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.     

Ring-opening polymerization of ε-caprolactone catalysed by (pyridyl)benzoazole Zn(II) and Cu(II) complexes

This paper describes the synthesis of (pyridyl)benzoazole Zn(II) and Cu(II) complexes and their applications as catalysts in ring-opening polymerization (ROP) of ε-caprolactone (ε-CL). Reactions of 2-(3-pyridyl)-1H-benzimidazole (L1), 2-(2-pyridyl)-1H-benzothiazole (L2) and 2-(2-pyridyl)-1H-benzimidazole (L3) with Zn(II) and Cu(II) acetates produced the corresponding complexes; [Zn₂(L1)₂(OAc)₄)] (1), [Cu₂(L1)₂(OAc)₄] (2), [Zn(L2)(OAc)₂)] (3), [Zn(L3)(OAc)₂)] (4) and [Cu(L3), (OAc)₂)] (5). Molecular structures of complexes 2 and 5a revealed that while L1 adopts a monodentate binding mode, through the pyridyl nitrogen atom, L3 exhibits a bidentate coordination mode. All the complexes formed active catalysts in the ROP of ε-CL to afford moderate molecular weight polymers. The kinetics of the ROP reactions of ε-CL were pseudo-first-order with respect to monomer and catalysts.     

Palladacycles incorporating a carboxylate-functionalized phosphine ligand: syntheses,characterization and their catalytic applications toward Suzuki couplings in water

A series of acetato-bridged [C^X]-type (C = aryl carbanion, X = N, P) palladacycles (1–5) of the general formula [Pd(μ-CH₃COO)(C^X)]₂ were synthesized as metal precursors via slightly modified procedures. However, in the case of complex 5 with Dpbp (Dpbp = 2′-(diphenylphosphino-κP)[1,1′-biphenyl]-2-yl-κC) as the supporting C^P ligand, an unexpected dinuclear complex [Pd(μ-CO₂)(Dpbp)]₂ (6) was obtained as a by-product and structurally determined by X-ray crystallography. The reactions of complexes 1–4 with 2-(diphenylphosphino)benzoic acid conveniently afforded four carboxylate-functionalized phosphine complexes [Pd(C^N)(Dpb)] (Dbp = 2-(diphenylphosphino-κP)benzoato-κO, 7–10), two of which (9/10) are newly synthesized in the present work and have been fully characterized. A comparative catalytic study revealed that complex [Pd(Ppy)(Dpb)] (7) (Ppy = 2-(2-pyridinyl-κN)phenyl-κC) is the best performer in Suzuki cross-couplings in H₂O. In addition, complex 7 exhibits much better catalytic activity compared to the non-functionalized phosphine equivalent [Pd(OAc)(PPh₃)(Ppy)] (11), which clearly indicates the superiority of incorporating a carboxylate-functionalized phosphine ligand into the palladacycles. A preliminary mechanistic study uncovered a different precatalyst initiation pathway compared to other known analogues of catalyst precursors.     

Oxorhenium(V) complexes with bidentate carbohydrazide Schiff bases: synthesis,characterization and DNA interaction studies

The respective coordination reactions of trans-[ReOCl₃(PPh₃)₂] with N-[(4-oxo-4H-chromen-3-yl)methylidene]thiophene-2-carbohydrazide (Hchrtc) and N-[1,3-benzothiazol-2-ylmethylidene]thiophene-2-carbohydrazide (Hbztc) afforded two novel oxorhenium(V) complexes, cis-[ReOCl₂(chrtc)(PPh₃)] (1) and cis-[ReOCl₂(bztc)(PPh₃)] (2). These metal compounds were elucidated spectroscopically and their solid-state structures determined by single-crystal X-ray diffraction. The redox properties of the metal complexes were probed using cyclic and square wave voltammetry. The DNA interaction capabilities of 1 and 2 were gauged via UV/Vis spectroscopy DNA titrations and gel electrophoresis studies. A correlation is identified between the DNA cleavage observations and the redox potentials of the metal 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.     

