An unusual oxidation-dealkylation of 3,4-dihydropyrimidin-2(1H)-ones mediated by Co(NO3)2·6H2O/K2S2O8 in aqueous acetonitrile

4-Aryl-6-methyl-3,4-dihydropyrimidin-2(1H)-one (DHPM) scaffolds of Biginelli type were oxidized using Co(II)/S₂O₈²⁻ and the reaction afforded 6-unsubstituted pyrimidin-2(1H)-ones through an unprecedented dealkylation process. 4-Alkyl DHPMs under similar conditions afforded yet another unusual product, ethyl tetrahydropyrimidin-2,4(1H,3H)-dione-5-carboxylate.     

Elektronenstossinduzierte Fragmentierung von Acetylenverbindungen—VI: Struktur und Bildungsenthalpie der Ionen [C11H9]+ und [C9H7]+

The appearance potentials for [C₁₁H₉]⁺ from 1, e.g. 2-(chloromethyl)-naphthaline and 1-chloro-phenyl-(5)-penten-(2)-yne-(4), and for [C₉H₇]⁺ from indene, phenyl-propyne and phenyl-(5) penten-(2)-yne-(4)-ol-(1), have been correlated with thermochemical data to obtain the enthalpy of formation of the fragment-ions. A comparison between these enthalpies of formation and the values of enthalpy of hypothetical model structures shows that the [C₁₁H₉]⁺ ion is probably best represented as a benztropylium-ion and the [C₉H₇]⁺ ion as an ethynyl-tropylium-ion or as a phenylcyclopropenyl-cation. Open chain structures can be eliminated in all cases investigated.     

Theoretical study of H2 elimination from [B n H n + 1]− monoanions (n = 6–9, 11)

Transition states of elementary reactions of H₂ molecule elimination from [B _n H _{n + 1}]^? anions (n = 6–9, 11) in which nucleophilic/electrophilic vacancies form at boron atoms have been localized by the density functional theory method (in the B3LYP/6-311++G** approximation). For a series of [B _n H _{n + 1}]^? anions (n = 6–12), the activation barriers to H2 elimination have been compared to consider the possibility of substitution for exopolyhedral hydrogen atoms by the mechanism with the first rate-limiting stage of formation of [B _n H _{n ? 1}]^? (n = 6–12) intermediates with a vacant “bare” vertex of the boron cluster. For the [B _n H _n ]^2?, [B _n H _{n + 1}]^?, and [B _n H _{n ? 1}]^? anions (n = 6–12), the electronic chemical potential μ and Pearson hardness η have been evaluated since these characteristics make it possible to assess the propensity of different reagents to react with each other in terms of the empirical HSAB principle (soft with soft and hard with hard). The application of this principle is exemplified by the interaction of the [B₁₀H₉]^? and [B₁₂H₁₁]^? anions with acetonitrile CH₃CN, furan C₄H₄O, and 18-crown-6.     

Difunctionalized {closo‐1‐CB11} Clusters: 1‐ and 2‐Amino‐12‐ethynylcarba‐closo‐dodecaborates

