Theoretical study on the singlet and triplet potential energy surfaces of NH (X3Σ−) + HCNO reaction

Both the singlet and triplet potential energy surfaces (PESs) of the NH (X³Σ^?) + HCNO reaction have been investigated at the BMC-CCSD level based on the UB3LYP/6-311++G(d, p) structures. The results show that the title reaction is more favorable through the singlet potential energy surface than the triplet one. For the singlet potential energy surface of the NH (X³Σ^?) + HCNO reaction, the most feasible association of NH (X³Σ^?) with HCNO is found to be a non-barrier nitrogen-to-carbon attack forming the adduct a (trans-HNCHNO), which can isomerize to the adduct b (cis-HNCHNO). The most feasible channel is that the 1, 3-H shift with N2–H2 and C–N1 bonds cleavage associated with the N1–H2 bond formation of adduct a leads to the product P ₁ (HCN + HNO). Moreover, P ₂ (HNC + HNO) should be the competitive product. The other products, including P ₃ (NH₂ + NCO) and P ₄ (N₂H₂ + CO), are minor products. The product P ₁ can be obtained through two competitive channels Path 1: R → a → P ₁ and Path 3: R → b → d → P ₁ , whereas the product P ₂ can be formed through Path 2: R → b → d → P ₂ . At high temperatures, the nitrogen-to-nitrogen approach may become feasible. For the triplet potential energy surface of the NH (X³Σ^?) + HCNO reaction, the Path 10: R → ³ a → ³ a ₁ → P ₁ should be the most feasible pathway due to the less reaction steps and lower barriers. These conclusions will have impacts on further experimental investigations.     

Theoretical study on the mechanism of C2Cl3 + NO2 reaction

The radical-molecule reaction of C₂Cl₃ with NO₂ is explored at the B3LYP/6-311G(d,p) and CCSD(T)/6-311+G(d,p) (single-point) levels. On the singlet potential energy surface (PES), the association between C₂Cl₃ and NO₂ is found to be carbon-to-nitrogen attack forming the adduct C₂Cl₃NO₂ (1) without any encounter barrier, followed by isomerization to C₂Cl₃ONO (2). Starting from 2, the most feasible pathway is the N–O1 bond cleavage which lead to P ₁ (C₂Cl₃O + NO). Much less competitively, 2 transforms to the three-membered ring isomer c-OCCl₂C–ClNO (4 ^a ) which can easily interconvert to c-OCCl₂C–ClNO 4 ^b . Then 4 (4 ^a , 4 ^b ) takes direct C1–C2 and C2–O1 bonds cleavage to give P ₂ (COCl₂ + ClCNO). The lesser competitive channel is the 4 ^a isomerizes to the four-membered ring intermediate O-c-CNClOCCl₂ (5) followed by dissociation to P₃ (CO + ClNOCCl₂). The concerted 1,2-Cl shift along with C1–O1 bond rupture of 4 ^b to form ONC(O)CCl₃ (6) followed by dissociation to P ₄ (ClNO + OCCCl₂) is even much less feasible. Moreover, some of P ₃ and P ₄ can further dissociate to P ₅ (ClNO + CO + CCl₂). Compared with the singlet pathways, the triplet pathways may have less contribution to the title reaction. Our results are in marked difference from previous theoretical studies which showed that two initial adducts C₂Cl₃–NO₂ and C₂Cl₃–ONO are obtained. Moreover, in the present paper we focus our main attentions on the cyclic isomers in view of only the chain-like isomers are considered by previous studies. The present study may be helpful for understanding the halogenated vinyl chemistry.     

