Complexes 2a Research Articles

P-Ru-Complexes with a Chelate-Bridge-Switch: A Comparison of 2-Picolyl and 2-Pyridyloxy Moieties as Bridging Ligands.

Starting from [Ru(pyO)2(nbd)] 1 and a N,P,N-tridentate ligand (2a: PhP(pic)2, 2b: PhP(pyO)2) (nbd = 2,5-norbornadiene, pic = 2-picolyl = 2-pyridylmethyl, pyO = 2-pyridyloxy = pyridine-2-olate), the compounds [PhP(μ-pic)2(μ-pyO)Ru(κ2-pyO)] (3a) and [PhP(μ-pyO)3Ru(κ2-pyO)] (3b), respectively, were prepared. Reaction of compounds 3 with CO and CNtBu afforded the opening of the Ru(κ2-pyO) chelate motif with the formation of compounds [PhP(μ-pic)2(μ-pyO)Ru(κ-O-pyO)(CO)] (4a), [PhP(μ-pic)2(μ-pyO)2Ru(CNtBu)] (5a), [PhP(μ-pyO)4Ru(CO)] (4b) and [PhP(μ-pyO)4Ru(CNtBu)] (5b). In dichloromethane solution, 4a underwent a reaction with the solvent, i.e., substitution of the dangling pyO ligand by chloride with the formation of [PhP(μ-pic)2(μ-pyO)Ru(Cl)(CO)] (6a). The new complexes 3a, 4a, 5a, 5b and 6a were characterized by single-crystal X-ray diffraction analyses and multi-nuclear (1H, 13C, 31P) NMR spectroscopy. The different coordination behaviors of related pairs of molecules (i.e., pairs of 3, 4 and 5), which depend on the nature of the P–Ru-bridging ligand moieties (μ-pic vs. μ-pyO), were also studied via computational analyses using QTAIM (quantum theory of atoms in molecules) and NBO (natural bond orbital) approaches, as well as the NCI (non-covalent interactions descriptor) for weak intramolecular interactions.

Synthesis of novel luminescent cyclometallated platinum (IV) complexes with a quinoline Schiff bases ligand and their photophysical properties

The synthesis, characterization, electro and photophysical properties of eight cyclometallated platinum (IV) complexes 6a–6d and 7a–7d derived from quinoline Schiff base ligands are reported. Spectral studies revealed that nonparticipation of nitrogen atom and participation of carbon atom of the quinoline ring in the bond formation through [NN′C] mode of coordination for complex 6, whereas [N S O] mode of coordination with octahedral geometry for complex 7. The absorption and emission spectra studied in acetonitrile medium at room temperature showed that the ligand charge transitions within the quinoline Schiff base ligands with Metal Ligand Charge Transfer (MLCT) character. The broad band appeared in the range of 460–502 nm is attributed to the higher emission intensities of cyclometallated platinum (IV) compounds. The HOMO, LUMO and energy gap of the synthesized complexes was found to be − 2.60 eV, −4.75 eV and 2.15 eV through Density Functional Theory (DFT).

Theoretical Approach for the Luminescent Properties of Ir(III) Complexes to Produce Red-Green-Blue LEC Devices.

With an appropriate mixture of cyclometalating and ancillary ligands, based on simple structures (commercial or easily synthesized), it has been possible to design a family of eight new Ir(III) complexes (1A, 1B, 2B, 2C, 3B, 3C, 3D and 3E) useful as luminescent materials in LEC devices. These complexes involved the use of phenylpyridines or fluorophenylpyridines as cyclometalating ligands and bipyridine or phenanthroline-type structures as ancillary ligands. The emitting properties have been evaluated from a theoretical approach through Density Functional Theory and Time-Dependent Density Functional Theory calculations, determining geometric parameters, frontier orbital energies, absorption and emission energies, injection and transport parameters of holes and electrons, and parameters associated with the radiative and non-radiative decays. With these complexes it was possible to obtain a wide range of emission colours, from deep red to blue (701–440 nm). Considering all the calculated parameters between all the complexes, it was identified that 1B was the best red, 2B was the best green, and 3D was the best blue emitter. Thus, with the mixture of these complexes, a dual host–guest system with 3D-1B and an RGB (red–green–blue) system with 3D-2B-1B are proposed, to produce white LECs.

