Formation of [CoCl4(H2O)2] complex in CoCl2·MgCl2·8H2O double salt: structural and energetic properties of [MCl4(H2O)2] and [M(H2O)6] (M=Mg, Co)

The crystal structure of the double salt CoCl₂·MgCl₂·8H₂O has been determined by the X-ray diffraction method. It crystallizes in the space group with a=6.0976(9), b=6.308(1), c=8.579(3) Å, α=81.99(2)°, β=88.40°, γ=84.61(1)°, Z=1, and R=0.027. The crystal consists of two kinds of well separated octahedra, [CoCl₄(H₂O)₂]²⁻ and [Mg(H₂O)₆]²⁺. The former is unique as aquachloro complexes of Co²⁺. In order to elucidate the reason prepared as such unique complexes in the double salts, formation energies for [MCl₄(H₂O)₂]²⁻ and [M(H₂O)₆]²⁺ (M=Co, Mg) have been calculated by using the density functional methods, and it has been revealed that the formation energies of the first coordination sphere for the metal ions and the Cl⁻?H₂O hydrogen bond networks around [CoCl₄(H₂O)₂]²⁻ play a decisive role in forming [CoCl₄(H₂O)₂]²⁻ with the regular octahedral geometry in the double salt.     

Syntheses and X-ray crystal structures of [Co(η-CO3)(NH3)4](NO3)·0.5H2O and [(NH3)3Co(μ-OH)2(μ-CO3)Co(NH3)3][NO3]2·H2O

[Co(η²-CO₃)(NH₃)₄](NO₃)·0.5H₂O and [(NH₃)₃Co(μ-OH)₂(μ-CO₃)Co(NH₃)₃][NO₃]₂·H₂O were prepared by prolonged aerial oxidation of a solution of Co(NO₃)₂·6H₂O and ammonium carbonate in aqueous ammonia. The formation of these side products highlights the richness of the chemistry of these systems and the possibility of by products if methods are not strictly adhered to. The X-ray crystal structures of [Co(η²-CO₃)(NH₃)₄][NO₃]·0.5H₂O and [(NH₃)₃Co(μ-OH)₂(μ-CO₃)Co(NH₃)₃][NO₃]₂·H₂O reveal a monomeric octahedral cobalt center with η²-bound CO₃²⁻ in the former, while the latter consists of a dimeric array where the two cobalt centers are bridged by two OH⁻ and one μ₂-CO₃²⁻ groups with three terminal NH₃ ligands for each Co center. In both complexes extensive hydrogen bonding interactions are evident.     

An efficient and rapid dehydrogenation of 4-aryl-3,4-dihydropyrimidin-2(1H)-ones (DHPMs) using CAN/HCl

An efficient and operationally simple method for the dehydrogenation of 4-aryl-3,4-dihydropyrimidin-2(1H)-ones (DHPMs) has been developed using CAN/HCl.     

Cu(OTf)2: a reusable catalyst for high-yield synthesis of 3,4-dihydropyrimidin-2(1H)-ones

Copper(II) triflate catalyzes efficiently the three-component condensation reaction of an aldehyde, β-ketoester and urea in acetonitrile to afford the corresponding 3,4-dihydropyrimidin-2(1H)-ones in high yields. The catalyst exhibited remarkable reusable activity.     

The role of anhydrous zinc nitrate in the thermal decomposition of the zinc hydroxy nitrates Zn5(OH)8(NO3)2·2H2O and ZnOHNO3·H2O

The steps associated with the thermal decomposition of Zn₅(OH)₈(NO₃)₂·2H₂O and ZnOHNO₃·H₂O are re-examined. Previous reports have suggested that Zn₅(OH)₈(NO₃)₂·2H₂O decomposes to ZnO via two intermediates, Zn₅(OH)₈(NO₃)₂ and Zn₃(OH)₄(NO₃)₂ whereas ZnOHNO₃·H₂O has been reported to decompose to ZnO via a Zn₃(OH)₄(NO₃)₂ intermediate. In this study, we demonstrate using TG, mass spectral analysis of evolved gases and in situ variable temperature powder X-ray diffraction analysis that, in fact, in the decomposition of Zn₅(OH)₈(NO₃)₂·2H₂O an anhydrous zinc nitrate intermediate is also involved. We, additionally, show that the decomposition of ZnOHNO₃·H₂O to ZnO also involves the formation of an anhydrous zinc nitrate intermediate. The anhydrous zinc nitrate formed in both cases is poorly crystallised and this observation may explain why this phase could not be observed by PXRD analysis in the previous studies.     