Carba‐closo‐dodecaborate anions with two functional groups have been synthesized via a simple two‐step procedure starting from monoamino‐functionalized {closo‐1‐CB₁₁} clusters. Iodination at the antipodal boron atom provided access to [1‐H₂N‐12‐I‐closo‐1‐CB₁₁H₁₀]^? ( 1 a ) and [2‐H₂N‐12‐I‐closo‐1‐CB₁₁H₁₀]^? ( 2 a ), which have been transformed into the anions [1‐H₂N‐12‐RC?C‐closo‐1‐CB₁₁H₁₀]^? (R=H ( 1 b ), Ph ( 1 c ), Et₃Si ( 1 d )) and [2‐H₂N‐12‐RC?C‐closo‐1‐CB₁₁H₁₀]^? (R=H ( 2 b ), Ph ( 2 c ), Et₃Si ( 2 d )) by microwave‐assisted Kumada‐type cross‐coupling reactions. The syntheses of the inner salts 1‐Me₃N‐12‐RC?C‐closo‐1‐CB₁₁H₁₀ (R=H ( 1 e ), Et₃Si ( 1 f )) and 2‐Me₃N‐12‐RC?C‐closo‐1‐CB₁₁H₁₀ (R=H ( 2 e ), Et₃Si ( 2 f )) are the first examples for a further derivatization of the new anions. All {closo‐1‐CB₁₁} clusters have been characterized by multinuclear NMR and vibrational spectroscopy as well as by mass spectrometry. The crystal structures of Cs 1 a , [Et₄N] 2 a , K 1 b , [Et₄N] 1 c , [Et₄N] 2 c , 1 e , and [Et₄N][1‐H₂N‐2‐F‐12‐I‐closo‐1‐CB₁₁H₉]?0.5 H₂O ([Et₄N ]4 a ?0.5 H₂O) have been determined. Experimental spectroscopic data and especially spectroscopic data and bond properties derived from DFT calculations provide some information on the importance of inductive and resonance‐type effects for the transfer of electronic effects through the {closo‐1‐CB₁₁} cage.     

Synthesis, characterization, crystal and molecular structure analysis of N-(2,4-dimethylphenyl)-6-methyl-4-(3-nitrophenyl)-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxamide

A novel dihydropyrimidine (DHPM) derivative bearing a carbamoyl moiety was synthesized by an efficient three-component Biginelli reaction and was characterized spectroscopically and finally confirmed by X-ray diffraction studies. The title compound C₂₀H₂₀N₄O₄ crystallizes in the monoclinic space group P2₁/c with cell parameters a=12.8970(12) Å, b=13.6210(11) Å, c=11.8420(13) Å, β=115.860(3)°, Z=4 and V=1872.0(3) Å³. The conformation of the dihydropyrimidine ring is unusual; it is planar instead of the usual boat-like conformation. The 3-nitrophenyl ring is orthogonal to the 3,4-DHPM ring. The carbonyl group is in an anti-clinal conformation.     

The standard enthalpies of formation of cyclohexylamine and cyclohexylamine hydrochloride

The standard enthalpy of combustion of cyclohexylamine has been measured in an aneroid rotating-bomb calorimeter. The value ΔH_o^o(c-C₆H₁₁NH₂, 1) = ?(4071.3 ± 1.3) kJ mol^?1 yields the standard enthalpy of formation ΔH_f^o(c-C₆H₁₁NH₂, 1) = ?(147.7 ± 1.3) kJ mol^?1. The corresponding gas-phase standard enthalpy of formation for cyclohexylamine is ΔH_f^o(c-C₆H₁₁NH₂, g) = ?(104.9 ± 1.3) kJ mol^?1. The standard enthalpy of formation of cyclohexylamine hydrochloride, ΔH_f^o(c-C₆H₁₁NH₂·HCl, c) = ?(408.2 ± 1.5) kJ mol^?1, was derived by combining the measured enthalpy of solution of the salt in water, literature data, and the ΔH_c^o measured in this study. Comment is made on the thermochemical bond enthalpy H(CN).     

Syntheses,structures and properties of four organic–inorganic hybrid nicotinate-bridging rare-earth-containing phosphotungstates

Four novel organic–inorganic hybrid nicotinate-bridging dimeric rare-earth (RE)-containing phosphotungstates [H₂N(CH₃)₂]₈[RE(H₂O)(NA)(α-HPW₁₁O₃₉)]₂·24H₂O (RE = Ho^III for 1, Er^III for 2, Tb^III for 3, Dy^III for 4; HNA = nicotinic acid) have been synthesized from the reaction of trivacant Keggin precursor Na₉[α-PW₉O₃₄]∙16H₂O, RE(NO₃)₃·6H₂O, HNA by employing dimethylamine hydrochloride as organic solubilizing agent in the conventional aqueous solution system, which have been further characterized by elemental analyses, IR spectra, thermogravimetric analyses and single-crystal X-ray diffraction. Structural analysis indicates that the hybrid dimeric {[RE(H₂O)(NA)(α-HPW₁₁O₃₉)]₂}⁸⁻ polyoxoanion in 1–4 can be considered as two head-to-head mono-RE-containing Keggin [RE(H₂O)(NA)(α-HPW₁₁O₃₉)]⁴⁻ subunits bridged by two (η²,μ-1,1)-nicotinate linkers, which stands for the first organic–inorganic hybrid RE-containing phosphotungstates functionalized by nicotinate ligands. What's more, the solid-state photoluminescence properties and lifetime decay behaviors of 1–4 have been measured at room temperature and their photoluminescence spectra display the characteristic emission bands of corresponding trivalent RE cations.     