Crystal structure, optical properties, spectroscopic characterization and density functional theory studies of a new rhodium(i)-imidazolidin-2-ylidene complexes: Synthesis, characterization and cytotoxic properties

Rhodium(I) complexes bearing imidazolidin-2-ylidene ligands have been widely used in catalytic chemistry, but there are very few reports of the biological properties of these type complexes. A series of [RhCl(COD)(NHC)] complexes were synthesized. The structures of all compounds were characterized by 1H NMR, 13C NMR, IR and elemental analysis techniques, which supported the proposed structures. The single-crystal structures of complexes 1a and 1c have been determined. Single-crystal X-ray diffraction analysis indicates that complexes 1a and 1c crystallize in the centrosymmetric space groups P n m a and I 1 2/a 1 of the orthorhombic and monoclinic systems respectively. The ground state geometry of these complexes was optimized using density functional theory (DFT) at mixed double ζ basis set, 6-31G(d) for H, C, N, O and Cl and LANL2DZ for Rh. The presence of the different functional groups and the nature of their vibrations were identified by the experimental and theoretical infrared spectra. The optical properties of the studied complex were determined experimentally using UV–visible and photoluminescence techniques in solid-state and theoretically using the TD-DFT method. Hirshfeld surface analysis employing 3D molecular surface contours and 2D fingerprint plots has been used to analyze intermolecular interactions present in the solid-state. The cytotoxic properties of the rhodium(I)–NHC complexes have been assessed in various human cancer lines, including cisplatin-sensitive and resistant cells. IC50 values of these four complexes were determined by the MTS-based assay on three human cancer cell lines; brain (SH-SY5Y), colon (HTC116), and liver (Hep 3B). Substances 1a-d showed 100% anticarcinogenic effect in cancer cell lines at 50 and 100 µM.

Ruthenium(II) complexes bearing benzimidazole-based N-heterocyclic carbene (NHC) ligands as potential antimicrobial, antioxidant, enzyme inhibition, and antiproliferative agents

In this work, new substituted benzimidazolium salts 2a–d having different groups on the side chain have been synthesized and reacted with Ag2O to produce Ag(I) N-heterocyclic carbene (NHC) complexes 3a–d. Ag(I)-NHC complexes were used as a carben transfer agents to synthesize ruthenium(II)-NHC complexes 4a–d. The structures of all compounds were characterized by 1H NMR, 13C NMR and FT-IR spectroscopies and elemental analysis. The IC50 values of these complexes were determined by MTT assay against MCF7, MDA-MB-231 and HF cancer cell lines. The lowest MIC values were obtained for two complexes, 4b and 4d. The Ru(II)-NHC complexes generally triggered stronger bacterial growth inhibition than the metal-free benzimidazolium cations. Enzymatic inhibition investigation against acetylcholinesterase (AChE) and tyrosinase (TyrE) showed that 4b and 4d are the most potent inhibitors against AchE with an IC50 of 2.52 and 5.06 µg mL−1, respectively, and against TyrE with an IC50 of 19.88 and 24.95 µg mL−1, respectively. Antioxidant activity of the synthesized NHC ligands 2a–2d and their respective Ru(II)-NHC complexes 4a–4d was assessed by three different techniques: the 2.2-diphenyl-1-picrylhydrazyl (DPPH), the 2.2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radicals scavenging and the β-carotene linoleic acid bleaching assay, showing that 4d has recorded an important antioxidant activity.

Self-assembly synthesis of diorganotin complexes based on arylformylhydrazone possessing ONO donor set: anticancer activity and mechanism.

