Thermolysis of polynuclear platinum(II) acetamidato complexes

The thermolysis of five polynuclear Pt(II) acetamidato complexes with known structures (I-V) and platinum blue of the composition Pt(NHCOCH₃)₂ · H₂O prepared by two different procedures (VI and VIa) has been studied by differential scanning calorimetry and thermogravimetry. The results of studying the thermolysis of these complexes allows one to assume that the structures of VI and VIa are different: complex VI is polynuclear and consists of binuclear fragments[(H₂O)(NHCOCH₃)Pt(μ-NHCOCH₃)₂Pt(NHCOCH₃)(H₂O)], whereas complex VIa is built of fragments [(H₂O)(NHCOCH₃)Pt(μ-OH)(μ-OH)(μ-NHCOCH₃)Pt(NHCOCH₃)₂].     

Crystal Structures,Cytotoxicity, Cell Apoptosis Mechanism,and DNA Binding of Two 8-Hydroxylquinoline Zinc(II) Complexes

Two zinc(II) complexes, [Zn₄(HOQ)₆Ac₂] (I) (HOQ = 8-hydroxylquinoline) and [Zn₄(MeQ)₆Ac₂] (II) (MeQ = 2-methyl-8-hydroxylquinoline), were synthesized and characterized by IR spectroscopy, ESI-MS spectrometry, elemental analysis and single crystal X-ray diffraction analysis (CIF files CCDC nos. 1433544 (I) and 1433546 (II)). The in vitro cytotoxicity of the two complexes, which was first reported, was evaluated by MTT assay against a series of tumor cell lines as well as HL-7702 normal liver cell line. The results indicated that they showed significantly higher cytotoxicity than cispltain on BEL-7404 cells with IC₅₀ values of 11.85 ± 0.06 μM (I) and 8.40 ± 0.07 μM (II), respectively. Further apoptosis mechanism studies on BEL-7404 cells suggested that their antitumor activities were achieved through cell apoptosis and arrest at G1 or S phase. The decline of mitochondrial membrane potential, the elevation of reactive oxygen species and cytoplasmic calcium concentration ([Ca²⁺]_c), the raise of caspase-3/9 activity indicated that complexes I and II induced apoptosis of BEL-7404 by a mitochondrial dysfunction pathway. Investigations on the binding properties of complexes I and II to ct-DNA by UV-Vis, circular dichroism spectra and agarose gel electrophoresis indicated that the two complexes could bind with ct-DNA via an intercalative mode.     

Substitution of aqua ligands from <Emphasis Type="Italic">cis</Emphasis>-platinum(II) complexes bearing 2-(phenylthiomethyl)pyridine spectator ligands

Cis-Pt(II) complexes, namely [Pt{2-(phenylthiomethyl)pyridine}(H₂O)₂](CF₃SO₃)₂ Pt(pyS ^Ph ), [Pt{2-(4-tert-butylphenylthiomethyl)pyridine}(H₂O)₂](CF₃SO₃)₂ Pt(pyS ^{Ph( t -But)} ) and [Pt{2-(4-fluorophenylthiomethyl)pyridine}(H₂O)₂](CF₃SO₃)₂ Pt(pyS ^PhF ), were synthesised and characterised. The pK _a1 and pK _a2 values of the complexes were determined titrimetrically. Substitution of the aqua ligands from these complexes by thiourea nucleophiles was studied at a pH of 2 and ionic strength of 0.1 M under pseudo-first-order conditions using stopped-flow and UV–visible spectrophotometric techniques. Substitution of the aqua ligands depends on both the nature and concentration of the incoming ligand, with low enthalpy and negative entropy of activation values. Substitution of the first and second aqua ligands occurs sequentially and fits the rate laws: k _{obs (1/2)} = k _(1/2) [Nu]. The second-order rate constant, k ₁, relates to the substitution trans to sulphur, while k ₂ is the second-order rate constant for the subsequent substitution of the aqua ligand trans to pyridine. The rate of substitution of the first aqua ligand decreases in the order: Pt(pyS ^{Ph( t -But)} ) > Pt(pyS ^PhF ) > Pt(pyS ^Ph ), while that of the second decreases in the order: Pt(pyS ^{Ph( t -But)} ) > Pt(pyS ^Ph ) > Pt(pyS ^PhF ), reflecting the influence of the substituents on the spectator ligands. ¹⁹⁵Pt NMR spectra of aged solutions of complexes with the thiourea nucleophile suggest a subsequent but rapid concentration-independent ring opening of the N,S-bidentate ligand to form a PtS ₄ species. The crystal structure of Pt(pyS ^PhF )Cl ₂ was elucidated by X-ray diffraction analysis.     