Mononuclear copper(II) complexes of bis-triazole-based macrocyclic Schiff base hydrazones: direct synthesis,EPR studies,magnetic and thermal properties

Mononuclear copper(II) complexes of 1,2,4-triazole-based Schiff base macrocyclic hydrazones, III and IV, have been reported. The prepared amorphous complexes have been characterized by spectroscopic methods, electron spray ionization mass spectrometry, and elemental analysis data. Electrochemical studies of the complexes in DMSO show only one quasi-reversible reduction wave at +0.43 V (ΔE = 70 mV) and +0.42 V (ΔE = 310 mV) for III and IV, respectively, which is assigned to the Cu(II) → Cu(I) reduction process. Temperature dependence of magnetic susceptibilities of III and IV has been measured within an interval of 2–290 K. The values of χ_M at 290 K are 1.72 × 10^?3 cm³ mol^?1 and 1.71 × 10^?3 for III and IV, respectively, which increases continuously upon cooling to 2 K. EPR spectra of III and IV in frozen DMSO and DMF were also reported. The trend g_|| > g⊥ > g_e suggests the presence of an unpaired electron in the d_x2?y2 orbital of the Cu(II) in both complexes. Furthermore, spectral and antimicrobial properties of the prepared complexes were also investigated.     

Radical reaction HCNO + 3NH: a mechanistic study

The complex triplet potential energy surface for the reaction of HCNO with NH is investigated at the G3B3 level using the B3LYP/6-311++G(d,p), and QCISD/6-311++G(d,p) geometries. Various possible isomerization and dissociation pathways are probed. The initial association between HCNO and NH is found to be carbon to nitrogen attack leading to HNCHNO 2a, which can convert to 2b, 2c, and 2d. Subsequently, 1,4-H-shift of 2a to form NCHNOH 3a followed by dissociation to P ₂ (¹HCN + ³HON) is the most feasible pathway. Much less competitively, 2d undergoes successive 1,3-H-shift and C-N cleavage to form HNCNOH 8b, and then to product P ₃ (¹HNC + ³HON), the second feasible pathway. 8b can alternatively isomerize to 8c followed by N–O bond rupture to generate P ₆ (²OH + ²HNCN), the lesser followed feasible pathway. In addition, 2b takes continuously 1,3- and 1,2-H-shift to form NC(H)NHO 6a, then to ONHCNH 7a which can convert to 7b. Eventually, 7b may take C-N bond fission to produce P ₅ (¹HNC + ³HNO), the least feasible pathway. The present paper may be helpful for future experimental identification of the product distributions for the title reaction, and may be helpful to deeply understand the mechanism of the title reaction.     

Synthesis and structural characterization of binuclear ytterbium(III) complexes with 2-amino and 3-amino benzoic acid

Two novel homobinuclear ytterbium(III) complexes, [Yb₂(2AMB)₆(H₂O)₄] · 2C₂H₆O (I) and Yb₂(3AMB)₆(H₂O)₄] · 3H₂O (II) (2AMB = 2-aminobenzoic acid, 3AMB = 3-aminobenzoic acid) have been synthesized and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis and X-ray crystallography (CIF files CCDC nos. 950103 (I), 921652 (II)). Complex I crystallizes in triclinic space group \(P\bar 1\) and complex II crystallizes in monoclinic space group P2₁/n. X-ray analysis shows that both complexes (I, II) have the dinuclear structure. The central Yb³⁺ ions in both complexes are eight-coordinated adopting distorted YbO₈ dodecahedral geometry. Each Yb³⁺ ion is coordinated to two O atoms from bridging carboxylate, four O atoms from the chelating carboxylate ligands and two O atoms of water molecules. The crystal structure of I and II are stabilized by N-H…O, O-H…O, O-H…N, and C-H…O hydrogen bonds, C-H…π interactions and weak π-π stacking interactions.     

Syntheses and crystal structures of (18-crown-6)bis(perchlorato-O,O′)strontium and (18-crown-6)bis(perchlorato-O,O′)barium