Versatility and reactivity of salicylaldehyde <Emphasis Type="Italic">S</Emphasis>-methylisothiosemicarbazone in palladium(II) complexes

New palladium(II) complexes, [Pd(HL)Cl] · H₂O (I) and {K[Pd(L¹)(NO₂)] · H₂O}₂, with S-methylisothiosemicarbazone of salicylaldehyde (H₂L) and its derivative (H₂L¹) were synthesized. X-ray diffraction analysis demonstrated the ambident nature of S-alkylated thiosemicarbazone, which is attached to palladium(II) through O, N, and S donor atoms in I and through O, N, and N atoms in II. This is the first known case of metal coordination of the alkylated sulfur atom of a thiosemicarbazide moiety of the ligand. A mechanism of nitrosation of the terminal amide nitrogen atom of the H₂L¹ ligand during complexation was proposed.     

Coordination polymers of silver(I) with ditopic cross-conjugated dienone

The reaction of the silver salts AgX (a: X = BF₄^-, b: X = ClO₄^-, c: X = OTf^–) with α,α'-di(3/4-pyridylmethylene)cycloalkanones (L¹–L³) and piperidones (L⁴–L⁷) results in the formation of coordination products of general composition [AgX(L ⁿ )(solvent)] and [AgX(L ⁿ )] (L ⁿ = L¹–L⁷). All complexes were characterized by elemental analysis and IR-spectroscopy. The structures of [Ag(ClO₄)(L¹)(MeC≡N)]_∞ (1b · MeC≡N) and [Ag(ClO₄)(L¹)]_∞ (1b) in the solid state are reported. In both structures {Ag(L¹)}⁺ building units are linked to each other via Ag–N_pyridine primary bonds resulting in the formation of infinite chains. In both structures the ligands L¹ are fixed in transoid conformations, thus forming zig-zag polar chains. The structure of 1b · MeC≡N consists of pairs of tightly and loosely stacked chains. The tightly packed chains are weakly coupled by perchlorate anions acting as μ-bridges in between Ag(I) centers as well as by π–π-stacking interactions of unsaturated fragments of the respective ligands. In contrast, polar 2D layers composed of {Ag(L¹)} _m ^m+ chains, which interdigitate via multiple weak interactions by Ag–O contacts, are found in the solid structure of 1b. The dissolution of coordination products in coordinating solvents like MeCN or DMSO leads to the decomposition of complexes due to formation of silver-solvent coordination compounds. The coordination products 1–5 are stable in solid state against exposure to the ambient light, whereas solutions of the compounds, especially in DMSO-d₆, appeared to be photochemically labile. As revealed by NMR spectroscopic studies, the organic components undergo trans-cis isomerization.     

Syntheses,characterization, and crystal structures of two dinuclear nickel(II) and copper(II) complexes with Schiff bases

The phenolic azide bridged dinuclear nickel(II) complex, [Ni₂(L¹)₂(N₃)(H₂O)(μ_1,1-N₃)] · EtOH (I), and the thiocyanate bridged dinuclear copper(II) complex, [Cu₂(L²)₂(μ_1,1-NCS)₂] (II), where L¹ and L² are the deprotonated forms of 2-mothoxy-6-[(2-piperidin-1-ylethylimino)methyl]phenol and 2,4-dichloro-6-[(2-methylaminoethylimino)methyl]phenol, respectively, were synthesized and characterized by elemental analysis, IR spectra, and single-crystal X-ray diffraction. The crystal of I is orthorhombic: space group Pbca, a = 12.172(1), b = 20.953(1), c = 29.779(2) Å, V = 7594.8(9) ų, Z = 8. The crystal of II is monoclinic: space group P2₁/n, a = 8.7615(11), b = 19.672(2), c = 16.568(2) Å, β = 99.449(2)°, V = 2816.9(6) ų, Z = 4. The Ni atoms in I are in octahedral coordinations, and the Cu atoms in II are in square-pyramidal coordinations.     

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.     