Study on the interaction of three structurally related cationic Pt(II) complexes with human serum albumin: importance of binding affinity and denaturing properties

Human serum albumin (HSA) primarily functions as a transport carrier for a vast variety of natural ligands and pharmaceutical drugs. In the present study, three structurally related cationic Pt(II) complexes ([Pt(ppy)(dppe)]CF₃CO₂: 1, Pt(bhq)(dppe)]CF₃CO₂: 2, and [Pt(bhq)(dppf)]CF₃CO₂: 3) were used to evaluate their interaction with HSA under different experimental setups, using UV–Vis absorption spectroscopy, fluorescence and circular dichroism techniques. The spectroscopic results suggest that upon binding to HSA, the Pt(II) complexes could effectively induce structural alteration of the protein. The complexes can bind to HSA with the binding affinities of the following order: 3 > 2 > 1. Also, thermodynamic parameters of binding between these complexes and HSA indicated the existence of entropy-driven spontaneous interaction which primarily dominated with the hydrophobic forces. Also, docking simulation study revealed the binding details of these complexes on HSA. Complex 3 with highest binding affinity for HSA indicates lowest denaturing effect on this protein. The low denaturation properties of 3 appear important in the terms of lower susceptibility of this platinum complex for possible development of deleterious side effects.     

Syntheses,structures, and solid-state phosphorescence characteristics of <Emphasis Type="Italic">trans</Emphasis>-bis(salicylaldiminato)Pt(II) complexes bearing perpendicular <Emphasis Type="Italic">N</Emphasis>-aryl functionalities

The syntheses, structures, and solid-state emission characteristics of trans-bis(salicylaldiminato)Pt(II) complexes bearing N-aromatic functionalities are described herein. A series of Pt complexes bearing various N-phenyl (1) and N-(1-naphthyl) (2) groups on the salicylaldiminato ligands were prepared by reacting PtCl₂(CH₃CN)₂ with the corresponding N-salicylidene aromatic amines, and the trans-coordination and crystal packing of these complexes were unequivocally established based on X-ray diffraction (XRD). Complexes with 2,6-dimethylphenyl (1c), 2,6-diisopropylphenyl (1d), 1-naphthyl (2a), and 1-(2-methylnaphthyl) (2b) groups on the N atoms exhibited intense phosphorescent emission at ambient temperature in the crystalline state, while those with phenyl (1a), 2,6-dibromophenyl (1b), and 2,6-bis(N,N-dimethylamino)phenyl (1e) functionalities were either less emissive or non-emissive under the same conditions. XRD analyses identified significant intramolecular interactions between Pt and H atoms of the N-aryl functionalities in the emissive crystals of 1c, 1d, and 2a. These interactions were evidently an important factor associated with intense emission at ambient temperature.     

Synthesis and molecular structures of tris(thio- and selenophenyl)stannyl complexes of cyclopentadienylcarbonylnitrosylmanganese and their reaction products with tungsten carbony

