Acetato Complexes Research Articles

Ni(II) and Co(II) Acetato Complexes of Pyrazole-Pyridine Based Ligand: Synthesis, Structure and Thermal Decomposition

Ni(II) and Co(II) Acetato Complexes of Pyrazole-Pyridine Based Ligand: Synthesis, Structure and Thermal Decomposition

Copper based azo dye catalysts for phenoxazinone synthase mimicking efficiency: Structure characterization and bioactivity evaluation

The ligands, 4-(2-Hydroxy-naphthalen-1-ylazo)-N-thiazol-2-yl-benzenesulfonamide (H2TNBS) and N-(3,4-Dimethyl-isoxazol-5-yl)-4-(2-hydroxy-naphthalen-1-ylazo)-benzenesulfonamide (H2INBS), synthesized in the current investigation have been characterized and used for synthesizing divalent copper complexes by their reaction with a number of Cu(II) salts. Spectral and analytical methods have been applied for structures’ investigation. Morphology of the synthesized compounds have been investigated using TEM technique which joint with the results of X-ray powder diffraction spectroscopy confirmed the precipitation of both ligands and their complexes in the nanometric scale. Formation of the synthesized complexes in 1:1 or 2:1 (M:L) ratio was asserted by analytical results. Ultraviolet–visible spectra and magnetic moment were used to demonstrate the geometry around the Cu centers to be 4 coordinated square planar. The compounds under interest have been screened against selected microorganisms including Gram-positive and Gram-negative bacteria, unicellular and multicellular fungus showing, in most compounds, enhancement of activity upon chelation. The cell lines A-549 (human lung cancer cell line) and Panc-1 (human pancreatic cancer cell line) have been chosen to check the antitumor efficiency of the synthesized compounds; Vinblastine was used as standard. Finally, the Cu(II) chelates were investigated toward mimicking the protein phenoxazinone synthase using o- aminophenol (OAP) as substrate and DMF is the solvent. The results presented extremely high activity for the chloro complex 4 and nitro complex 6 with TOF numbers from 390.48 and 467.01 h−1, respectively. The least activity afforded by the acetato complexes 2 and 5.

Ni(II) and Co(II) acetato complexes of pyrazole-pyridine based ligand: synthesis, structure and thermal decomposition

Two novel acetato complexes with NNN type planar bdmpp ligand, [Ni(OAc)(H2O)2(bdmpp)]OAc (1) [Co(OAc)(H2O)2(bdmpp)]OAc (2) (bdmpp: 2,6-bis(3,5-dimethylpyrazolyl)pyridine) were synthesized and characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction analysis. Thermal stabilities of these complexes were studied by thermogravimetric (TG) and differential thermal analyses (DTA). The crystal structures of both complexes were also determined using single-crystal X-ray diffraction. It was found that, complexes 1 and 2 possessed smilar octahedral coordination environment in which, metal ions were coordinated by N donor atoms of bdmpp, two oxygens of aqua ligands and one oxygen atom from terminal bonding acetato ligand.

Mono- and bimetallic complexes of pyrazolone based ligand: Synthesis, characterization, antitumor and molecular docking studies

Cu(II), Ni(II), Co(II) and Mn(II) chloro in addition to Cu(II) acetato complexes of the ligand termed 3-amino-4-(2-(3-chlorophenyl)hydrazono)-1H-pyrazol-5(4H)-one (abbreviated as ACHP) have been isolated. The structural features and geometrical arrangements of the synthesized complexes have been identified through applying alternative analytical and spectroscopic tools including elemental analysis, FTIR, conductivity measurements, UV–vis spectra, magnetic moment measurements and thermogravimetric (TG/DTG) techniques. The applied tools joint together confirmed the formation of the metal complexes in the molar ratio 1:1 (L:M) for Cu(II) and Co(II) complexes and 1:2 (L:M) ratio for both of Ni(II) and Mn(II) chelates. The applied spectral techniques also confirmed the metal chelates to have the formulae [Cu(ACHP)Cl2]·0.5H2O, [Cu(ACHP)(CH3COO)2], [Ni2(ACHP)Cl2(H2O)2]·Cl2, [Co(ACHP)Cl2]·0.5H2O and [Mn2(ACHP)Cl4]. UV–Vis spectra and µeff values of the metal chelates assured the geometry around the metal ion center to be tetrahedral for all the metal complexes except Cu(II) chloro and acetato complexes which afforded square planar and octahedral geometries, respectively. The molecular docking studies have been performed using 3s7s and 5cei, the co-crystal structures of proteins for breast (MCF-7) and colon (HCT-116) cancer cells, respectively, in addition to the antitumor activity investigations contra the two types of tumor cells.