Fourteen new organotin(IV) complexes were successfully synthesized and characterized by elemental analyses, Fourier transform infrared spectroscopy (FT-IR), multinuclear (1H, 13C, and 119Sn) NMR spectroscopy, high-resolution mass spectrometry (HRMS), and X-ray single-crystal techniques. Crystallographic data showed that the complexes 1b, 2b, 3b, and 5b were macrocyclic compounds, 4b exhibited a one-dimensional spiral chain structure with distorted trigonal bipyramidal geometry, other complexes were centrosymmetric dimers, and there was an Sn2O2 four-membered ring in the middle of the molecule. In-vitro anticancer activity against the three human tumor cell lines NCI-H460, MCF-7, and HepG2 was studied, and the dibutyltin complex 5a is a more potent antitumor agent than other complexes and cisplatin. Cell apoptosis study of 5a with the highest activity on HepG2 cancer cell lines was done by flow cytometry; it was shown that the antitumor activity of 5a was related to apoptosis, and it inhibited proliferation by blocking cells in the G2/M phase. The single-cell gel electrophoresis assay results show that 5a induces DNA damage. 5a interacts with ct-DNA by intercalating the mode of interaction. UV-visible absorption spectrometry, fluorescence competitive, viscosity measurements, and gel electrophoresis results also support the intercalative mode of interaction for 5a with DNA.

Scalable Rhodaelectro-Catalyzed Expedient Access to Seven-Membered Azepino[3,2,1- hi ]indoles via [5 + 2] C–H/N–H Annulation

Scalable Rhodaelectro-Catalyzed Expedient Access to Seven-Membered Azepino[3,2,1- <i>hi</i> ]indoles via [5 + 2] C–H/N–H Annulation

Silver(I) complexes with phenolic Schiff bases: Synthesis, antibacterial evaluation and interaction with biomolecules.

Novel Ag(I) complexes (2a–2c) with phenolic Schiff bases were synthesized using 4,6-di-tert-butyl-3-(((5-mercapto-1,3,4-thiadiazol-2-yl)imino)methyl)benzene-1,2-diol (1a), 4,6-di-tert-butyl-3-(((4-mercaptophenyl)imino)methyl)benzene-1,2-diol (1b), and 4,6-di-tert-butyl-3-(((3-mercaptophenyl)imino)methyl)benzene-1,2-diol (1c). They were examined by elemental analysis, FT-IR, UV-Vis, 1H-NMR spectroscopy, XRD, cyclic voltammetry, conductivity measurements, and biological methods. The complexes are characterized by distorted geometry of the coordination cores AgN2S2 (2c), AgNS (2b) and AgS2 (2a). These stable complexes were not typified by the intramolecular redox reaction in organic solvents resulting in the formation of silver nanoparticles (AgNPs). Antibacterial activity of 1a–1c and 2a–2c was evaluated in comparison with AgNPs and commonly used antibiotics. All the complexes were more active than the ligands against the bacteria tested (14), but they were less active than AgNPs and commonly used antibiotics. Both 1a–1c and their complexes 2a–2c exhibited the capability for the bovine heart Fe(III)-Cyt c reduction. The ligands 1b and 1c were characterized by the highest reduction rate among the compounds under study, and they showed a higher reducing ability (determined by cyclic voltammetry) as compared with that of their Ag(I) complexes 2b and 2c.

Stepwise Access of Emissive Ir(III) Complexes Bearing a Multi-Dentate Heteroaromatic Chelate: Fundamentals and Applications.

Three multi-dentate coordinated chelates LnH2 (n = 1, 2, and 3), comprising a linked 1-(pyridin-2-yl)ethylbenzene and one pyrazolyl pyridine unit and showing either tridentate or tetradentate coordination modes, are successfully designed and synthesized. Dinuclear Ir(III) complexes [Ir(κ4-Ln)(μ-Cl)]2 bearing tetradentate coordinated κ4-Ln chelate (2a, n = 1; 2b, n = 2; 2c, n = 3) were next obtained en route from the respective intermediate [Ir(κ3-LnH)Cl(μ-Cl)]2 bearing the tridentate coordinated κ3-LnH chelate (1a, n = 1; 1b, n = 2; 1c, n = 3). Next, mononuclear Ir(III) complexes Ir(κ4-Ln)(thd) (3a, n = 1; 3b, n = 2; 3c, n = 3) with the tetradentate chelate were obtained upon treatment of 2 with 2,2,6,6-tetramethyl-3,5-heptanedione (thd)H in the presence of K2CO3. Concurrently, methylation of 2c in the presence of MeI and nBu4NCl afforded tridentate Ir(κ3-L3HMe)Cl3 (4) and, next, can be converted to tetradentate Ir(κ4-L3Me)Cl2 (5) by further cyclometalation and HCl elimination in refluxing diethylene glycol monoethyl ether solution. The Ir(III) complexes 3a, 4, and 5 were unambiguously identified using spectroscopic methods, together with single-crystal X-ray structural analyses on Ir(III) derivatives 3a, 4, and 5. Their photophysical and ,electrochemical properties and device fabrication properties were also investigated and compared with results from theoretical studies.