Two complexes, namely, (18-crown-6)bis(perchlorato-O,O′)strontium (I) and (18-crown-6)bis(perchlorato-O,O′)barium (II), are synthesized. Their crystal structures are determined by X-ray diffraction analysis. The structures of I (space group P2₁/c, a = 15.266 Å, b = 11.080 Å, c = 13.235 Å, β = 109.20°, Z = 4) and II (space group P2₁/n, a = 8.330 Å, b = 11.202 Å, c = 11.752 Å, β = 98.38°, Z = 2) are solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.077 (I) and 0.041 (II) against 3714 (I) and 2478 (II) independent reflections (CAD-4 diffractometer, λMoK _α radiation). Complex molecules [Sr(18C6)(ClO₄)₂] in the structure of I and [Ba(18C6)(ClO₄)₂] in II (in the inversion center)—are of the host-guest type. The Sr²⁺ or Ba²⁺ cation is localized in the center of a cavity of the 18-crown-6 ligand and coordinated by its all six O atoms. In compounds I and II, the coordination polyhedron of the Sr²⁺ and Ba²⁺ cations (coordination number 10) can be described as a distorted hexagonal bipyramid with two bifurcated vertices at two O atoms of two ClO ₄ ^? ligands, which are disordered in I and II and each of them has two orientations.     

Synthesis,characterization, and thermal behavior of palladium(II) complexes containing 4-iodopyrazole

The mononuclear pyrazolyl complexes [PdCl₂(HIPz)₂] (1), [PdBr₂(HIPz)₂] (2), [PdI₂(HIPz)₂] (3), [Pd(SCN)₂(HIPz)₂] (4), and [Pd(NHCOIPz)₂] (5) have been prepared. Compound 1 was obtained from the displacement of acetonitrile from [PdCl₂(CH₃CN)₂] precursor by the 4-iodopyrazole (HIPz) ligand, whereas 2–5 were synthesized by substitution of the chlorido in 1 by the respective anionic group. The compounds were characterized by elemental analysis, infrared spectroscopy, and ¹H NMR spectroscopy. The thermal behavior of 1–5 has been studied by TG and DTA. The thermal stability of [PdX₂(HIPz)₂] compounds varies according to the trends X = Cl^? < I^? ? SCN^?< Br^?. No stable intermediates were isolated during the thermal decompositions due to the overlap of the degradation processes. The final products of the thermal decompositions were characterized as metallic palladium by X-ray powder diffraction.     

Naphthologs of overcrowded bistricyclic aromatic enes: (E)-bisbenzo[a]fluorenylidene

(E)-11H-Bisbenzo[a]fluorenylidene (E-6) was synthesized by Barton’s double extrusion diazo-thione coupling method from 11H-benzo[a]fluoren-11-thione (11) and 11-diazo-11H-benzo[a]fluorene (13). The reaction is probably thermodynamically controlled; in the event that the less stable Z -6 is also formed, it would rapidly undergo Z → E diastereomerization to give E -6. The B3LYP/6-311G(d,p) calculated diastereomerization barrier for Z -6 → E -6 is ΔG ₂₉₈ = 57.0 kJ/mol (13.6 kcal/mol). The calculated equilibrium constant K _eq(E -6 → Z -6) = 92:8 (at 298 K) is indicative of a marked diastereoselectivity of the reaction leading to E -6. The structure of E-6 was established by ¹H-NMR and ¹³C-NMR spectroscopies and by X-ray analysis. PAE E-6 crystallizes in the monoclinic space group C2/c. The unit cell of the crystal structure E -6 contains eight molecules, arranged as four pairs of enantiomers. PAE E -6 adopts a twisted conformation with the pure twist of the central C¹¹=C^11′ bond ω = 39°. The dihedral angle ν in E -6 is 60.6°, which is significantly higher than the respective dihedral angle in PAEs Z -6, 2, E -7, Z -7, 14, and 15. The large syn-pyramidalization angles at C¹¹ and C^11′ (χ = 12.6° and 14.8°) of E-6 indicates the enhanced strain in the fjord regions of the molecule. The enhanced twist is primarily attributed to the double benzo[a]annelation of the bifluorenylidene moiety at the fjord regions. The B3LYP/6-311G(d,p) calculated structure of E -6 is in a very good agreement with the experimental X-ray structure. PAE E -6 adopts a twisted conformation in solution, with the downfield chemical shift of H¹/H^1′ (8.31 ppm); H¹⁰/H^10′ (δ = 7.20 ppm) and H⁹/H^9′ (δ = 6.86 ppm) in E -6 are positioned above the planes of the opposing naphthalene rings. PAEs E -6 and Z -6 are significantly higher in energy than their corresponding benzo[b]annelated isomers E -7 and Z -7.     