Some Novel Dinuclear phenylboronates of biologically potent β‐enaminoesters: Synthesis,Spectroscopic characterization,antimicrobial activity and their antiandrogenic effect

Organoboron derivatives of biologically potent β‐enamino esters of the type [Where R = CH₃(1a), C₂H₅ (1b), C₃H₇(1c) and C (CH₃)₃ (1d)] have been prepared by the reactions of β‐enamino esters and Phenyl boronic acid [PhB (OH)₂] in 1:2 molar ratio in refluxing tetrahydrofuran (THF). All these derivatives have been characterized by physico‐chemical properties, elemental analyses and molecular weight measurements. The structures of these compounds have been proposed on the basis of IR, ¹H, ¹³C, ¹¹B NMR spectral data and GC‐mass spectrometry. Phenyl boronic acid, β‐enamino esters and their respective phenylboronates derivatives have been screened for the antibmicrobial activities against pathogenic bacteria (B. subtilis and E. coli) and fungi (A. niger and P. peniculosum) to access their growth inhibiting potential. In addition to this, antiandrogenic effect of Ligand, L^aH₂ and its boron derivative (1a) has also been tested in male albino rats.     

Preparation of ultrafine metal particles in processes of pulse mechanical action

Ultrafine metal particles (UFMP) (iron and cobalt) have been obtained in solid-state redox reactions of cyclopentadienyl--(3)-1,2-dicarbollyliron or cyclopentadienyl--(3)-1,2-dicarbollylcobalt with elemental sulfur ((C₅H₅)Fe³⁺(C₂B₉H₁₁)-S, (C₅H₅)Co⁵⁺C₂B₉H₁₁-S). These reactions are realized by the action of elastic wave (EW) pulses on powder compositions of these substances. Study of the UFMP obtained by the ferromagnetic resonance (FMR) method has shown that the sizes ofn · Co⁰ UFP lie in the range from 1 to 13 nm. UFP of cobalt and iron are also formed under the action of EW on samples containing (C₅H₅)Fe³⁺(C₂B₉H₁₁)-S or (C₅H₅)Co³⁺(C₂B₉H₁₁)-S within the film of tetrafluoroethylene and perfluoro-4-methyl-3,6-dioxaoct-7-ene-1-sulfonyl fluoride copolymer (CP). It is shown by the FMR method that FMR lines broaden on going from powder systems to systems containing CP films. It is supposed thatn · Co⁰ and n · Fe⁰ particles interact with polymeric matrices in the course of formation and stabilization of UFMP in the matrices.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2355–2358, December, 1995.This work was financially supported by the Russian Foundation for Basic Research (Project No. 94-03-09632).     