Reactions of CpMn(CO)(NO)SnCl₃ (I) with sodium benzenethiolate and sodium benzenesele-nolate gave orange crystals of the complexes CpMn(CO)(NO)Sn(EPh)₃, where E = S (II) or Se (III). Treatment of complex II with photochemically generated W(CO)₅(THF) yielded the adduct CpMn(CO)(NO)Sn(SPh)₃ · W(CO)₅ (IV). A similar treatment of complex III resulted in the formation of the ditungsten complex W₂(CO)₄(SePh)₆ (V) with transfer of all chalcogenate groups from tin to tungsten. In reactions of complexes II and III with a Pt₀ complex with phosphine and acetylene, (PPh₃)₂Pt(Ph₂C₂), the chalcogenate groups are transferred from tin. Only the known Pt(II) complexes (PPh₃)₂Pt(EPh)₂), where E= S (VI) or Se (VII). Molecular structures IV and V were characterized by X-ray diffraction. It has been found that the Mn-Sn bond in complex IV (2.5479(9) Å) is nearly the same length as that found earlier for complex II (2.5328(17) Å) and is substantially shorter than the sum of the covalent radii of Mn and Sn (2.78 Å). The Sn-S bond is noticeably lengthened (2.5217(11) Å) only for the S atom bound to tungsten (W-S, 2.5696(12) Å), while the other Sn-S bonds (2.4413(12) and 2.4291(12) Å) are virtually the same as in complex II (on average, 2.441 Å). Complex V contains the direct W-W bond (2.8153(16) Å) supplemented with four benzeneselenolate bridges in which the W-Se bonds (on average, 2.642(2) Å) are longer than the two terminal W-SePh bonds (2.571(2) Å). All the W-Se bonds are much shorter than the sum of the covalent radii of W and Se (2.82 Å).     

The role of substituents in a bidentate <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-chelating ligand on the substitution of aqua ligands from mononuclear Pt(II) complexes

The rate of substitution of aqua ligands from three mononuclear platinum(II) complexes, namely [Pt{2-(pyrazol-1-ylmethyl)pyridine}(H₂O)₂](ClO₄)₂, [Pt(H ₂ Py)]; [Pt{2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine}(H₂O)₂](ClO₄)₂, [Pt(dCH ₃ Py)] and [Pt{2-[(3,5-bis(trifluoromethyl)pyrazoly-1-ylmethyl]pyridine}(H₂O)₂](ClO₄)₂, [Pt(dCF ₃ Py)] by thiourea, N,N-dimethylthiourea and N,N,N′,N′-tetramethylthiourea, was studied in aqueous perchloric acid medium of constant ionic strength. The substitution reactions were investigated under pseudo-first-order conditions as a function of nucleophile concentration and temperature using UV/Visible and stopped-flow spectrophotometries. The observed pseudo-first-order rate constants, \( k_{{{\text{obs }}\left( {1/2} \right)}} \), for the stepwise substitution of the first and second aqua ligands obeyed the rate law: \( k_{{{\text{obs}}\left( {1/2} \right)}} = k_{{2 \left( { 1 {\text{st/2nd}}} \right)}} \left[ {\text{Nu}} \right] \). The first substitution reaction takes place trans to the pyrazole ligand, while the second entering nucleophile is stabilised at the reaction site trans to the pyridine ligand. The rate of substitution of the first aqua ligand from the complexes followed the order: Pt(dCF ₃ Py) > Pt(H ₂ Py) > Pt(dCH ₃ Py), while that of the second was Pt(H ₂ Py) ≈ Pt(dCF ₃ Py) > Pt(dCH ₃ Py). Lower pK _a values were found for the deprotonation of the aqua ligand cis to the pyrazole ring. Density functional theory calculations were performed to support the interpretation of the experimental results.     

Cobalt(III) complexes with biguanide derivatives: Synthesis,structures, and antiviral activity

Three Co(III) complexes with biguanide derivatives [Co(NH₂C(=NH)NHC(=NH)NR¹R²)₃]Cl₃ (R¹R² = Me₂ (I), Et₂ (II), and H^sBu (III)) were obtained and characterized by elemental analysis, IR spectroscopy, and electronic absorption spectroscopy. Structure III was confirmed by X-ray diffraction (CIF file CCDC no. 1401783). Complexes I–III and [M(SC(NH₂)₂)₄]Cl₂ (M = Pd, Pt, and [Co(En)₃]Cl₃) were tested for in vitro antiviral activity against the A/California/07/09 (H1N1pdm09) influenza virus. The best results were achieved with complex III and both thiourea complexes.     