Complexation of the cesium cation with 1,3-alternate-25,27-bis(1-octyloxy)calix[4]arene-crown-6

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Cs⁺(aq) + I^?(aq) + 1(nb) ? 1·Cs⁺(nb) + I^?(nb) taking place in the two–phase water–nitrobenzene system (1 = 1,3-alternate-25,27-bis(1-octyloxy)calix[4]arene-crown-6; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K _ex (1·Cs⁺, I^?) = 2.9 ± 0.1. Further, the stability constant of the 1·Cs⁺ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log β_nb (1·Cs⁺) = 8.8 ± 0.1. Finally, by using quantum–mechanical DFT calculations, the most probable structure of the resulting cationic complex species 1·Cs⁺ was derived.     

Complexes built with a scorpion-type tripodal ligand and metal ions: syntheses, structural features, electrochemical properties and magnetic properties

The complexes [Fe(bpz*mpy)₂](ClO₄)₂ (1a), [Cu(bpz*mpy)₂](ClO₄)₂ (1b) and [Ag(bpz*mpy)(Ph₃P)](ClO₄) · H₂O (2) (bpz*mpy = pyridin-2-yl-bis(3,5-dimethylpyrazol-1-yl)methane) have been synthesized and characterized by physicochemical and spectroscopic methods. X-ray crystallographic analysis reveals that the central Fe^II and Cu^II ions in complexes 1a and 1b are located on a twofold rotation axis and have a distorted octahedral coordination sphere, while the Ag^I center in complex 2 is tetrahedrally coordinated. The electrochemical properties of complex 1b have been investigated. Furthermore, a variable temperature magnetic susceptibility study of complex 1a has also been performed over the measured temperature range 2–300 K.     

How do phosphoramides compete with phosphine oxides in lanthanide complexation? Structural, electronic and energy aspects at ab initio and DFT levels

Novel comparison of the structural, electronic and energy aspects of lanthanide complexes of model phosphoramides (PAs) with those of phosphine oxides (POs), phosphate esters (PEs) and phosphoryl trihalides (PHs) has been carried out by ab initio and DFT calculations. Atoms in Molecules (AIM) and Natural Bonding Orbital (NBO) analyses were performed to understand the electronic structure of ligands L and related complexes, L–Ln³⁺. NBO analysis indicates that the negative charge on phosphoryl oxygen (O_P) and the p character of the phosphoryl lone pair, Lp(O_P), increase in the order PH < PE < PO < PA. Positive charge of the lanthanide cation in PA complexes is less than those of PH, PE and PO complexes, due to the more intense ligand to metal charge transfer (LMCT). The metal–ligand distance decreases in the order PH > PE > PO > PA, which is confirmed by the results of AIM analysis. Charge density at the bond critical point of L–Ln³⁺ follows the sequence PH < PE < PO < PA. The results of the Energy Decomposition Analysis (EDA) indicate that the donative interaction and LMCT increases in order PH < PO < PE < PA. The effect of basis set superposition error (BSSE) on the L···Ln³⁺ interaction energies was also studied in detail at DFT, MP2 and CCSD(T) levels using the counterpoise (CP) method. Trends in the CP-corrected L–Ln³⁺ bond energies are in good accordance with the optimized O_P···Ln³⁺ distances. The results show that the difference between CP-corrected and uncorrected interaction energies in PA complexes is larger than those in the others, because PAs are more deformable. It is depicted that PAs are comparable with POs in lanthanide complexation.     