Outstanding in-situ CNTs on Fe-pillared nanoclay for high-performance polymer nanocomposites

The successful and novel synthesis of in-situ multi-walled carbon nanotubes (MWCNTs) on a pillared montmorillonite (Mt) nanoclay was achieved. These novel nanofillers were mixed with poly(methyl methacrylate) (PMMA) polymer to study electrical properties of these nanocomposites. The trinuclear Fe (III)-acetato complex, [Fe3(OOCCH3)7·OH·nH2O]+NO3−, was synthesized and analyzed by chemical analysis and FTIR spectroscopy, and was used as the precursor for the CNT synthesis. The complex proved to be an excellent precursor for the synthesis of CNTs. CNT-clay hybrid nanofillers with varying CNT contents and qualities were observed and investigated using XRD, TGA, XPS, Raman, SEM, and TEM. The ID/IG of CNTs decreased from 1.92 for 0.5 CEC of the iron complex to 0.72 for 6 CEC CNTs. The XRD indicated that Mt. layers were intercalated with iron species during the ion-exchange process, and further exfoliated due to the growth of CNTs. The synthesis yield increased at higher iron concentrations, i.e., 83.4% for 6 CEC CNTs. The 6, 7, and 8 CEC CNTs exhibited smaller diameter CNTs, 14.6 (±4.4), 18.2 (±4.4), and 16.5 (±6) nanometers, when compared to those of lower catalyst concentrations. The 8 CEC CNTs showed 3.5 S m−1 of conductivity, and ~ 90% of the sp2 structure. The electrical properties of PMMA nanocomposites showed these these CNT-clay hybrid fillers are effective for charge storage applications.

Comparative stability, cytotoxicity and anti-leishmanial activity of analogous organometallic Sb(V) and Bi(V) acetato complexes: Sb confirms potential while Bi fails the test

A series of sixteen triphenyl Bi(V) and Sb(V) acetato complexes of general formula [MPh3(O2CCR)2] and one oxido-bridge antimony complex [(SbPh3(O2COC(O)Me))2O], have been synthesised and characterised, thirteen of which are novel. The solid-state structures of fifteen of the complexes have been successfully authenticated by single crystal X-ray diffraction. All structures, excluding the oxido-bridge antimony complex, adopt a typical trigonal bipyramidal confirmation with the phenyl rings in a propeller-like orientation in the equatorial plane. Fourteen of the complexes were screened for their anti-leishmanial activity and cytotoxicity towards mammalian cells. The Bi(V) complexes were found to be unstable in DMEM culture media and to be severely toxic towards mammalian cells, with IC50 values in the range 11.4 μM–19.8 μM. In contrast, the Sb(V) complexes demonstrated a high degree of stability and selectivity, with IC50 values 6.18–19.1 μM for the promastigote assay, and of 73.8–≤100 μM for the human fibroblasts. Assessment of the Sb(V) complexes against the clinically relevant amastigote form of these parasites at 10 μM showed all but the oxido-bridged complex to be effective, with % infection values ranging from 7.0 ± 1.7–40.5 ± 2.0.