Synthesis of C2-functionalized pyrimidines from 3,4-dihydropyrimidin-2(1H)-ones by the Mitsunobu coupling reaction

The Biginelli 3,4-dihydropyrimidin-2(1H)-one was converted to various C2-multifunctionalized pyrimidines via the dehydrogenation and Mitsunobu reaction using amines, alcohols, phenols and carboxylic acids as nucleophiles. A possible mechanism was also proposed to rationalize the formation of products.     

Syntheses and characterization of Co(pydc)(H2O)2 and Ni(pydc)(H2O) (pydc = 3,5-pyridinedicarboxylate)

The hydrothermal reaction of 3,5-pyridinedicarboxylic acid (pydcH₂) and Co(NO₃)₂ or Ni(NO₃)₂ in the presence of 4,4′-bipyridine results in two novel compounds Co(pydc)(H₂O)₂ (1) and Ni(pydc)(H₂O) (2). Crystal data: 1, monoclinic, C2/c, a=9.900(2), b=11.984(2), c=7.3748(15) Å, β=105.37(3)°, V=843.7(3) Å³, Z=4; 2, monoclinic, P2₁/c, a=7.7496(6), b=15.0496(11), c=6.4224(5) Å, β=108.437(1)°, V=710.59(9) Å³, Z=4. The structure of 1 is composed of honeycomb layers built up from {CoO₄N} trigonal bipyramids and 3,5-pyridinedicarboxylate bridges. The structure of 2 adopts a three-dimensional framework structure in which the Ni atoms are coordinated by the pydc bridges both within the honeycomb layer and between the layers. The magnetic properties of 1 and 2 have been investigated.     

Thermal decomposition of syngenite, K2Ca(SO4)2·H2O

The thermal decomposition of syngenite, K₂Ca(SO₄)₂·H₂O, formed during the treatment of liquid manure has been studied by thermal gravimetric analysis, differential scanning calorimetry, high temperature X-ray diffraction (XRD) and infrared emission spectroscopy (IES). Gypsum was found as a minor impurity resulting in a minor weight loss due to dehydration around 100 °C. The main endothermic dehydration and decomposition stage of syngenite to crystalline K₂Ca₂(SO₄)₃ and amorphous K₂SO₄ is observed around 200 °C. The reaction involves a solid-state re-crystallisation, while water and the K₂SO₄ diffuse out of the existing lattice. The additional weight loss steps around 250 and 350 °C are probably due to presence of larger syngenite particles, which exhibit slower decomposition due to the slower diffusion of water and K₂SO₄ out of the crystal lattice. A minor endothermic sulphate loss around 450 °C is not due to the decomposition of syngenite or its products or of the gypsum impurity. The origin of this sulphate is not clear.     

Thermal decomposition of Cu(NO3)2·3H2O at reduced pressures

Thermolysis of Cu(NO₃)₂·3H₂O is studied by means of XRD analysis in situ and mass spectral analysis of the gas phase at P=1/10 Pa at low heating rate. It is shown that stage I of the dehydration (40-80 °C) results in the consecutive appearance of crystalline Cu(NO₃)₂·2.5H₂O and Cu(NO₃)·H₂O. Anhydrous Cu(NO₃)₂ formed during further dehydration at 80-110 °C is moderately sublimed at 120-150 °C. Dehydration is accompanied by thermohydrolysis, leading to the appearance of Cu₂(OH)₃NO₃ and gaseous H₂O, HNO₃, NO₂, and H₂O. The higher pressure in the system, the larger amount of thermohydrolysis products is observed. The formation of the crystalline intermediate CuO_x(NO₃)_y was observed by diffraction methods. Final product of thermolysis (CuO) is formed at 200-250 °C.     