Synthesis,crystal structure,and antibacterial activity of oxovanadium(V) complexes derived from <Emphasis Type="Italic">N</Emphasis>'-[1-(5-fluoro-2-hydroxyphenyl)methylidene]nicotinohydrazide and <Emphasis Type="Italic">N</Emphasis>'-(5-fluoro-2-hydroxybenzylidene)-2-hydroxynaphthylhydrazide

Two new oxovanadium(V) complexes, [VOL¹(OCH₃)(CH₃OH)] (I) and [VOL²(OCH₃)] (II), where L¹ and L² are the di-anionic form of N'-[1-(5-fluoro-2-hydroxyphenyl)methylidene]nicotinohydrazide and N'-(5-fluoro-2-hydroxybenzylidene)-2-hydroxynaphthylhydrazide, respectively, have been synthesized and characterized by elemental analysis, FT-IR spectra, and single crystal X-ray determination (CIF files CCDC nos. 891852 (I), 891853 (II)). The crystal of I is monoclinic: space group P2₁/c, a = 8.061(1), b = 15.293(2), c = 13.471(2) Å, ß = 92.595(2)°, V = 1658.8(4) ų, Z = 4. The crystal of II is monoclinic: space group P2₁/n, a = 7.4454(9), b = 8.0833(9), c = 28.906(2) Å, ß = 92.644(2)°, V = 1737.8(3) ų, Z = 4. The V atom in I is in an octahedral coordination, and that in II is in a square-pyramidal coordination. The antibacterial activity of the compounds against various bacteria was assayed.     

Ruthenium complexes with lumazine derivatives: structural,electrochemical, computational and radical scavenging studies

In this research study, the formation and characterization of new ruthenium(II) and (III) complexes encompassing multidentate ligands derived from 6-acetyl-1,3,7-trimethyllumazine (almz) are reported. The 1:1 molar coordination reactions of trans-[RuCl₂(PPh₃)₃] with N-1-[1,3,7-trimethyllumazine]benzohydride (bzlmz) and 6-(N-methyloxime)-1,3,7-trimethyllumazine (ohlmz) formed a diamagnetic ruthenium(II) complex, cis-[RuCl₂(bzlmz)(PPh₃)] (1), and paramagnetic complex, cis-[Ru^IIICl₂(olmz)(PPh₃)] (2) [Holmz = 6-(N-hydroxy-N′-methylamino)-1,3,7-trimethyllumazine], respectively. These ruthenium complexes were characterized via physico-chemical and spectroscopic methods. Structural elucidations of the metal complexes were confirmed using single crystal X-ray analysis. The redox properties of the metal complexes were investigated via cyclic voltammetry. Electron spin resonance spectroscopy confirmed the presence of a paramagnetic metal centre in 2. The radical scavenging activities of the metal complexes were explored towards the DPPH and NO radicals. Quantum calculations at the density functional theory level provided insight into the interpretation of the IR and UV–Vis experimental spectra of 1.     

Syntheses and crystal structures of copper(II) and nickel(II) complexes derived from 2-bromo-4-chloro-6-[(2-methylaminoethylimino)methyl]phenol

A new centrosymmetric mononuclear copper(II) complex [Cu(L)₂](ClO₄)₂ (I) and a new centrosymmetric mononuclear nickel(II) complex [Ni(L)₂(MeOH)₂](ClO₄)₂ (II), where L is the zwitterionic ligand 2-bromo-4-chloro-6-[(2-methylammonioethylimino)methyl]phenolate, have been prepared from the Schiff base 2-bromo-4-chloro-6-[(2-methylaminoethylimino)methyl]phenol with copper perchlorate and nickel perchlorate, respectively. The complexes were characterized by elemental analysis, infrared spectra, and single-cyrstal X-ray diffraction (CIF files CCDC nos. 1408054 (I) and 1407973 (II)). Complex I crystallizes in the monoclinic space group P2₁/c with unit cell dimensions a = 7.7736(4), b = 21.608(1), c = 8.5194(4) Å, β = 93.907(2)°, V = 1427.7(1) ų, Z = 2, R ₁ = 0.0546, and wR ₂ = 0.1531. Complex II crystallizes in the monoclinic space group P2₁/c with unit cell dimensions a = 21.324(3), b = 16.821(2), c = 9.425(1) Å, β = 90.114(2)°, V = 3380.5(7) ų, Z = 4, R ₁ = 0.0693, and wR ₂ = 0.1627. The Cu atom in I is in square planar coordination, and the Ni atom in II is in octahedral coordination.     