Synthesis and structure of antimony iodide complexes: [Ph3MeP] + 2 [SbI5]2−, [Ph3MeP] + 3 [Sb3I12]3−·Me2C=O, [Ph3MeP] + 3 [Sb3I12]3−, and [Ph3MeP] + 3 [Sb2I9]3−

Complexes with antimony-containing anions, [Ph₃MeP] ₊ ² [SbI₅]^2? (I), [Ph₃MeP] ₊ ² [Sb₃I₁₂]^3? (II), [Ph₃MeP] ₊ ³ [Sb₃I₁₂]^3? · Me₂C=O (III), and [Ph₃MeP] ₊ ³ [Sb₂I₉]^3? (IV), were synthesized by reacting triphenylmethylphosphonium iodide with antimony iodide. The central atom in the cations of the complexes has a distorted tetrahedral coordination. In the trinuclear anions of complexes II and III, each of the terminal SbI₃ groups is bound to the central Sb atom through two μ₂- and one μ₃ iodine bridges (SbSbSb angles are 103.0° and 102.2°, respectively). In the binuclear anion of complex IV, antimony atoms are linked with each other via three bridging iodine atoms.     

Synthesis and characterization of glycol ether and oxime modified precursors of niobium(V) for soft transformation to niobia

A glycol ether modified precursor, [Nb{O(CH₂CH₂O)₂}(OPrⁱ)₃] (A) was prepared by the reaction of Nb(OPrⁱ)₅ with O(CH₂CH₂OH)₂ in 1:1 molar ratio in anhydrous benzene. Further reactions of A with a variety of internally functionalized oximes in different molar ratios, yielded heteroleptic complexes of the type, [Nb{O(CH₂CH₂O)₂}(OPrⁱ)_3?n{ON = C(CH₃)(Ar)}_n] (1–9) {where Ar = C₄H₃O-2, n = 1 [1], n = 2 [2], n = 3 [3]; C₄H₃S-2, n = 1 [4], n = 2 [5], n = 3 [6]; C₅H₄N-2, n = 1 [7], n = 2 [8], n = 3 [9]}. All the above derivatives have been characterized by elemental analyses, FT-IR, NMR (¹H, ¹³C {¹H}) and FAB mass studies. Spectral studies of 1–9 suggest the presence of mono- and bi-dentate mode of oxime moieties, in the solution and in the solid states, respectively. FAB mass studies indicate monomeric nature for 3 and dimeric nature for A. TG curves of A and 6 show their low thermal stability. Soft transformation of A and 3 to pure niobia, a and b, respectively have been carried out by sol–gel technique. The XRD patterns of niobia a and b suggest the formation of nano-size crystallites of average size of 10.8 and 19.5 nm, respectively. The XRD patterns also indicate the formation of monoclinic phase of the niobia in both the cases. Absorption spectra of a and b suggest energy band gaps of 4.95 and 4.39 eV, respectively.     

Solubilization of cholesterol in aqueous solution by two β-cyclodextrin dimers and a negatively charged β-cyclodextrin derivative

Two βCD dimers (linked by succinic acid, 2, or ethylenediaminetetraacetic acid, EDTA, 3, bridges) and a negatively charged monomer derivative of βCD, 1, have been synthesized and their ability to solubilize cholesterol in aqueous solution was studied. The three compounds exhibit a great capacity in solubilizing cholesterol as, for instance, concentrations up to 6 mM of cholesterol were measured in the presence of 25 mM of 3. The phase-solubility diagrams of the two dimers exhibit A _L type profiles while the monomer 1 follows an A _P isotherm. The cholesterol/dimer complexes have 1:1 stoicheiometries while monomer 1 forms two complexes with molar ratios of 1:1 and 1:2 (cholesterol/1). The equilibrium constants are K _1:1 = (5.9 ± 0.3) × 10⁴ M^?1 and K _1:1 = (8.8 ± 0.2) × 10⁴ M^?1 for 2 and 3, respectively, and K _1:1 = 73 ± 19 M^?1 and K _1:2 = 204 ± 65 M^?1 for 1. The comparison of K _1:1(3) with the product K _1:1 × K _1:2 (1) reveals that a chelate effect in binding the cholesterol by 3 exists. The structure of the cholesterol/3 complex was studied by ROESY experiments and by molecular dynamics simulations.     