Regioselective dehydrogenation of 3,4-dihydropyrimidin-2(1H)-ones mediated by ceric ammonium nitrate

Ceric ammonium nitrate (CAN) has been explored for the regioselective oxidation of 3,4-dihydropyrimidin-2(1H)-ones (DHPMs). Interestingly, we obtained ethyl 2,4-dioxo-6-phenyl-tetrahydropyrimidin-5-carboxylates as the major products during the oxidation of DHPMs by CAN/AcOH at 80 °C. The reaction afforded a mixture of products while employing CAN in organic solvents without additives. However, the regioselective dehydrogenated product, ethyl 6-methyl-4-aryl(alkyl)-pyrimidin-2(1H)-one-5-carboxylate was obtained by performing the reaction with NaHCO₃. The single crystal X-ray crystallography of ethyl 6-methyl-4-(2-phenyl)-pyrimidin-2(1H)-one-5-carboxylate revealed that the oxidized product existed in amidic form rather than aromatized enol form of pyrimidines. The efficiency of the present protocol enabled the synthesis of structurally diverse pyrimidines in moderate to good yields under milder reaction conditions.     

Structural and spectroscopic properties of Hexamethylenetetramine cobalt(II) complex: [Co(NCS)2(hmt)2(H2O)2][Co(NCS)2(H2O)4] (H2O)

Synthesis, structure, spectroscopy and thermal properties of complex [Co(NCS)₂(hmt)₂(H₂O)₂][Co(NCS)₂(H₂O)₄] (H₂O) (I), assembled by hexamethylenetetramine and octahedral Co(II) metal ions, are reported. Crystal data for I: F_w 387.34, a=9.020(8), b=12.887(9), c=7.95(1) Å, =96.73(4), β=115.36(5), γ=94.16(4)°, V=820(1) Å³, Z=2, space group=P−1, T=173 K, λ(Mo-K)=0.71070 Å, ρ_calc=1.718567 g cm⁻³, μ=17.44 cm⁻¹, R=0.088, R_w=0.148. An interesting two-dimensional network is assembled via hydrogen bonds through coordinated and free water molecules. The d–d transition energy levels of Co(II) ion are determined by UV–vis spectroscopy and calculated by ligand field theory. The calculated results agree well with experiment ones.     

Syntheses and structures of three new scandium selenites: Sc2(SeO3)3·H2O, Sc2 (SeO3)3·3H2O and CsSc3(SeO3)4 (HSeO3)2·2H2O

Three new hydrated scandium selenites have been hydrothermally synthesized as single crystals and structurally and physically characterized. Sc₂(SeO₃)₃·H₂O crystallizes as a new structure type containing novel ScO₇ pentagonal bipyramidal and ScO₆₊₁ capped octahedral coordination polyhedra. Sc₂(SeO₃)₃·3H₂O contains typical ScO₆ octahedra and is isostructural with its M₂(SeO₃)₃·3H₂O (M=Al, Cr, Fe, Ga) congeners. CsSc₃(SeO₃)₄(HSeO₃)₂·2H₂O contains near-regular ScO₆ octahedra and has essentially the same structure as its indium-containing analogue. All three phases contain the expected pyramidal [SeO₃]^2- selenite groups. Crystal data: Sc₂(SeO₃)₃·3H₂O, M_r=524.85, trigonal, R3c (No. 161), , , , Z=6, R(F)=0.018, wR(F²)=0.036; Sc₂(SeO₃)₃·H₂O, M_r=488.82, orthorhombic, P2₁2₁2₁ (No. 19), , , , , Z=4, R(F)=0.051, wR(F²)=0.086; CsSc₃(SeO₃)₄(HSeO₃)₂·2H₂O, M_r=1067.60, orthorhombic, Pnma (No. 62), , , , , Z=4, R(F)=0.035, wR(F²)=0.070.     

Propane phosphonic acid anhydride: a new promoter for the one-pot Biginelli synthesis of 3,4-dihydropyrimidin-2(1H)-ones

Propane phosphonic acid anhydride has been found to promote the Biginelli synthesis of 3,4-dihydropyrimidin-2(1H)-ones. The use of this agent is characterized by moderate costs, low toxicity and simple workup conditions.     

Hydrothermal synthesis and structure of one-dimensional Co(dien)2(VO3)3·(H2O) (dien=diethylenetriamine)

One-dimensional Co(dien)₂(VO₃)₃·(H₂O) was prepared from the hydrothermal reaction of NH₄VO₃, Co₂O₃, diethylenetriamine (dien) and H₂O at 130 °C. The compound crystallizes in the monoclinic system, space group P2₁/c with a=16.1581(6) Å, b=8.7006(3) Å, c=13.9893(4) Å, β=103.1483(11)°, V=1915.13(11) Å³, Z=4, and R₁=0.0268 for 3060 observed reflections. Single crystal X-ray diffraction revealed that the structure is composed of infinite one-dimensional chains formed by corner-sharing VO₄ tetrahedra with Co(dien)³⁺ complex cations and crystallization water molecules occupying the interchain positions, which are held together to a three-dimensional network via extensive hydrogen-bonding interactions. The compound, with a new zig-zag conformation of metavanadate chains, is the first example of vanadium oxides incorporating trivalent transition metal coordination groups. Other characterizations by elemental analysis, IR and thermal analysis are also described.     