Synthesis of pyrrolidinyl-ethylene fluorenyl rare-earth metal complexes and catalysis for 2-vinylpyridine polymerization

The metathesis reaction between pyrrolidinyl-ethylene fluorenyl lithium salts with in situ prepared cationic rare-earth metal dialkyl species [Ln(CH2SiMe3)2(THF)x][BPh4] afford efficiently the corresponding constrained-geometry complexes L1Ln(CH2SiMe3)2 (L1 = FluCH2CH2NC4H8, Ln = Y (1a), Lu (1b), Sc (1c)) and L2Ln(CH2SiMe3)2 (L2 = (2,7-di-tert-butyl)FluCH2CH2NC4H8, Ln = Y (2a), Lu (2b), Sc (2c)) in good yields. All these complexes were characterized by NMR spectroscopy, and the solid-state molecular structure of yttrium complex 1a was defined with single-crystal X-ray diffraction analysis. The catalytic performance of these complexes towards 2-vinylpyridine polymerization was investigated, where these complexes alone can efficiently promote the polymerization of 2-vinylpyridine giving isotactic poly(2-vinylpyridine). Upon the activation with [Ph3C][B(C6F5)4], the yttrium and lutetium complexes also afford isotactic poly(2-vinylpyridine), while the scandium complexes produce syndiotactic poly(2-vinylpyridine).

Cyclic Palladium Formamidinate: Synthesis, Structure, Reactivity, and Application to Suzuki-Miyaura Cross-Coupling.

The deprotonation of acyclic palladium amidine chloride (1) with potassium tert-butoxide in tetrahydrofuran results in palladium bis(formamidinate) (2). 2 undergoes a nucleophilic addition reaction with acetonitrile in the presence of PdCl2 or Pd(OAc)2 (OAc = acetate) to give dinuclear cyclic six-membered (triazapentadiene)palladium complexes (4a and 4b). These compounds are also prepared from cyclic six-membered (tap)PdCl2 (5; tap = triazapentadiene) or formamidinium salts (6a-6c) with Pd(OAc)2/NaOAc in acetonitrile, whereas the direct reaction of 2 with acetonitrile or acrylonitrile resulted in palladium black or an acyclic C-N-coupled product (3). A comparison of structure 4 from 2 suggests a possible intermediate dinuclear palladium complex whose structure was identified through theoretical calculations. Further, Suzuki-Miyaura cross-coupling reactions were carried out under different solvents notably in an ethanol/water medium at room temperature.

Iron-Catalyzed H/D Exchange of Primary Silanes, Secondary Silanes, and Tertiary Siloxanes.

A synthetic study into the catalytic hydrogen/deuterium (H/D) exchange of 1° silanes, 2° silanes, and 3° siloxanes is presented, facilitated by iron-β-diketiminato complexes (1a and 1b). Near-complete H/D exchange is observed for a variety of aryl- and alkyl-containing hydrosilanes and hydrosiloxanes. The reaction tolerates alternative hydride source pinacolborane (HBpin), with quantitative H/D exchange. A synthetic and density functional theory (DFT) investigation suggests that a monomeric iron-deuteride is responsible for the H/D exchange.