Coordination Chemistry of the PdmBOX Pincer Ligand: Reactivity at the Metal and the Ligand

The coordination chemistry of PdmBOX [2,5‐bis(2‐oxazolinyldimethylmethyl)pyrrole] pincer ligands, in which a dimethylmethylidene linker has been introduced to preclude rearrangements in the backbone, has been studied with 3d and 4d late transition metals. The in situ lithiated PdmBOX ligand was treated with MnCl2, FeCl2 and CoCl2 to give [iPr(PdmBOX)MCl] (M = Mn: 2; Fe: 3; Co: 4) which were found to adopt a distorted tetrahedral coordination geometry in the crystal. Addition of 2,6‐dimethylphenylisocyanide to 3 gave the diamagnetic tris(isocyanide) derivative [iPr(PdmBOX)Fe(CNxyl)3]Cl (5) with the chloride as the counteranion. Complexes 2–4 were found to be precatalysts for the enantioselective hydrosilylation and hydroboration of acetophenone. The synthesis of PdmBOX‐palladium(II) complexes was achieved by deprotonation of the protioligand with potassium bis(trimethylsilyl)amide (KHMDS) and subsequent reaction with [(cod)PdCl2] giving [iPr(PdmBOX)PdCl] (6) or by stirring (S)‐iPr(PdmBOX)H with palladium acetate yielding the palladium acetato complex 7. Treatment of the latter with phenylsilane at 60 °C also led to the slow formation of the metal hydride complex which was the key species in the catalytic hydrosilylation of styrene oxide, albeit with low activity. The coordination of (S)‐iPr(PdmBOX)H to rhodium(I) was accomplished by reaction with (acetylacetonato)dicarbonylrhodium(I) to give the corresponding PdmBOX‐Rh complex 8 which reacted with methyl iodide to give the octahedrally coordinated rhodium(III) complex [iPr(PdmBOX)Rh(CH3)I(CO)] 9. Reaction of 8 with one equivalent of CsBr3 led to the full conversion to the dibromorhodium(III) complex [iPr(PdmBOX)Rh(CO)Br2] 10. Upon reaction of 10 with N‐bromosuccinimide (NBS), the pyrrole backbone in 10 was brominated to give complex 11. In a similar way, a selective conversion of [iPr(PdmBOX)NiCl] to the backbone‐chlorinated [iPr(ClPdmBOX)NiCl] (12) was achieved by the treatment with N‐chlorosuccinimide.

Kinetics and Mechanistic Insights into the Acetate-Assisted Dimerization of Terminal Alkynes under Ruthenium- and Acid-Promoted (RAP) Catalysis

The mechanism of the dimerization of terminal aryl alkynes promoted by [{RuCl(μ-Cl)(η6-p-cymene)}2](1)/AcOH, under cooperative transition metal/Bronsted acid catalysis, has been investigated with regard to (i) the activation of the dinuclear ruthenium complex and (ii) the catalytic formation of the trans-1,4-diaryl-1,3-enyne products, by a detailed kinetic investigation of both processes. Complex 1 is subject to a slow solvolytic process in neat acetic acid or is transformed rapidly in the presence of sodium acetate to form the monomeric ruthenium(II) acetato complex [RuCl(η6-p-cymene)(OAc)]. The latter is the active catalytic species promoting the alkyne dimerization process, via initial π-alkyne coordination and intramolecular C–H abstraction by the acetate ligand, as key steps of the catalytic cycle. The presence of additive acetate salts allows for the reaction to proceed at room temperature with short reaction times and high trans/cis stereoselectivity, thus rendering this catalytic system among the ...

A Raman Spectroscopic Study of Aqueous La(CH3CO2)3 Solutions and La(CH3CO2)3·1.5 H2O(cr)