Catalytic effects of [Ag(H2O)(H3PW11O39)]3− on a TiO2 anode for water oxidation

A [H₃Ag^I(H₂O)PW₁₁O₃₉]^3?-TiO₂/ITO electrode was fabricated by immobilizing a molecular polyoxometalate-based water oxidation catalyst, [H₃Ag^I(H₂O)PW₁₁O₃₉]^3? (AgPW₁₁), on a TiO₂ electrode. The resulting electrode was characterized by X-ray powder diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Linear sweep voltammetry, chronoamperometry, and electrochemical impedance measurements were performed in aqueous Na₂SO₄ solution (0.1 mol L^?1). We found that a higher applied voltage led to better catalytic performance by AgPW₁₁. The AgPW₁₁-TiO₂/ITO electrode gave currents respectively 10 and 2.5 times as high as those of the TiO₂/ITO and AgNO₃-TiO₂/ITO electrodes at an applied voltage of 1.5 V vs Ag/AgCl. This result was attributed to the lower charge transfer resistance at the electrode-electrolyte interface for the AgPW₁₁-TiO₂/ITO electrode. Under illumination, the photocurrent was not obviously enhanced although the total anode current increased. The AgPW₁₁-TiO₂/ITO electrode was relatively stable. Cyclic voltammetry of AgPW₁₁ was performed in phosphate buffer solution (0.1 mol L^?1). We found that oxidation of AgPW₁₁ was a quasi-reversible process related to one-electron and one-proton transfer. We deduced that disproportionation of the oxidized [H₂Ag^II(H₂O)PW₁₁O₃₉]^3? might have occurred and the resulting [H₃Ag^IIIOPW₁₁O₃₉]^3? oxidized water to O₂.     

Synthesis of a new N,N-ethane-1,2-bis(4-methoxyphenyl)carbothioamide ligand and its Cu(I) and Ag(I) complexes

[Cu(H₂L)(PPh₃)₂]NO₃ · 0.5H₂O (2) and [Ag(H₂L)(PPh₃)₂]NO₃ · 0.5H₂O (3) complexes of a new flexible thioamide ligand; N,N′-ethane-1,2-bis(4-methoxyphenyl)carbothioamide H₂L (1) have been synthesized using PPh₃ as a coligand. The synthesized compounds have been characterized with the help of elemental analyses, IR, ¹H, ¹³C and ³¹P NMR spectroscopy. The ligand and its Cu(I) complex have been studied by single crystal X-ray crystallography. The ligand acts as a neutral S-donor and forms a nine-membered chelate ring in [Cu(H₂L)(PPh₃)₂]NO₃ · 0.5H₂O. The molecular packing is stabilized by an anionic cavity formed by intermolecular hydrogen bonding between the basal plane of the complex molecule and the nitrate ions. The square shaped columnar channel has dimensions of 5.489(25) [N(11)–H(11A)?O(13)?H(21A)N(21)] × 3.693(7) [N(11)–C(11)–C(21)–N(21)] Å.     

Neutron scattering study of the reorientational motions in Cr(CO)3(η6C6H6) and Mn(CO)3(η5C5H5)

Incoherent quasi-eleastic neutron scattering experiments: using different resolutions and a wide Q range, have been performed on polycrystalline samples of Cr(CO)₃(η⁶C₆H₆) and Mn(CO)₃(η⁵C₅H₅) in the 280–320 K temperature range. It is shown that aromatic rings are involved into a reorientational process characterized by an activation energy of ≈ 16 kJ mol^?1 and by correlation times of the order of 2 × 10^?11 s and 5 × 10^?11 s at 300 K for C₆H₆ and C₅H₅ rings respectively. Experimental elastic incoherent structure factors are in agreement with the 2π/6 and 2π/5 jump models and the fitted spectra confirm these models. From a comparison with heat-capacity results we conclude that M(CO)₃ groups are fixed during the reorientational process. Finally a comparison with literature data is presented.     

Cobalt(II), nickel(II), and copper(II) complexes of 14-membered hexaazamacrocycles: synthesis and characterization

Cobalt(II), nickel(II), and copper(II) complexes containing 5,12-di(4-bromophenyl)-7,14-dimethyl-1,2,4,8,9,11-hexaazacyclotetradeca-7,14-diene-3,10-dione (H₂L¹) and 5,12-diphenyl-7,14-dimethyl-1,2,4,8,9,11-hexaazacyclotetradeca-7,14-diene-3,10-dione (H₂L²) have been synthesized. All complexes were characterized by elemental analysis, MALDI TOF-MS spectrometry, and electronic absorption spectroscopy. The crystal structures of two compounds, [Cu₂(H₂L¹)Cl₄]_n and [NiL²], were determined by X-ray powder diffraction. In the polymeric [Cu₂(H₂L¹)Cl₄]_n, the Cu₂Cl₄ units and H₂L¹ molecules are situated on inversion centers. Each Cu(II) has a distorted trigonal-bipyramidal coordination environment formed by N and O from H₂L¹ [Cu–N 2.340(14)?Å, Cu–O 1.952(11)?Å], two bridging chlorides [Cu–Cl 2.332(5), 2.279(5)?Å] and one terminal chloride [Cu–Cl 2.320(6)?Å]. In the [NiL²] complex, the Ni(II) situated on inversion center has a distorted square-planar coordination environment formed by four nitrogens from L² [Ni–N 1.860(11), 1.900(11)?Å].     