Mono-, Di- and Tetranuclear Complexes and Clusters With Bromine-Functionalized Bis(diphenylphosphino)amine Ligands

We report the preparation of bromo-aryl functionalized bis(diphenylphosphino)amine ligands of the type Ph₂PNArPPh₂ (1, Ar = p-BrC₆H₄; 2, Ar = p-BrC₆H₄–C₆H₄) and their coordination properties. Mono- and dinuclear complexes were formed with Cu(I), Au(I), Pd(II), Pt(II) and tetranuclear cobalt carbonyl clusters were obtained. The crystal structures of [PdCl₂(1)] (3), [PdCl₂(2)] (4), [(AuCl)(μ-1)] (6), [Co₄(CO)₅(μ-CO)₃(μ-dppa)(μ-1)] (dppa = Ph₂PNHPPh₂) (8) and [Co₄(CO)₅(μ-CO)₃(μ-dppm)(μ-1)] (dppm = Ph₂PCH₂PPh₂) (9) have been determined by X-ray diffraction. Whereas the diphosphine ligands chelate the metal center in 3 and 4, and in the Pt(II) complex 5 which is analogous to 3, ligand 1 acts as a bridge in 6 where the separation between the two Au(I) centers is 3.0402(5) Å. In the tetranuclear clusters 8 and 9, and in the cluster 10 analogous to 9 with 2 as bridging ligand, two orthogonal Co–Co edges are bridged by a diphosphine ligand and each cobalt center is thus coordinated by one P donor. Complex 3 was shown to react with the Pd(0) complex [Pd(dba)₂] (dba = dibenzylideneacetone) to afford a tetranuclear complex resulting from both the insertion of Pd(0) into the ligand C–Br bond and Pd(II)/Pd(0) comproportionation to form a doubly ligand-bridged Pd(I)–Pd(I) core.     

Structure of binuclear platinum(III) acetamidate complexes in solutions as probed by <Superscript>195</Superscript>Pt, <Superscript>13</Superscript>C,and <Superscript>1</Superscript>H NMR spectroscopy

¹⁹⁵Pt, ¹H, and ¹³C NMR spectroscopy was used to study the structure of binuclear platinum(III) acetamidate complexes with 1,10-phenanthroline and 2,2′-bipyridine ligands [Pt₂(phen)₂(acam)₄](NO₃)₂ (1) and [Pt₂(bipy)₂(acam)₄](NO₃)₂ (2) in aqueous solutions. The ¹⁹⁵Pt NMR spectra of solutions of complexes 1 and 2 in D₂O exhibit two signals with satellites due to the ¹⁹⁵Pt–¹⁹⁵Pt spin-spin coupling (¹ J(Pt–Pt) ≈ 6345 Hz), whereas their ¹H and ¹³C NMR spectra contain four sets of signals for the protons and the carbon atoms of the heterocyclic and acetamidate ligands. The signals were assigned using the COSY, NOESY, and HSQC/ HMBC experiments and comparing the coordination shifts of the signals for the protons of heterocycles. These data allowed us to draw a conclusion that binuclear complexes 1 and 2 in solution have a head-to-head structure with nonequivalent platinum(III) atoms (coordination cores PtN₅ and PtN₃O₂), the axial-equatorial coordination of the bidentate heterocyclic molecules, and two bridging and two terminal acetamidate ligands.     

Tuning the regioselectivity of (benzimidazolylmethyl)amine palladium(II) complexes in the methoxycarbonylation of hexenes and octenes

Reactions of N-(1H-benzoimidazol-2-ylmethyl-2-methoxy)aniline (L1) and N-(1H-benzoimidazol-2-ylmethyl-2-bromo)aniline (L2) with p-TsOH, Pd(AOc)₂ and two equivalents of PPh₃ or PCy₃ produced the corresponding palladium complexes, [Pd(L1)(OTs)(PPh₃)] (1), [Pd(L2)(OTs)(PPh₃)] (2) and [Pd(L1)(OTs)(PCy₃)] (3), respectively, in good yields. The new palladium complexes 1–3 and the previously reported complexes [Pd(L1)ClMe] (4) and [Pd(L2)ClMe] (5) gave active catalysts in the methoxycarbonylation of terminal and internal olefins to produce branched and linear esters. The effects of complex structure, nature of phosphine derivative, acid promoter and alkene substrate on the catalytic activities and selectivity have been studied and are herein reported.     