Aqueous solutions of La(CH3CO2)3, NaCH3CO2 and La(ClO4)3 were studied using Raman spectroscopy. In dilute NaCH3CO2 solution, acetate is fully hydrated and forms only minor amounts of ion pairs. The characteristic Raman bands are discussed and assigned. In fairly dilute La(ClO4)3 solutions, the La3+(aq) ion occurs as the nonahydrate. The separation of the carboxylate bands, νas – νs (Δ-value), in NaCH3CO2(cr) compared to La(CH3CO2)3·1.5H2O(cr) correlates with the bonding type of acetate which is “ionic” in the former but bidentate chelating/tridentate chelating in the latter. Other acetate bands such as the deformation mode of the CO2 moiety, δ CO2, and the two rocking vibrations (ρ), as well as the C–C stretch show marked differences in their band positions in NaCH3CO2(cr) compared to the ones in La(CH3CO2)3·1.5H2O(aq). In a ternary solution of La(CH3CO2)3/LaCl3 with a molar ratio La3+(aq): $$ {\text{CH}}_{3} {\text{CO}}_{2}^{ - } $$ (aq) = 3.87: 1.00), the bands of the bound acetate on La3+ were characterized and compared to those of fully hydrated acetate, $$ {\text{CH}}_{3} {\text{CO}}_{2}^{ - } \left( {\text{aq}} \right) $$ . In this solution, almost all acetate is ligated to La3+ in a bidentate fashion and two complex species could be identified (molar ratios La3+: $$ {\text{CH}}_{3} {\text{CO}}_{2}^{ - } $$ = 1:1 and 1:2, respectively). In La(CH3CO2)3 solutions in H2O and D2O strong acetato complexes are formed and the bands of the bound acetate were characterized and compared with the ones of the fully hydrated acetate modes. A dilution series down to 0.0037 mol·L−1 in La(CH3CO2)3(aq) and to 0.0150 mol·L−1 in La(CH3CO2)3(D2O) showed that two acetate complexes are formed in these solutions. Again, it was shown that in these solutions the bound acetates on La3+ exist as bidentate ligands. DFT frequencies of the acetate on clusters {La(OH2)7O2CCH3)}2+ and {La(OH2)5(O2CCH3)2}+ compared well with the measured values. By determining the ligation number, $$ \bar{n} $$ , it can be established that in dilute solutions, below 0.04 mol·L−1, a complex with a 1:1 stoichiometry (La3+: $$ {\text{CH}}_{3} {\text{CO}}_{2}^{ - } $$ ) exists in equilibrium with “free” acetate while in more concentrated solutions a 1:2 complex also forms. La3+(aq) hydrolysis is slight and very small equilibrium concentrations of CH3COOH were detected (C–C stretch at 893 cm−1). From quantitative Raman measurements, K 1 was determined to be 160 ± 10 at 22 °C.

A New Mixed‐Valent Copper Cyanido Complex and a New Copper(II) Acetato Complex, Prepared with an Ionic Liquid

AbstractWhen copper(II) acetate is treated with the ionic liquid n‐butylmethylimidazolium cyanide (BMIm‐CN), in ethanol solution, two new copper coordination compounds are obtained. (BMIm)2[Cu4(CN)7] comprises a 3D coordination polymer of cyanide bridged copper ions. This anionic coordination polymer contains CuI as well as CuII ions, i.e. it is a mixed‐valent compound. The polymer can be described as honeycomb structure with the BMIm+ cation being located in the cages. The second compound obtained from the chemical reaction is (BMIm)[Cu2(OAc)5][Cu(OAc)2(H2O)]2·C2H5OH, which can be described as double‐salt. The first unit (BMIm)[Cu2(OAc)5] contains paddle wheel copper(II) acetato moieties, which are bridged by additional acetato ligands and form infinite chains. The second part of the double salt is the neutral, [Cu(OAc)2(H2O)]2 complex. These two parts as well as the co‐crystallized ethanol molecule are connected through a network of hydrogen bridges.

Studies on the photoredox behavior of copper(II) acetato complexes with tripodal 4N ligands in methanol solution

The reactivity of copper(II) acetate complexes carrying the fully methylated tris(2-aminoethyl)amine ligand Me6tren under UV- and visible-light irradiation was studied in methanol solution. In the presence of water, the formation of colloidal copper nanoparticles occurred, indicating an irreversible decomposition of the copper(II) precursor under UV-light exposure. In dry methanol, a photoredox reaction involving the acetate ligand was observed, which leads to intermediate copper(I) complex formation. The potential of these processes for photocatalytic applications is briefly discussed and evaluated.