Palladium clusters Pd<Subscript>4</Subscript>(SR)<Subscript>4</Subscript>(OAc)<Subscript>4</Subscript> and Pd<Subscript>6</Subscript>(SR)<Subscript>12</Subscript> (R = Bu,Ph): Structure and properties

The structures of the Pd₄(SBu)₄(OAc)₄ (I) and Pd₆ (SBu)₁₂ (II) palladium clusters are determined by the X-ray diffraction method. For cluster I: a = 8.650(2), b = 12.314(2), c = 17.659(4) Å, α = 78.03(3)°, β = 86.71(2)°, γ = 78.13(3)°, V = 1800.8(7) ų, ρcalcd = 1.878 g/cm³, space group P \(\bar 1\), Z = 4, N = 3403, R = 0.0468; for structure II: a = 10.748(2), b = 12.840(3), c = 15.233(3) Å, α = 65.31(3)°, β = 70.10(3)°, γ = 72.91(3)°, V = 1767.4(6) ų, ρ calcd = 1.605 g/cm³, space group P \(\bar 1\), Z = 1, N = 3498, R = 0.0729. In cluster I, four Pd atoms form a planar cycle. The neighboring Pd atoms are bound by two acetate or two mercaptide bridges (Pd…Pd 2.95–3.23 Å, Pd…Pd angles 87.15°–92.85°). In cluster II, the Pd atoms form a planar six-membered cycle with Pd···Pd distances of 3.09–3.14 Å, the PdPdPd angles being 118.95°–120.80°. The Pd atoms are linked in pairs by two mercaptide bridges. The formation of clusters I and II in solution is proved by IR spectroscopy and calorimetry. Analogous clusters are formed in solution upon the reaction of palladium(II) diacetate with thiophenol.     

New coordination modes of iminodiacetamide type ligands in palladium(II) complexes: crystallographic and DFT studies

The reactions of N-alkyliminodiacetamide derivatives, namely N-ethyliminodiacetamide (CH₃CH₂N(CH₂CONH₂)₂; Etimda) and N-isopropyliminodiacetamide (CH₃)₂CHN(CH₂CONH₂)₂; i-Primda), with sodium tetrachloropalladate(II) in aqueous solutions were investigated. Three new palladium(II) complexes, [Pd(Etimda_?H)₂]?2H₂O (1), [Pd(i-Primda_?H)₂]?2H₂O (2) and [PdCl₂(i-Primda)] (3), were obtained and characterized by X-ray structural analysis, infrared spectroscopy and thermal analysis (TGA). The square planar coordination environments around the palladium(II) ions in complexes 1 and 2 consist of two N,N′-bidentate N-alkyliminodiacetamidato ligands, with imino N atoms in trans-position. The complex 3 also exhibits a square planar coordination environment around Pd(II), but with two chloride ions and one neutral N-isopropyliminodiacetamide ligand bound in an N,O′-bidentate coordination mode. The described coordination modes, as well as the presence of deprotonated amide groups in ligands in 1 and 2, are found for the first time in palladium(II) complexes with iminodiacetamide type ligands. The molecular geometries and infrared spectra of these three complexes were also modelled using DFT calculations, at the BP86-D3/def2-TZVPP/PCM level of theory. The RMSD values suggest a good agreement of the calculated and experimental geometries. A QTAIM analysis suggests a qualitative correlation between bond lengths and energy densities, also supported by an NBO analysis. The dimer interaction energy between complex units was estimated at about ?15 kcal/mol for all complexes.     

Diverse topologies of three cobalt(II) coordination polymers constructed from flexible bis(benzimidazole) and dicarboxylate ligands