Cation-induced aggregation of sandwich lutetium(III) and Yb(III) complexes with tetra(15-crown-5)-substituted phthalocyanine as probed by <Superscript>1</Superscript>H NMR

The cation-induced aggregation of sandwich crown-substituted complexes [Ln(R₄Pc)₂] (Ln = Lu (I) and Yb (II), R₄Pc^2? is the 4,5,4′,5′,4″,5″,4?,5?-tetrakis(1,4,7,10,13-pentaoxatridecamethylene)phthalocyaninate ion) and Ln₂(R₄Pc)₃(Ln = Lu (III) and Yb (IV) in a CDCl₃-DMSO-d ₆ solution has been studied by ¹H NMR. The data obtained are consistent with the conclusions concerning the composition of supramolecular aggregates drawn from spectrophotometric titration data. The molecules of double-decker complexes I and II form supramolecular oligomers, whereas triple-decker complexes III and IV form supramolecular dimers, which is presumably due to the stronger distortion of the planes of the outer decks of the triple-decker complexes as compared to their double-decker analogues.     

Tris(5-bromo-2-methoxyphenyl)bismuth dicarboxylates [(C<Subscript>6</Subscript>H<Subscript>3</Subscript>(Br-5)(MeO-2)]<Subscript>3</Subscript>Bi[OC(O)CHal<Subscript>3</Subscript>]<Subscript>2</Subscript> (Hal = F,Cl): synthesis and structure

Tris(5-bromo-2-methoxyphenyl)bismuth dicarboxylates [(C₆H₃(Br-5)(MeO-2)]₃Bi[OC(O)CHal₃]₂, Hal = F (II) and Cl (III), have been synthesized by the reaction between tris(5-bromo-2-methoxyphenyl)bismuth (I) and trifluoroacetic acid and thrichloroacetic acid, respectively, in the presence of hydrogen peroxide in ether. According to X-ray diffraction data, a crystal of complex I contains two types of crystallographically independent molecules (a and b) both with a trigonal pyramid configuration. The bismuth atoms in complexes II and III have a distorted trigonal bipyramidal coordination with carboxylate substituents in axial positions. Axial OBiO angles are 166.3(3)° (II) and 171.6(2)° (III); equatorial CBiC angles are 118.0(3)°–123.1(3)° (II) and 113.6(3)°–127.4(3)° (III). Bi–C bond lengths are 2.189(7)–2.200(8) Å (II) and 2.190(8)–2.219(7) Å (III), and Bi–О distances are 2.280(6), 2.459(16) Å (II) and 2.264(5), 2.266(5) Å (III). Intramolecular contacts between the central atom and the oxygen atoms of carbonyl groups (Bi···O 3.028(9), 3.162(9) Å (II); 3.117(9), 3.202(9) Å (III)) are observed at maximum equatorial angles. The oxygen atoms of methoxy groups are coordinated to the bismuth atom. The Bi···O distances in complexes II and III (3.028(16), 3.157(16), 3.162(16) and 3.17(16), 3.143(16), 3.202(16) Å, respectively) are slightly longer than in complex I (3.007(9)–3.136(4) Å).     

Four supramolecular transition metal(II) complexes based on triazole-benzoic acid derivatives: crystal structure,Hirshfeld surface analysis,and spectroscopic and thermal properties

Four new complexes [M(3-tba)₂(H₂O)₄] (1–3) and [Co(4-tba)₂(H₂O)₄] (4) {M = Zn (1), Ni (2), Co (3), 3-Htba = 3-(1H-1,2,4-triazol-1-yl)benzoic acid, 4-Htba = 4-(1H-1,2,4-triazol-1-yl)benzoic acid} have been synthesized under solvothermal conditions and structurally characterized by single crystal X-ray diffraction. Complexes 1–4 are also determined by elemental analysis, X-ray powder diffraction, IR and electronic spectroscopy. Single crystal X-ray diffraction reveals that complexes 1–3 are isostructural and they crystallize in the orthorhombic space group of Pbca, while complex 4 belongs to triclinic system with Pī space group. Based on different intermolecular hydrogen bonding and π···π stacking interactions, complexes 1–4 further assembled into 3D supramolecular frameworks. Hirshfeld surface analysis was used to further study the intermolecular interactions of the complexes. The thermogravimetric analyses (TGA) reveal that these complexes possess good thermal stability, and the differential scanning calorimetry (DSC) analyses show intense exothermic phenomena in the decomposition processes of triazole groups. Besides, the photoluminescence property of complex 1 in the solid state is also determined.     