Gold and Palladium Hetero-Bis-NHC Complexes: Characterizations, Correlations, and Ligand Redistributions

A series of new Au(I) hetero-bis-NHC complexes [Au(iPr2-bimy)(NHC)]X (X = BF4, PF6, 2–6) and the hetero-tetrakis-NHC complex [Au2(iPr2-bimy)2(μ-ditz)](BF4)2 (7) have been synthesized using the Au(I) acetato complex [Au(O2CCH3)(iPr2-bimy)] (C) as a basic metal precursor (iPr2-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene, ditz = 1,2,4-triazolidine-3,5-diylidene). The Au(III) hetero-bis-NHC complex trans-[AuCl2(iPr2-bimy)(Bn2-bimy)]BF4 (12; Bn2-bimy = 1,3-dibenzylbenzimidazolin-2-ylidene) and the hetero-tetrakis-NHC complex all-trans-[Au2Cl4(iPr2-bimy)2(μ-ditz)](BF4)2 (13) were obtained by oxidation of their corresponding Au(I) hetero-NHC precursors. For all Au(I) hetero-NHC complexes, the 13C carbene signals of the constant iPr2-bimy ligand are found to be highly correlated with those in Pd(II) analogues of the type trans-[PdBr2(iPr2-bimy)(NHC)], which could be applied to detect the σ-donating ability of the trans-standing NHC. In addition, an interesting ligand redistribution process was observed for some of the Au(I) hetero-bis-NHC complexes.

Synthesis and Structure of a Trinuclear Pd–Ag–Pd Carbene Acetato Complex

AbstractWe describe the synthesis and the solid‐state structure of a trinuclear Pd–Ag–Pd carbene acetato complex. The structure was determined by single‐crystal X‐ray experiments [P21/n (no. 14) a = 12.0241(4), b = 25.7201(10), c = 21.3564(8) Å, β = 93.841(2)°, V = 6589.9(4) Å3, Z = 4, R1 = 0.0319, wR2 = 0.0721]. The complex consists of two palladium biscarbene units connected to a silver atom by bridging acetate ions with Pd–Ag bond lengths of 2.89 Å, which are shorter than the sum of the van der Waals radii. Additionally the 13C NMR shifts of the carbene carbon atoms indicate that a palladium silver interaction is present. The repeat unit in the unit cell contains one complex and an infinite chain of two water molecules, one acetic acid and one acetate ion. We show that the hydrogen bond between the complex and a water molecule is the reason for the distorted arrangement.

Synthesis and structure of trans-bis(1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene)palladium(II) dichloride and diacetate. Suzuki–Miyaura coupling of polybromoarenes with high catalytic turnover efficiencies

trans-Bis(1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene)palladium(II) dichloride has been shown to be an excellent catalyst for the multiple Suzuki–Miyaura coupling reactions of polybromoarenes to the corresponding fully substituted polyarylarenes. The reactions proceeded in excellent yields and with high turnover numbers. With 1,4-dibromobenzene the catalyst was found to be active for up to 13 consecutive cycles with a turnover number of 1260. The polyarylarenes were obtained in pure form after crystallization once without recourse to chromatographic purification. The single-crystal X-ray structures of the chloro (1) as well as the corresponding acetato (2) complexes are also reported and compared with the corresponding complexes of 1,4-diphenyl-3-methyl-1,2,3-triazol-5-ylidene as the ligand.

Dimethylaminoalkylchalcogenolate complexes of palladium(II): Synthesis, structures, and their catalytic activity in Suzuki C–C cross-coupling reactions

The reaction of [PdCl(E∩N)]n with AgOAc in methanol afforded the corresponding acetato complexes, [Pd(OAc)(E∩N)]n (E∩N/n = ECH2CH2NMe2/3; ECH2CH2CH2NMe2/2 (E = S or Se)). The molecular structures of [Pd(OAc)(ECH2CH2NMe2)]3 were established by single crystal X-ray diffraction analyses. The trimeric structures comprise of three palladium atoms bridged through chalcogen atoms of the chelating chalcogenolate ligand forming a twisted six-membered Pd3E3 ring. The acetato-ligand acts in a monodentate fashion. The catalytic activity of [PdCl(E∩N)]n and [Pd(OAc)(E∩N)]n in Suzuki C–C cross coupling reactions has been investigated. The dimeric acetato complexes showed the best activity in dioxane.