Co3{CH3C(NH3)(PO3H)(PO3)}2 {CH3C(NH3)(PO3H)2}2(H2O)4·2H2O: A cobalt 1-aminoethylidenediphosphonate with a layer structure

This paper describes the structure and magnetic properties of a novel cobalt 1-aminoethylidenediphosphonate compound, namely Co₃{CH₃C(NH₃)(PO₃H)(PO₃)}₂{CH₃C(NH₃)(PO₃H)₂}₂(H₂O)₄·2H₂O (1). The structure contains a trimer unit of Co₃{CH₃C(NH₃)(PO₃H)(PO₃)}₂ in which two equivalent phosphonate ligands chelate and bridge the three cobalt ions. Each trimer unit is further linked to its four equivalent neighbors through corner-sharing of CoO₆ octahedra and CPO₃ tetrahedra, forming a two-dimensional layer in the bc-plane which contains 12-membered rings. These layers are connected to each other by extensive hydrogen bonds. Magnetic studies show that weak antiferromagnetic interactions are mediated between the cobalt ions. Crystal data for 1: monoclinic, space group C2/c, a=27.727(4), b=7.1091(11), , β=118.488(3), , Z=2.     

Conductivities of the Ternary Systems Y(NO3)3+La(NO3)3+H2O, La(NO3)3+Ce(NO3)3+H2O, La(NO3)3+Nd(NO3)3+H2O and Their Binary Subsystems at Different Temperatures

Electrical conductivities were measured for the ternary systems Y(NO₃)₃+La(NO₃)₃+H₂O, La(NO₃)₃+Ce(NO₃)₃+H₂O, La(NO₃)₃+Nd(NO₃)₃+H₂O, and their binary subsystems Y(NO₃)₃+H₂O, La(NO₃)₃+H₂O, Ce(NO₃)₃+H₂O, and Nd(NO₃)₃+H₂O at (293.15, 298.15 and 308.15) K. The measured conductivities were used to test the generalized Young’s rule and the semi-ideal solution theory. The comparison results show that the generalized Young’s rule and the semi-ideal solution theory can yield good predictions for the conductivities of the ternary electrolyte solutions, implying that the conductivities of aqueous solutions of (1:3 + 1:3) electrolyte mixtures can be well predicted from those of their constituent binary solutions by the simple equations.     

Bimetallic single-source precursors [M(NH3)4][Co(C2O4)2(H2O)2]·2H2O (M = Pd, Pt) for the one run synthesis of CoPd and CoPt magnetic nanoalloys

All the steps of the proposed technique, from the synthesis of single-source precursors to the preparation of CoPd and CoPt nanoalloys, are described. The double complex salts (DCS) [M(NH₃)₄][Co(C₂O₄)₂(H₂O)₂]·2H₂O (M = Pd, Pt), which were synthesized by mixing solutions containing [M(NH₃)₄]²⁺ cations and [Co(C₂O₄)₂(H₂O)₂]²⁻ anions, have been used as precursors. The salts obtained were characterized by IR spectroscopy, thermal analysis, XRD and single crystal X-ray diffraction. The prepared compounds crystallize in the monoclinic (space group I2/m, M = Pd) and orthorhombic (space group I222, M = Pt) crystal systems. Thermal decomposition of the salts in helium or hydrogen atmosphere at 200-600 °C results in the formation of nanoalloys powders (random solid solution Co_0.50Pd_0.50 and chemically ordered CoPt). The size of the bimetallic particles varied from 5 to 20 nm. Order-disorder structural transformations in Co_0.50Pt_0.50 nanoalloys were studied. The magnetic properties of both chemically disordered Co_0.50Pd_0.50 and ordered CoPt clusters have also been measured.     