Microwave-assisted synthesis,crystal structures,and in vitro antibacterial studies of zinc(II) and nickel(II) complexes with Schiff bases

The syntheses of a mononuclear zinc(II) complex [ZnCl(L¹)(Amp)] (I) and a mononuclear nickel(II) complex [Ni(L²)(HL²)](BF₄) · 0.5H₂O (II) (HL¹ = 4-methyl-2-[(4-methylpyridin-2-ylimino) methyl]phenol, HL² = 4-methyl-2-[(pyridin-2-ylmethylimino)methyl]phenol; Amp = 2-amino-4- methylpyridine) were prepared under microwave irradiation. The complexes were characterized by a combination of elemental analyses, and IR and electronic spectra. Their structures were further confirmed by single crystal X-ray crystallography (СIF files CCDC nos 1437737 (I), 1437738 (II)). The Zn atom in the monomeric complex I is in tetrahedral coordination. The Ni atoms in the dimeric complex II are in octahedral coordination. Crystals of the complexes are stabilized by hydrogen bonds. In order to evaluate the biological activity of the complexes, in vitro antibacterial against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa was assayed. The complexes have strong activity against Bacillus subtilis.     

2-Morpholinoethyl-substituted <Emphasis Type="Italic">N</Emphasis>-heterocyclic carbene (NHC) precursors and their silver(I)NHC complexes: synthesis,crystal structure and in vitro anticancer properties

In this study, a series of unsymmetrically 2-morpholinoethyl-substituted benzimidazolium salts and their Ag(I)NHC complexes were synthesized. The 1,3-dialkylbenzimidazolium salts (1a–d) were synthesized in dimethylformamide at 80 °C temperature from the N-(2-morpholinoethyl)benzimidazole and alkyl halides. The Ag(I)NHC complexes (2a–d) were synthesized in dichloromethane at room temperature from the benzimidazolium salts and Ag₂O. All compounds were characterized by spectroscopic techniques (NMR and FT-IR) and elemental analyses. Also, the salt 1c and complex 2c were characterized by single-crystal X-ray crystallography. Anticancer activities of 2-morpholinoethyl-substituted benzimidazolium salts and Ag(I)NHC complexes were investigated against the MCF-7 breast cancer cell line, and the IC₃₀ and IC₅₀ values of these compounds were found to be in the range of 241–490 and 6–14 µM, respectively.     

Copper(I) complexes of 2-(benzen-1-yl)methyleneamino-3-aminomaleonitrile and triphenylphosphine ligands: synthesis,characterization, luminescence and catalytic properties

Some mixed ligand copper(I) complexes of general formula [Cu(L)(PPh₃)₃]X (X = Cl (1), ClO₄ (2), BF₄ (3) or PF₆ (4); L = 2-(benzen-1-yl)methyleneamino-3-aminomaleonitrile) were prepared and characterized by physicochemical and spectroscopic methods. A single-crystal X-ray diffraction study of [Cu(L)(PPh₃)₃]CIO₄ (2) revealed that the copper atom is four coordinated in a distorted tetrahedral geometry. Electrochemical studies of complexes 1–4 show quasireversible redox behavior corresponding to the Cu(I)/Cu(II) couple. Room temperature luminescence is observed for all four complexes. These complexes proved to be effective catalysts for the Sonogashira coupling of terminal alkynes with aryl halides at 90 °C.     