Copper(I) halide complexes with N,N′-diallyl-N,N,N′,N′-tetramethylethylenediaminium (L2+). Synthesis and crystal structures of the complexes [L0.5CuCl2], [L0.5CuCl0.72Br1.28], and [L0.5CuBr2]

The Eschweiler-Clarke reaction of ethylenediamine with formaldehyde and formic acid yielded N,N,N′,N′-tetramethylethylenediamine, which was alkylated with allyl chloride or allyl bromide to give the corresponding N,N′-diallyl-N,N,N′,N′-tetramethylethylenediaminium (L²⁺) dihalides. In methanolic solutions of copper(II) halide and an appropriate ligand, ac electrochemical synthesis with copper wire electrodes afforded single crystals of Cu(I) complexes with L²⁺: [L_0.5CuCl₂] (I), [L_0.5CuCl_0.72Br_1.28] (II), and [L_0.5CuBr₂] (III). The crystal structures of complexes I–III were determined by X-ray diffraction study. The isostructural crystals of I and II are monoclinic, space group P2₁/n, Z = 4. For I: a = 7.632(4) Å, b = 11.318(5) Å, c = 10.635(5) Å, β = 98.551(7)°, V = 908.4(7) ų. For II: a = 7.7415(7) Å, b = 11.4652(9) Å, c = 10.7267(10) Å, β = 98.351(4)°, V = 942.0(2) ų. The organic cation L²⁺ acts as a bridge linking a pair of separate cuprous halide fragments Cu₂X₄. Although being isostoichiometric with I and II, complex III has a different structure. The crystals of III are monoclinic, space group P2₁/c, a = 6.519(2) Å, b = 9.060(3) Å, c = 16.284(6) Å, β = 97.219(4)°, V = 954.2(6) ų, Z = 4. In structure III, the inorganic fragment forms infinite polymer chains (CuBr ₂ ^? ) _n . The organic and inorganic parts are held together only by electrostatic interactions. Structures I–III are stabilized by hydrogen bonds (C)H…X (2.6–2.9 Å).     

Synthesis,structures and properties of three copper complexes created via in situ ligand cross-coupling reactions

Three copper complexes {[Cu₂(L¹)₂]·I₃} _n (1), [Cu(L²)₂] (2), and [Cu₂I₂(L³)₂(MBI)₂] (3) (MBI = 2-mercaptobenzimidazole, L¹ = N-(benzothiazol-2-yl)acetamidine anion, L² = N-(thiazol-2-yl) acetamidine anion, L³ = 3-methyl-[1,2,4]thiadiazolo[4,5-a]benzimidazole) have been synthesized solvothermally by the reactions of CuI with 2-benzothiazolamine, 2-aminothiazole and 2-mercaptobenzimidazole (MBI), respectively, in acetonitrile. In situ C–N (or C–S) cross-coupling ligand reactions were observed in all three complexes, and hypothetical reaction mechanisms are proposed for the formation of the ligands and their complexes. The single-crystal X-ray structural analysis reveals that both the Cu(II) and Cu(I) atoms are located in pseudo-tetrahedral environments in complex 1, and L¹ acts as a double bidentate ligand which coordinates with the Cu(I) and Cu(II) atoms to form a 1D coordination polymer. Unlike complex 1, the Cu(II) atom in complex 2 is in a square planar geometry, coordinated by two L² ligands with relatively small steric hindrance. In complex 3, the Cu(I) atoms have a distorted tetrahedral geometry, being coordinated by one nitrogen atom from L³, two sulfur atoms of MBI ligands, and one iodide. The sulfur atoms from MBI ligands bridge two Cu(I) atoms to form a binuclear complex. All three complexes exhibit relatively high thermal stabilities. Complex 1 displays intense fluorescence emission at 382 nm and complex 3 displays two intense fluorescence emissions at 401 and 555 nm.     