Ho(NO3)3(C2H5O2N)4·H2O的低温热容和热力学函数

合成了稀土(钬, Ho)-氨基酸(甘氨酸, C₂H₅O₂N)二元配合物Ho(NO₃)₃(C₂H₅O₂N)₄·H₂O, 并且通过化学分析、元素分析和红外(IR)光谱对配合物进行了表征. 用高精度全自动绝热量热仪, 测定了该配合物在80-390 K温度区间的定压摩尔热容(C_p,m). 利用实验测定的热容数据, 采用最小二乘法, 将热容曲线上热容峰以外的两段平滑区的摩尔热容对折合温度进行拟合, 建立了热容随折合温度变化的多项式方程. 根据热容与焓、熵的热力学关系,计算出了配合物在80-390 K温度区间内,每隔5 K,相对于298.15 K的摩尔热力学函数(H_T,m-H_298.15,m)和(S_T,m-S_298.15,m). 通过热容曲线分析, 计算出了350 K附近转变过程的焓变(Δ_trsH_m)和熵变(Δ_trsS_m). 用差示扫描量热法(DSC)测定了配合物的热稳定性.     

Solvothermal synthesis, crystal structure, magnetic and luminescent properties of (H3O)6·[Co4(H2O)4(HPMIDA)2(PMIDA)2)]·2H2O

A cobalt phosphonate (H₃O)₆·[Co₄(H₂O)₄(HPMIDA)₂(PMIDA)₂)]·2H₂O, 1, has been synthesized from a mild solvothermal reaction of Co(II) ion with N-(phosphonomethyl)iminodiacetic acid (H₄PMIDA). Compound 1 crystallizes in the triclinic space group with cell parameters of , , , α=93.06(3)°, β=99.66(3)°, γ=90.34(3)° and Z=1. Compound 1 shows a novel tetra-nuclear molecular structure. In the crystal lattice, molecules of 1 hydrogen bond to each other to form two-dimensional (2D) layers, which are further linked together by the co-crystallized H₂O molecules and H₃O⁺ counter ions through hydrogen bonding to form the 3D supramolecular network. Thermogravimetric analysis, IR spectrum, magnetic susceptibility and luminescent spectra are given.     

Syntheses and structural determination of nine-coordinate K3[Nd(nta)2(H2O)]·6H2O and K3[Er(nta)2(H2O)]·5H2O

The syntheses and structural determination of Nd^III and Er^III complexes with nitrilotriacetic acid (nta) were reported in this paper. Their crystal and molecular structures and compositions were determined by single-crystal X-ray structure analyses and elemental analyses, respectively. The crystal of K₃[Nd^III(nta)₂(H₂O)]·6H₂O complex belongs to monoclinic crystal system and C2/c space group. The crystal data are as follows: a=1.5490(11) nm, b=1.3028(9) nm, c=2.6237(18) nm, β=96.803(10)°, V=5.257(6) nm³, Z=8, M=763.89, D_c=1.930 g cm⁻³, μ=2.535 mm⁻¹ and F(000)=3048. The final R₁ and wR₁ are 0.0390 and 0.0703 for 4501 (I>2σ(I)) unique reflections, R₂ and wR₂ are 0.0758 and 0.0783 for all 10474 reflections, respectively. The Nd^IIIN₂O₇ part in the [Nd^III(nta)₂(H₂O)]³⁻ complex anion has a pseudo-monocapped square antiprismatic nine-coordinate structure in which the eight coordinate atoms (two N and six O) are from the two nta ligands and a water molecule coordinate to the central Nd^III ion directly. The crystal of the K₃[Er^III(nta)₂(H₂O)]·5H₂O complex also belongs to monoclinic crystal system and C2/c space group. The crystal data are as follows: a=1.5343(5) nm, b=1.2880(4) nm, c=2.6154(8) nm, b=96.033(5)°, V=5.140(3) nm³, Z=8, M=768.89, D_c=1.987 g cm⁻³, μ=3.833 mm⁻¹ and F(000)=3032. The final R₁ and wR₁ are 0.0321 and 0.0671 for 4445 (I>2σ(I)) unique reflections, R₂ and wR₂ are 0.0432 and 0.0699 for all 10207 reflections, respectively. The Er^IIIN₂O₇ part in the [Er^III(nta)₂(H₂O)]³⁻ complex anion has the same structure as Nd^IIIN₂O₇ part in which the eight coordinate atoms (two N and six O) are from the two nta ligands and a water molecule coordinate to the central Nd^III ion directly.