CATALYSIS OF HYDRODEHALOGENATION RE­ACTION OF HALOARENES BY CARBENE PEPPSI-PALLADIUM COMPLEXES

The synthesis of a number of carbene PEPPSI-complexes of palladium with various pyridine and carbene ligands was carried out by reactions of 1,3-bis-(2,6-dibenzhydryl-4-methyl­phenyl)imidazolium chloride IPr*.HCl [compounds 7a-c IPr*PdCl2L’, L’ = pyridine (а), 3-chloropyridine (b), 4-dimethylaminopyridine (с)], 1,3-bis-(2,6-diisopropylphenyl)­imida­zo­li­um perchlorate IPr.HClO4 [compounds 8a,b IPr.PdCl2L’, L’ = 3-chloropyridine (а), о-phenanthroline (b)], 1,3-diphenyl-4-(2,6-diisopropylphenyl)-1,2,4-triazolium perchlorate L.HClO4 (complex 9 LPdCl2L’, L’ = 3-chloropyridine) and 1,3-dicetyl­imidazolium bromide L.HBr (complex 11 LPdCl2L’, L’ = pyridine) with palladium chloride in pyridines (pyridine, 3-chloropyridine), or acetonitrile in the presence of potassium carbonate. Yields of compounds – from high (56–100%) to moderate (36 %). The structure of the compounds was confirmed by 1H and 13C NMR spectroscopy. Chemical shifts of carbene atoms in the 13C NMR spectra of complexes 7a-c. 8a, b 11 are in the region 151.0-156.2 ppm, for complex 9 - at  174.4 ppm A high catalytic effect of sterically shielded complexes 7a, b, 8a, b in the hydrodehalogenation reaction of p-dichlorobenzene and hexachlorobenzene under the action of potassium tert-butoxide in isopropanol was established. 1,3-Bis-(2,6-dibenzhydryl-4-methylphenyl)-imidazol-2-ylidene complexes 7a, b (quantitative conversions with p-dichlorobenzene are achieved with 0.013 mol% of catalyst) show the highest efficiency, but the compound with 4-dimethylaminopyridine ligand 7c has significantly lower efficiency (22% conversion under these conditions). Complexes with 1,3-bis-(2,6-diisopropylphenyl)-imidazol-2-ylidene ligand 8a, b are close in efficiency to compounds 7a, b (for 7a quantitative conversion is achieved with 0.026 mol% of catalyst). Phenanthroline-containing complex 8b is less effective than complex 8a (87% conversion with 0.052 mol% of catalyst). Complex 9 is much less effective (even with 0.13 mol% of catalyst 13% conversion is achieved). Compound 11 catalyzes the reaction well only when the amount of catalyst is up to 1.3 mol% (98% conversion). Thus, compounds 7a, b, 8a are the best PEPPSI-catalysts for hydrodehalogenation of haloarenes promising for industrial decontamination of persistent orga­nic pollutants (hexachlorobenzene, DDT, di­oxins and polychlorinated biphenyls, etc.).

A versatile study of novel A3B-type unsymmetric zinc(II) phthalocyanines containing thiazolidin-4-one: Their, carbonic anhydrase I, II isoenzymes, and xanthine oxidase inhibitors evaluation

In this study, four novel phthalocyanine complexes containing zinc metal were synthesized. After preparing the starting compounds (2-(4-hydroxyphenyl)-3-phenylthiazolidin-4-one 1 and 2-(4-(2-hydroxyethoxy)phenyl)-3-phenylthiazolidin-4-one 3 by the conventional method, they were reacted with 4-nitrophthalonitrile separately using K2CO3 in DMF. Compounds 2 and 4, are well-documented compounds for obtaining phthalocyanines. Subsequently, synthesized phthalonitrile compounds 2 and 4 were reacted with Zn(II) salt at high temperature in the presence of DBU to convert them into targeted symmetrical (2a, 4a) and unsymmetrical (2b, 4b) phthalocyanines under suitable conditions. Their photochemical, photophysical, and electrochemical features were then examined. These metallophthalocyanines indicated good solubility in some organic solvents, such as DMSO, DMF, THF, DCM, and CHCl3. Furthermore, the structures of ligands (1, 2, 3, 4) were determined by 1H NMR, 13C NMR, and FT-IR spectrometry, while complexes (2a, 2b, 4a, 4b) were determined by FT-IR, UV–Vis, fluorescence, and MALDI-TOF spectrometry. Inhibitory effects of ligand and phthalocyanine compounds (1, 2, 3, 4, 2a, 2b, 4a, 4b) against human erythrocyte carbonic anhydrase I (hCA I) and II (hCA II) isoenzymes, as well as cow's milk xanthine oxidase (XO), were examined. It was found that 2a, 2b, 4a, and 4b had strong inhibition effects at micromolar levels against all three. The compounds 2b and 4b showed stronger inhibition effects for hCA I and II than 2a and 4a. In the case of XO, although the inhibition effects of these molecules (2b, 4a, 4b) were similar, 2a had the strongest inhibition effect. Since CA and XO inhibitors are the target molecules of drug development studies to be used in the treatment of many diseases, the results of this study will aid drug design studies in the development of new XO and CA inhibitors.