Tri- and tetraphenylantimony propiolates: Syntheses and structures

The reaction of triphenylantimony with propiolic acid in the presence of hydrogen peroxide (molar ratios 1 : 2 : 1 and 1 : 1 : 1) in diethyl ether affords triphenylantimony dipropiolate Ph₃Sb[OC(O)C≡CH]₂ (I) and μ₂-oxobis[(propiolato)triphenylantimony] [Ph₃SbOC(O)C≡CH]₂O (II). Tetraphenylantimony propiolate Ph₄SbOC(O)C≡CH (III) is synthesized from pentaphenylantimony and propiolic or acetylenedicarboxylic acid in toluene. According to the X-ray diffraction data, the crystals of compounds I and III include two types of crystallographically independent molecules (a and b). The antimony atoms in molecules Ia, Ib, II, IIIa, and IIIb have the trigonal-bipyramidal coordination mode with different degrees of distortion. The OSbO and OSbC axial angles are 176.8(2)° (Ia, Ib), 170.17(15)°, 178.78(14)° (II), and 173.2(5)°, 174.4(5)° (IIIa, IIIb). The CSbC equatorial angles lie in the ranges 108.2(3)°–143.1(3)° (I), 109.0(2)°–131.0(2)° (II), and 113.1(4)°–125.4(4)° (III). The SbOSb angle in II is 141.55(19)°. The Sb-C bond lengths are 2.103(8)–2.141(5) (I), 2.105(5)–2.119(5) (II), and 2.076(12)–2.166(13) Å (III). The Sb-O distances increase in a series of I, II, and III: 2.139(6)–2.156(7) (Ia, Ib); 2.206(4), 2.218(3) (II); and 2.338(10), 2.340(10) Å (III).     

Synthesis and thermal behavior study of complexes of the type [Pd(μ-X)(4-eb-p-phen)]2 (X = Cl,Br, I,N3, NCO,SCN) and 4-eb-p-phen [bis(4-ethylbenzyl)p-phenylenediimine]

The Schiff base bis(4-ethylbenzyl) p-phenylenediimine, 4-eb-p-phen (1), and six new dimeric Pd(II) complexes of the type [Pd(μ-X)(4-eb-p-phen)]₂ {X = Cl (2), Br (3), I (4), N₃ (5), NCO (6), SCN (7)} have been synthesized and characterized by elemental analysis, IR spectroscopy, and ¹H and ¹³C{¹H}-NMR experiments. The thermal behavior of the complexes 2–7 has been investigated by means of thermogravimetry and differential thermal analysis. From the final decomposition temperatures, the thermal stability of the complexes can be ordered in the following sequence: 3 > 4 > 7 > 2 ≈ 5 > 6. The final products of the thermal decompositions were characterized as metallic palladium by X-ray powder diffraction (XRD).     

Syntheses and crystal structures of oxovanadium(V) complexes derived from N′-[1-(2-hydroxynaphthyl)ethylidene]-4-nitrobenzohydrazide and 2-hydroxy-N′-[1-(2-hydroxynaphthyl)ethylidene]benzohydrazide

Reactions of bis(acetylacetonato)oxovanadium(IV) with N??-[1-(2-hydroxynaphthyl)ethylidene]-4-nitrobenzohydrazide (H₂HNB) and 2-hydroxy-N??-[1-(2-hydroxynaphthyl)ethylidene]benzohydrazide (H₂HHB), respectively, product two oxovanadium(V) species with the formulas [VO(OMe)(HNB)]₂ (I) and [VO(OMe)(HHB)] (II). The complexes I and II have been characterized by elemental analysis, IR spectra, and single crystal X-ray diffraction. The crystal of I is monoclinic: space group P2₁/n, a = 8.208(2), b = 14.528(3), c = 16.418(3) ?, ?? = 97.887(3)°, V = 1939.3(7) ?³, Z = 2. The crystal of II is triclinic: space group P $P\bar 1$ a = 8.334(2), b = 10.236(2), c = 11.337(2) ?, ?? = 80.91(3)°, ?? = 75.41(3)°, ?? = 75.63(3)°, V = 902.0(3) ?³, Z = 2. Complex I is a methoxide-bridged dimeric oxovanadium(V) complex, and complex II is a mononuclear oxovanadium(V) complex. The V atom in I is in an octahedral coordination, and that in II is in a square pyramidal coordination.