Dynamic in situ solvothermal reactions between ZnX<Subscript>2</Subscript> (X = Cl,ClO<Subscript>4</Subscript>) and a heterocyclic disulfide

Solvothermal reactions of 2-ppds (2-ppds = di[4-(pyridin-2-yl)pyrimidinyl]disulfide) with ZnX₂ (X = Cl, ClO₄) in mixed CH₃OH–CH₂Cl₂ solvent have been investigated. To better understand these reactions, solution analysis was conducted in parallel with single-crystal X-ray diffraction analysis of the in situ generated coordination complexes. At 120 °C, solvothermal reaction of 2-ppds with ZnCl₂ resulted in a discrete mononuclear coordination complex formulated as [ZnCl₂(L1)] (1), in which the zwitterion L1 (1-methyl-4-(pyridin-2-yl)pyrimidin-1-ium-2-olate) was formed in situ from 2-ppds, and solution analyses based on TLC and ESI–MS further showed that the reaction solution also contains in situ transformed products of L2 (bis(4-(pyridin-2-yl)pyrimidin-2-yl)sulfane) and L3 (2-methoxy-4-(pyridin-2-yl)pyrimidine). At 90 °C, solvothermal reaction between 2-ppds and Zn(ClO₄)₂ led to a discrete mononuclear coordination complex formulated as [Zn(SH)(L2)]ClO₄ (2) that features a terminally bound –SH group, while the reaction solution was also found to contain a library of in situ reaction products of 2-ppds including L1, L2, L3 and L4 ((4-(pyridin-2-yl)pyrimidin-2-yl) 4-(pyridin-2-yl)pyrimidine-2-sulfonothioate). Thus, the heterocyclic disulfide 2-ppds is transformed in situ into various organic products in a series of reactions involving C–S/S–S bond cleavage.     

Neutral and cationic (pyrazolylmethyl)pyridine palladium(II) complexes: kinetics and chemoselectivity studies in hydrogenation of alkenes and alkynes

Reactions of (3,5-dimethylpyrazolylmethyl)pyridine (L1) and (3,5-diphenylpyrazolylmethyl)pyridine (L2) with either [PdCl₂(NCMe)₂] or [PdClMe(COD)] afforded the respective neutral palladium complexes, [PdCl₂(L1)] (1), [PdCl₂(L2)] (2) and [PdClMe(L1)] (3). Treatment of complex 1 with equimolar amounts of PPh₃ or PPh₃/NaBAr₄ produced the corresponding cationic complexes [Pd(L1)ClPPh₃]Cl (4) and [Pd(L1)ClPPh₃]BAr₄ (5), respectively. Complexes 1–5 formed active catalysts in hydrogenation of alkenes and alkynes. Isomerization reactions were predominant in the hydrogenation reactions of terminal alkenes, while hydrogenation of alkynes involved a two-step process via alkene intermediates prior to the formation of the respective alkenes. The lack of induction periods in the hydrogenation reactions in addition to pseudo-first-order kinetics with respect to the substrates established the homogeneous nature of the active species.     

Addition of phenylacetylene and camphor to the complex [(dpp-bian)Eu(dme)<Subscript>2</Subscript>] (dpp-bian is the 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene dianion)

The reduction of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) with an excess of europium metal in 1,2-dimethoxyethane (dme) produces a divalent europium complex with the dpp-bian dianion, [(dpp-bian)Eu(dme)₂] (1). The reactions of 1 with phenyl-acetylene and camphor proceed via protonation of the diimine ligand to form the monomeric amido-amino complexes of divalent europium — [H(dpp-bian)Eu(C≡CPh)(dme)₂] (2) and [H(dpp-bian)Eu(camphor)(dme)₂] (3), respectively. Compounds 2 and 3 were characterized by IR spectroscopy and elemental analysis. Their molecular structures were determined by X-ray diffraction. Compounds 2 and 3 were shown to be monomeric seven-coordinate europium(ii) complexes with terminal phenylethynyl and enol ligands, respectively. According to the IR spectroscopic data, the terminal ligands in complexes 2 and 3 undergo tautomerization involving backward proton transfer from the amido-amino ligand to the substrate. The magnetic moment of compound 2 (8.03 μB) remains constant in the temperature range of 4—300 К and confirms the presence of divalent europium.