Three cobalt(II) coordination polymers {[Co(L1)(nda)(H₂O)₂]·2H₂O} _n (1), [Co(L2)(tbi)(H₂O)] _n (2) and [Co(L2)(bpdc)(H₂O)] _n (3) (L1 = 1,3-bis(5,6-dimethylbenzimidazol-1-yl)-2-propanol, L2 = 1,3-bis(benzimidazol-1-yl)-2-propanol, H₂nda = 2,6-naphthalenedicarboxylic acid, H₂tbi = 5-tert-butyl isophthalic acid and H₂bpdc = 4,4′-biphenyldicarboxylic acid) were synthesized and characterized by physicochemical and spectroscopic methods. Complex 1 exhibits a 1D loop-like structure, which is further extended into a 3D 3,3,4T31 network through two O–H···O hydrogen bonding interactions. Complex 2 displays a 1D ladder-like chain, arranged into a 2D supramolecular network with 3,3,4L34 topology via classical O–H···O hydrogen bonding interactions, whereas complex 3 features a 2D 3,4L13 layer structure and further assembles into a 3D framework with a twofold interpenetrating sqc65 topology through O–H···O hydrogen bonding interactions. The fluorescence and catalytic properties of these complexes for the degradation of Congo red in a Fenton-like process have been investigated.     

(P-Bis(pentafluorophenyl) substituted) PCP-pincer Ru(II) complexes: A theoretical study of the molecular structure and electronic properties

The differences between the molecular structures of the PCP-pincer complex [RuCl{C₆H₃(CH₂P(C₆H₅)₂)₂-2,6}(PPh₃)] ([RuCl(PCP^H)(PPh₃)], 1) and its tetrakis-pentafluorophenyl substituted analogue [RuCl{C₆H₃(CH₂P(C₆F₅)₂)₂-2,6}(PPh₃)] ([RuCl(PCP^F20)(PPh₃)], 2) have been rationalised by performing calculations on the cations [Ru(PCP^H)(PPh₃)]⁺ (1cat) and [Ru(PCP^F20)(PPh₃)]⁺ (2cat). The molecular interactions between the chloride ligand and the axial rings, as found in 1 and 2, respectively, have been studied computationally in the model systems [(C₆X₅PH₂)₂Cl⁻] (X = H, F). The calculations on 2cat show that in 2 it is most likely the attractive electrostatic interaction between the chloride ligand and the fluorinated phenyl rings that forces the C_ipso atom to occupy an axial position rather than an equatorial one in the observed (X-ray of 2) square pyramidal arrangement. In 1, however, repulsive steric hindrance forces the PPh₃ ligand to take the apical position. The applicability of the TD-DFT method for the calculation of the electronic spectra of the PCP-pincer compounds 1 and 2 has been tested. The results indicate that the excitation energies calculated for both complexes are in a reasonable agreement with the experimental absorption maxima. However, for 1, all the calculated transition energies are underestimated.     

Alternative preparation and characterization of platinum(II) organometallic dinuclear complexes and oligomers with 3,8-diethynylphenanthroline derivatives

Novel platinum(II) organometallic dinuclear complexes and oligomers with two types of phenanthroline ligands, namely 3,8-diethynylphenanthroline (L1) and 3,8-bis-(4-ethynyl-phenylethynyl)-1,10-phenanthroline (L2), were synthesized from trans-Pt(PBu₃)₂(1-ethynyl-4-methyl-benzene)Cl and trans-Pt(PBu₃)₂Cl₂ by transmetalation of copper ion. The alternative procedure targeted platinum oligomer termination selection of either chloride or respective phenanthrolines and was successfully performed with different purifications by extraction and column chromatography. The structural formulae of these platinum complexes and oligomers were revealed with by analysis of both ³¹P{¹H}-NMR and ¹H-NMR spectral data. Alternative preparations of platinum oligomers with two types between chloride and respective phenanthroline termination are very useful for the selective synthesis for hybrid polymers with the coupling reaction with two different platinum oligomers with different diethynylaryl ligands. The platinum organometallic compounds showed similar absorption bands in the UV–Vis region. Those prepared with L1 had a strong absorption band at around 400 nm, assignable to the lowest energy metal-perturbed ¹[π–π*] transitions, while in compounds prepared with L2, the strong band appeared around 410 nm, because L2 has an extended π conjugation relative to L1. No distinct differences were observed in the absorption spectra of these platinum oligomers between the different terminal structures, chloride or various phenanthrolines. The luminescence spectra of the platinum compounds prepared with either L1 or L2, however, showed a distinct difference. Those with L1 showed only a phosphorescence assignable to a typical metal-perturbed ³[π–π*] transition with vibronic progressions centered at around 530 nm in deoxygenated CH₂Cl₂ at room temperature, while those with L2 showed weak dual emissions assignable to a mixture of typical metal-perturbed ¹[π–π*] and ³[π–π*] transitions in the visible region.     