Ortho Palladation of the Phenethylamines of Biological Relevance l-Tyrosine Methyl Ester and Homoveratrylamine. Reactivity of the Palladacycles toward CO and Isocyanides. Synthesis of the Natural Alkaloid Corydaldine

Palladacycles derived from l-tyrosine methyl ester, (S)-[Pd2{C,N-C6H3CH2CH(CO2Me)NH2-2,(OH)-4}2(μ-Br)2] (1a-Br), and homoveratrylamine, [Pd2{C,N-C6H2CH2CH2NH2-6,(OMe)2-3,4}2(μ-Br)2] (1b-Br), can be easily prepared in good yield by reacting Pd(OAc)2, the corresponding ammonium triflate, and NaBr. Under the same conditions, the reaction of Pd(OAc)2 with the free amine affords a low yield of the corresponding acetato complex 1a-OAc or 1b-OAc (the latter only detected in solution). In our hands, the previously reported palladation at the C2 position of homoveratrylamine with Pd(OAc)2 is not observed. Instead, a complex mixture is obtained, mainly containing [Pd(OAc)2{NH2CH2CH2C6H3(OMe)2-3,4}2] and minor amounts of 1b-OAc, which reacts with NaBr to afford a new mixture from which [PdBr2{NH2CH2CH2C6H3(OMe)2-3,4}2] can be isolated and characterized. These and other adducts can be isolated from Pd(OAc)2, homoveratrylamine, and various ligands (PPh3 and Br–). 6-Bromohomoveratrylamine reacts with Pd(dba)2 in the presence of tmeda to give the complex [Pd{C,N-C6H2CH2CH2NH2-6,(OMe)2-3,4}(tmeda)]Br. Reactions of complexes 1 with acetylacetonato or neutral (PR3) ligands give products resulting from substitution or bridge-splitting reactions. While 1a-Br reacts with XyNC (1:2 molar ratio) to give (S)-[Pd{C,N-C6H3CH2CH(CO2Me)NH2-2,(OH)-4}Br(CNXy)], 1b-Br gives [Pd{C,N-C(═NXy)-C6H2CH2CH2NH2-6,(OMe)2-3,4}Br(CNXy)]. (S)-7-Hydroxy-3-(methoxycarbonyl)-3,4-dihydroisoquinolin-1(2H)-one and 6,7-dimethoxy-3,4-dihydroisoquinolin-1(2H)-one (corydaldine) have been synthesized through the stoichiometric carbonylation of palladacycles 1a-Br and 1b-Br. The crystal structures of a solvento intermediate in the ortho-metalation reaction of the triflate derivative of l-tyrosine methyl ester and four other complexes have been determined by X-ray diffraction studies.

Reactivity of Scandium β-Diketiminate Alkyl Complexes with Carbon Dioxide

The reactions of two highly air- and moisture-sensitive scandium bis(alkyls) supported by a bulky β-diketiminato (nacnac) ligand with carbon dioxide are described. [κ2-ArNC(tBu)CHC(tBu)NAr]ScR2 (Ar = 2,6-iPr2C6H3; R = CH3, 1a; R = CH2SiMe3, 1b) react rapidly with CO2 to give mixtures of mono- and bis(carboxylato) insertion products 2a/2b and 3a/3b depending on the stoichiometry and conditions of the reaction. Compound 2a (R = CH3) is a dimeric complex with bridging acetato groups, as determined by X-ray crystallography. These compounds were characterized by NMR spectroscopy, and 3a could be isolated in pure form. Treatment of these compounds with excess CO2 resulted in addition to the central carbon of the Sc(nacnac) six-membered ring and displacement of the nitrogen donors to yield dimeric scandium carboxylates 4a/4b; compound 4b was characterized by X-ray crystallography. Reactions of the nacnac scandium cations formed upon abstraction of one or two methides from 1a using B(C6F5)3 with CO2 were also explored. Although the products were qualitatively more thermally robust, eventually ligand displacement occurred in these cationic acetato complexes as well. Nevertheless, insertion products were characterizable in solution using NMR spectroscopy. Overall, this study shows the facility with which CO2 is taken up by scandium alkyls but that the nacnac ligand framework is too reactive to support chemistry aimed at catalytic conversion of CO2 into other products.

