )(dppb)] (1-OCH2 CF3 ), whose neutron diffraction study reveals a short RuO⋅⋅⋅HN bond length. Treatment of 1-Cl with NaOEt and EtOH affords the alkoxide [Ru(CNN)(OEt)(dppb)]⋅(EtOH)n (1-OEt⋅n EtOH), which equilibrates with the hydride [RuH(CNN)(dppb)] (1-H) and acetaldehyde. Compound 1-OEt⋅n EtOH reacts reversibly with H2 leading to 1-H and EtOH through dihydrogen splitting.

Pincer Ru and Os complexes as efficient catalysts for racemization and deuteration of alcohols.

The pincer complexes [MX(CNN)(PP)] (M = Ru, Os; X = Cl, OTf; HCNN = 1-(6-arylpyridin-2-yl)methanamine; PP = diphosphine) have proven to efficiently catalyze both racemization and deuteration of alcohols in the presence of a base. Chiral alcohols have been racemized at 30-50 °C using 1 mol% of Ru or Os pincer complexes and 5 mol% of KOtBu in 2-propanol. Primary and secondary alcohols are efficiently deuterated at the α position, with respect to the OH group, using 2-propanol-d(8) as solvent with Ru or Os pincer complexes and KOtBu at 30-50 °C.

Pincer and diamine Ru and Os diphosphane complexes as efficient catalysts for the dehydrogenation of alcohols to ketones.

The ruthenium and osmium complexes [MCl(2)(diphosphane)(L)] (M=Ru, Os; L=bidentate amino ligand) and [MCl(CNN)(dppb)] (CNN=pincer ligand; dppb=1,4-bis-(diphenylphosphino)butane), containing the N−H moiety, have been found to catalyze the acceptorless dehydrogenation of alcohols in tBuOH and in the presence of KOtBu. The compounds trans-[MCl(2)(dppf)(en)] (M=Ru 7, Os 13; dppf=1,1'-bisdiphenylphosphino)ferrocene; en=ethylenediamine) display very high activity and different substrates, including cyclic and linear alcohols, are efficiently oxidized to ketones by using 0.8-0.

Chiral and nonchiral [OsX2(diphosphane)(diamine)] (X: Cl, OCH2CF3) complexes for fast hydrogenation of carbonyl compounds.

The osmium complexes trans-[OsCl(2)(dppf)(diamine)] (dppf: 1,1'-bis(diphenylphosphino)ferrocene; diamine: ethylenediamine in 3, propylenediamine in 4) were prepared by the reaction of [OsCl(2)(PPh(3))(3)] (1) with the ferrocenyl diphosphane, dppf and the corresponding diamine in dichloromethane. The reaction of derivative 3 with NaOCH(2)CF(3) in toluene afforded the alkoxide cis-[Os(OCH(2)CF(3))(2)(dppf)(ethylenediamine)] (5). The novel precursor [Os(2)Cl(4)(P(m-tolyl)(3))(5)] (2) allows the synthesis of the chiral complexes trans-[OsCl(2)(diphosphane)(1,2-diamine)] (6-9; diphosphane: (R)-[6,6'-dimethoxy(1,1'-biphenyl)-2,2'-diyl]bis[1,1-bis(3,5-dimethylphenyl)phosphane] (xylMeObiphep) or (R)-(1,1'-binaphthalene)-2,2'-diylbis[1,1-bis(3,5-dimethylphenyl)phosphane] (xylbinap); diamine=(R,R)-1,2-diphenylethylenediamine (dpen) or (R,R)-1,2-diaminocyclohexane (dach)), obtained by the treatment of 2 with the diphosphane and the 1,2-diamine in toluene at reflux temperature.

Efficient chemoenzymatic synthesis of chiral pincer ligands.

Chiral, nonracemic pincer ligands based on the 6-phenyl-2-aminomethylpyridine and 2-aminomethylbenzo[h]quinoline scaffolds were obtained by a chemoenzymatic approach starting from 2-pyridyl and 2-benzoquinolyl ethanone. In the enantiodifferentiating step, secondary alcohols of opposite absolute configuration were obtained by a baker's yeast reduction of the ketones and by lipase-mediated dynamic kinetic resolution of the racemic alcohols. Their transformation into homochiral 1-methyl-1-heteroarylethanamines occurred without loss of optical purity, giving access to pincer ligands used in enantioselective catalysis.

Highly productive CNN pincer ruthenium catalysts for the asymmetric reduction of alkyl aryl ketones.

Chiral pincer ruthenium complexes of formula [RuCl(CNN)(Josiphos)] (2-7; Josiphos = 1-[1-(dicyclohexylphosphano)ethyl]-2-(diarylphosphano)ferrocene) have been prepared by treating [RuCl(2)(PPh(3))(3)] with (S,R)-Josiphos diphosphanes and 1-substituted-1-(6-arylpyridin-2-yl)methanamines (HCNN; substituent = H (1 a), Me (1 b), and tBu (1 c)) with NEt(3). By using 1 b and 1 c as a racemic mixture, complexes 4-7 were obtained through a diastereoselective synthesis promoted by acetic acid. These pincer complexes, which display correctly matched chiral PP and CNN ligands, are remarkably active catalysts for the asymmetric reduction of alkyl aryl ketones in basic alcohol media by both transfer hydrogenation (TH) and hydrogenation (HY), achieving enantioselectivities of up to 99 %.

New benzo[h]quinoline-based ligands and their pincer Ru and Os complexes for efficient catalytic transfer hydrogenation of carbonyl compounds.

New benzo[h]quinoline ligands (HCN'N) containing a CHRNH2 (R=H (a), Me (b), tBu (c)) function in the 2-position were prepared starting from benzo[h]quinoline N-oxide (in the case of ligand a) and 2-chlorobenzo[h]quinoline (for ligands b and c). These compounds were used to prepare ruthenium and osmium complexes, which are excellent catalysts for the transfer hydrogenation (TH) of ketones. The reaction of a with [RuCl2(PPh3)3] in 2-propanol at reflux afforded the terdentate CN'N complex [RuCl(CN'N)(PPh3)2] (1), whereas the complexes [RuCl(CN'N)(dppb)] (2-4; dppb=Ph2P(CH2)4PPh2) were obtained from [RuCl2(PPh3)(dppb)] with a-c, respectively.