P–Nitrobenzyl-substituted N–heterocyclic carbene in Silver(I) and Gold(I) complexes and their antibacterial activities

The synthesis of the silver(I) N–heterocyclic carbene [Ag(NBMIM)Cl]2 (2) from the reaction of imidazolium salt {NBMIM}Cl (1a) (NBMIM = 1–methyl–3–(4–nitrobenzyl)–1H–imidazol–3–ium) and silver(I) oxide was achieved. Compound {NBMIM}PF6 (1b) was also obtained by a counteranion exchange reaction. Compound 2 was used as a transmetalation agent to form Au(I) monocarbene complex (3a) and biscarbene complex (3b), by using [AuCl(SMe2)]. All compounds were characterized in solution by infrared spectroscopy and by 1H and 13C{1H} NMR. The molecular structures of compounds {NBMIM}PF6 (1b), [Ag(NBMIM)Cl]2 (2), and [Au(NBMIM)Cl] (3a) were also determined by single crystal X–ray diffraction studies. The molecular structure of silver complex 2 showed a 1D–staircase structure with Ag⋯Ag and Ag⋯Cl intermolecular interactions. Compounds 2 and 3a were also characterized by elemental analysis, powder X–ray diffraction (PXRD), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) measurement. In preliminary in vitro antibacterial assays, compounds 2 and 3a were tested against four bacterial strains: two Gram positive (S. aureus and B. subtilis) and two Gram negative species (P. aeruginosa and E. coli) by Kirby–Bauer’s disk diffusion method. Compound 2 exhibited moderate antibacterial activity against both types of bacteria. Both silver(I) and gold(I) N–heterocyclic carbenes showed from good to high antibacterial activity against S. aureus and P. aeruginosa and moderate activity against B. subtilis and E. coli strains.

A simple synthetic entryway into (N‐heterocyclic carbene)gold‐steroidyl complexes and their anticancer activity

A straightforward synthetic route to new N‐heterocyclic carbene (NHC)‐gold‐steroidyl complexes is reported. The desired complexes were obtained using a weak base (such as K2CO3) through a concerted‐metallation‐deprotonation (CMD) reaction mechanism occurring between [Au(NHC)Cl] and ethisterone as a model steroid‐based alkyne. Most complexes displayed good cytotoxicity against a panel of cancer cell lines with IC50 values in the low micromolar range. Cellular uptake of the most active complex 2a into MCF‐7 breast cancer cells was facilitated by the coordinated ethisterone ligand.

RNA-Binding Protein MAC5A Is Required for Gibberellin-Regulated Stamen Development.

The development of floral organs is coordinated by an elaborate network of homeotic genes, and gibberellin (GA) signaling is involved in floral organ development; however, the underlying molecular mechanisms remain elusive. In the present study, we found that MOS4-ASSOCIATED COMPLEX 5A (MAC5A), which is a protein containing an RNA-binding motif, was involved in the development of sepals, petals, and stamens; either the loss or gain of MAC5A function resulted in stamen malformation and a reduced seed set. The exogenous application of GA considerably exacerbated the defects in mac5a null mutants, including fewer stamens and male sterility. MAC5A was predominantly expressed in pollen grains and stamens, and overexpression of MAC5A affected the expression of homeotic genes such as APETALA1 (AP1), AP2, and AGAMOUS (AG). MAC5A may interact with RABBIT EARS (RBE), a repressor of AG expression in Arabidopsis flowers. The petal defect in rbe null mutants was at least partly rescued in mac5a rbe double mutants. These findings suggest that MAC5A is a novel factor that is required for the normal development of stamens and depends on the GA signaling pathway.