Synthesis characterization,crystal structures,and antibacterial activity of 8-hydroxyquinoline-coordinated oxidovanadium(V) complexes with tridentate hydrazone ligands

Two new oxidovanadium(V) complexes, [VO(L¹)(L)] (I) and [VO(L²)(L)] (II), where L¹ and L² are the dianionic form of N'-(2-hydroxy-5-methoxybenzylidene)pivalohydrazide (H₂L¹) and N'-(2-hydroxy-3-methoxybenzylidene)pivalohydrazide (H₂L²), respectively, and L is the monoanionic form of 8-hydroxyquinoline (HL), were prepared and characterized by elemental analysis, infrared and electronic spectra, and ¹H NMR spectra. Structures of the complexes were further confirmed by single crystal X-ray determination (CIF files CCDC nos. 1477854 (I), 1477856 (II)). H₂L¹ and H₂L² coordinate to the V atoms through the phenolate O, imino N, and enolate O atoms. 8-Hydroxyquinoline coordinates to the V atoms through bidentate ON donor set. The V atoms of the complexes are in octahedral coordination with the oxo group furnished the octahedral geometry. The complexes show effective antibacterial activity against Bacillus subtilis.     

Synthesis,crystal structures,and characterization of a new substituted 1,2,4-triazole and its two Co(II)/Mn(II) complexes

A new triazole-substituted ligand H₂L (H₂Trza = 3-amino-1H-1,2,4-triazole-5-acetate) and its two new isomorphic compounds [M(HTrza)₂(_H2O)₂] ? 2H₂O (Co(I) and Mn(II)) have been synthesized and characterized structurally. Their X-ray crystal structures (CIF files CCDC nos. 906893 for I and 906892 for II) show that H₂L belongs to a tetragonal system; space group P4₃ with a = b = 5.0445(13), c = 27.054(10) Å; Z = 4. Complex I belongs to a monoclinic system; space group P2₁/n with a = 7.6543(8), b = 7.3453(8), c = 13.6283(14) Å; β = 91.5990(10)°, Z = 2. Complex II belongs to a triclinic system; space group with a = 6.8550(15), b = 8.0630(18), c = 15.173(4) Å; α = 84.794(4)°, β = 79.005(3)°, γ = 73.779(4)°, Z = 2. X-ray analysis demonstrates that compound H₂L is found to contain a H₂Trza and a lattic water molecule; complexes I and II are discrete mononuclear species. The central Co(II) and Mn(II) atoms exhibit octahedral coordinations, type 4 + 2. In two compounds, the coordination entities are further organized via hydrogenbonding interactions to generate uniform supramolecular networks. Thermal stabilities of two compounds were examined by thermogravimetric analysis.     

Synthesis and X-ray investigation of Rb<Subscript>2</Subscript>[Pd(NO<Subscript>3</Subscript>)<Subscript>4</Subscript>] and Cs<Subscript>2</Subscript>[Pd(NO<Subscript>3</Subscript>)<Subscript>4</Subscript>]

Powder and single crystal X-ray diffraction studies have been performed for anhydrous nitrate complexes Rb₂[Pd(NO₃)₄] (I) and Cs₂[Pd(NO₃)₄] (II). Crystal data for I: a = 7.843(1) Å, b = 7.970(1) Å, c = 9.725(1) Å; β = 100.39(1)°, V = 597.9(1) Å ³, space group P2₁/c, Z = 2, d _calc = 2.918 g/cm³; for II: a = 10.309(2) Å, b = 10.426(2) Å, c = 11.839(2) Å; β = 108.17(3)°, V = 1209.0(4) ų, space group P2₁/c, Z = 4, d ^calc = 3.408 g/cm³. The structures are formed by isolated [Pd(NO₃)₄]^2? complex anions and alkali metal cations. The plane-square environment of the Pd atom is formed from the oxygen atoms of the monodentate nitrate groups. The geometrical characteristics of the complex anions are analyzed. Compound II has a short contact Pd...Cs 3.252 Å.