Dimerization of Terminal Arylalkynes in Aqueous Medium by Ruthenium and Acid Promoted (RAP) Catalysis: Acetate‐ Assisted (sp)C(sp2)C Bond Formation

AbstractThe hexamethylbenzene ruthenium(II) dimer [{RuCl(μ‐Cl)(η6‐C6Me6)}]2 (5 mol%), tested among a series of ruthenium(II) and ruthenium(IV) complexes, represents an efficient precatalyst source for the dimerization of terminal arylalkynes ArCCH [Ar=C6H5, 3,4,5‐(OMe)3C6H2, 4‐MeOC6H4, 2‐MeOC6H4, 4‐MeC6H4, 2,4,5‐Me3C6H2, 4‐BrC6H4, 4‐ClC6H4, 4‐FC6H4, 4‐HC(O)C6H4, 4‐CH2CHC6H4, 3‐NCC6H4, 4‐O2NC6H4, 4‐EtO2C‐(CH2)3OC6H4, 4‐HO(CH2CH2O)3C6H4, 3‐HO(CH2CH2O)3‐C6H4] in acetic acid/water mixture (1:1, v/v). The reactions proceed for 24 h at room temperature under heterogeneous conditions and afford the dimeric enyne derivatives (E)‐ArCHCHCCAr in high yields and stereoselectivity. The preformed acetato complex [RuCl(η6‐C6Me6)(κ2‐OAc)] catalyzes the dimerization of phenylacetylene under analogous conditions, with rapid substrate conversion. The presence of cosolvents of acetic acid different from water reduces dramatically the efficiency and selectivity of the reaction. The aqueous medium facilitates the activation stage of the precatalyst by assisting the splitting of the ruthenium dimer. The addition or generation in situ of acetate salts results in shorter reactions times (0.5–3 h) and excellent yields, due to the rapid formation of active acetato complexes. Circumstantial evidence indicates that the π‐bound alkyne molecule is activated by intramolecular proton abstraction. This is currently the most efficient, E‐selective and wide‐scope catalytic system for the alkyne dimerization reaction in protic aqueous media.

Sulfur containing platinum(ii) complexes with N-heterocyclic carbene ligands obtained by reactions of a hydrosulfido complex

A hydrosulfido platinum(ii) complex with a chelated N-heterocyclic carbene (NHC) ligand was oxidised with O(2) in the presence of excess hydrogen sulfide, to give a linear tetrasulfido complex, and without hydrogen sulfide, to give a thiosulfato-bridged dinuclear complex. The hydrosulfido complex also reacted with an acetato complex containing the chelating NHC platinum unit to afford a trinuclear platinum complex with two triply bridging sulfido ligands showing an equilibrium in solution between two isomers based on the arrangement of the chelating NHC ligands.

Synthesis, spectroscopic, antimicrobial, DNA binding and cleavage studies of some metal complexes involving symmetrical bidentate N, N donor Schiff base ligand

The Schiff base ligand, N, N′-bis-(4-isopropylbenzaldimine)-1,2-diaminoethane (L), obtained by the condensation of 4-isopropylbenzaldehyde and 1,2-diaminoethane, has been used to synthesize the complexes of the type [ML 2X 2] [M = Co(II), Ni(II) and Zn(II); X = Cl and OAc]. The newly synthesized ligand (L) and its complexes have been characterized on the basis of elemental analyses, mass, 1H and 13C-NMR, molar conductance, IR, UV–vis, magnetic moment, CV and thermal analyses, powder XRD and SEM. IR spectral data show that the ligand is coordinated to the metal ions in a bidentate manner. The geometrical structures of these complexes are found to be octahedral. Interestingly, reaction with Cu(II) ion with this ligand undergoes hydrolytic cleavage to form ethylenediamine copper(II) complex and the corresponding aldehyde. The antimicrobial results indicate that the chloro complexes exhibit more activity than the acetato complexes. The complexes bind to CT–DNA by intercalation modes. Novel chloroform soluble ZnL 2Cl 2 complex exhibits tremendous antimicrobial, DNA binding and cleaving properties.