Synthesis and characterization of novel PEPPSI type bicyclic (alkyl)(amino)carbene (BICAAC)-Pd complexes

A series of bicyclic alkylamino carbenes (BICAAC) (where N-aryl = dipp, mes, 2,6-dimethyl-4-(dimethylamino)phenyl, 5a–d) and their novel air- and moisture-resistant pyridine (pyridine, 4-dimethylaminopyridine) containing palladium Pd(II) complexes (6a–e) were synthetized and characterized. As novel examples of the PEPPSI (“pyridine enhanced precatalyst preparation stabilization and initiation”)-Pd compounds, the reported complexes have shown high activity in Mizoroki–Heck coupling reaction even at as low as 100 ppm loading (TON up to 10000). Kinetic studies revealed that reactions carried out in the presence of elemental mercury resulted decrease in activity. It indicates that the coupling reaction may have both molecular and Pd(0)-mediated catalytic paths.

Steric, Activation Method and Solvent Effects on the Structure of Paddlewheel Diruthenium Complexes

Conventional heating and solvothermal synthetic methods (with or without microwave activation) have been used to study the reaction of o-, m- and p-methoxybenzoic acid with [Ru2Cl(μ-O2CMe)4]. The tetrasubstituted series [Ru2Cl(µ-O2CC6H4-R)4], with R = o-OMe, m-OMe and p-OMe, has been prepared by the three procedures. Depending on the synthetic method and the experimental conditions, three compounds have been isolated (1a, 1b, 1c) with the o-methoxybenzoate ligand. However, with the m- and p-methoxybenzoate ligands, only the complexes 2 and 3 have been obtained, respectively. Compound 1a, with stoichiometry [Ru2Cl(µ-O2CC6H4-o-OMe)4]n, shows a polymeric structure with the chloride ions bridging the diruthenium units to form linear chains. Compounds 2 and 3, with the same stoichiometry, predictably form zig-zag chains in accordance with their insolubility and their magnetic measurements. Compound 1b, [Ru2Cl(µ-O2CC6H4-o-OMe)4(EtOH)], is a discrete molecular species with a chloride ion and one ethanol molecule occupying the axial positions of the dimetallic unit. Compound 1c is a cation-anion complex, [Ru2(µ-O2CC6H4-o-OMe)4(MeOH)2][Ru2Cl2(µ-O2CC6H4-o-OMe)4]. The cationic complex has two solvent molecules at the axial positions whereas the anionic complex has two chloride ligands at these positions. Complexes have been characterized by elemental analyses, mass spectrometry and IR and UV-vis-NIR spectroscopies. A magnetic study of complexes 1a, 1b, 2 and 3 have also been carried out. The crystal structure of compounds 1b and 1c have been solved by single X-ray crystal methods.

Highly Efficient Single A3-Coupling (Aldehyde-Amine-Alkyne) Reaction Catalyzed by Air Stable Silver-(N-Heterocyclic Carbene) Complexes: Synthesis and Characterization

The interaction of N,N-disubstituted benzimidazolium salts 2a–e with Ag2O formed new silver-(N-heterocyclic carbene) complexes 3a–e. Structural characterization of silver-(N-heterocyclic carbene) complexes was conducted by using NMR, FT-IR and elemental analysis. Preliminary catalytic studies using all the silver complexes 3a–e were performed on three-component coupling reaction of a series of aldehydes with alkynes and amines was demonstrated. Most of these reactions led to formation of the expected propargylamines in good conversions using low amounts catalyst and obviating both the use of purified reagents as employ of a glovebox. Complexes 3a and 3c exhibited good catalytic activities under neat conditions. The silver complexes 3a–e showed luminescence properties in CH3CN at room temperature.