Synthesis of metal complexes with a novel ethyldioxolane pendant-arm hexaazamacrocyclic ligand

The coordination capability of a pendant-arm azamacrocyclic ligand L with four ethyldioxolane pendant groups towards transition, post-transition and lanthanide metal ions was achieved. In all cases, complexes with a 2:1 metal:ligand molar ratio were obtained. The complexes were characterized by elemental analysis, MS-FAB, IR, conductivity measurements, ¹H and ¹³C NMR spectroscopy. Crystal structures of [CoL][CoBr_0.5(NO₃)_3.5] and [(H₂O)H₂L][Nd(NO₃)₄(H₂O)₃]NO₃·3.5H₂O have been determined. The [CoL]²⁺ cation contains the Co(II) ion endomacrocyclicly coordinated in a distorted octahedral geometry with a N₆ core. The Nd(III) complex presents a mononuclear exomacrocyclic structure with an 11 coordination environment. π,π-Stacking interactions have been observed between the pyridine rings of the protonated ligand [(H₂O)H₂L]²⁺, and the [Nd(NO₃)₄(H₂O)₃]²⁻ anion.     

Kinetics of phenyl radical reactions with propane,n‐butane,n‐hexane,and n‐octane: Reactivity of C6H5 toward the secondary C?H bond of alkanes

The kinetics of C₆H₅ reactions with n‐C_nH_2n+2 (n = 3, 4, 6, 8) have been studied by the pulsed laser photolysis/mass spectrometric method using C₆H₅COCH₃ as the phenyl precursor at temperatures between 494 and 1051 K. The rate constants were determined by kinetic modeling of the absolute yields of C₆H₆ at each temperature. Another major product C₆H₅CH₃ formed by the recombination of C₆H₅ and CH₃ could also be quantitatively modeled using the known rate constant for the reaction. A weighted least‐squares analysis of the four sets of data gave k (C₃H₈) = (1.96 ± 0.15) × 10¹¹ exp[?(1938 ± 56)/T], and k (n‐C₄H₁₀) = (2.65 ± 0.23) × 10¹¹ exp[?(1950 ± 55)/T] k (n‐C₆H₁₄) = (4.56 ± 0.21) × 10¹¹ exp[?(1735 ± 55)/T], and k (n?C₈H₁₈) = (4.31 ± 0.39) × 10¹¹ exp[?(1415 ± 65)T] cm³ mol^?1 s^?1 for the temperature range studied. For the butane and hexane reactions, we have also applied the CRDS technique to extend our temperature range down to 297 K; the results obtained by the decay of C₆H₅ with CRDS agree fully with those determined by absolute product yield measurements with PLP/MS. Weighted least‐squares analyses of these two sets of data gave rise to k (n?C₄H₁₀) = (2.70 ± 0.15) × 10¹¹ exp[?(1880 ± 127)/T] and k (n?C₆H₁₄) = (4.81 ± 0.30) × 10¹¹ exp[?(1780 ± 133)/T] cm³ mol^?1 s^?1 for the temperature range 297‐‐1046 K. From the absolute rate constants for the two larger molecular reactions (C₆H₅ + n‐C₆H₁₄ and n‐C₈H₁₈), we derived the rate constant for H‐abstraction from a secondary C? H bond, k_s?CH = (4.19 ± 0.24) × 10¹⁰ exp[?(1770 ± 48)/T] cm³ mol^?1 s^?1. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 49–56, 2004     

Undecaborates M2[B11H11]: Facile Synthesis,Crystal Structure,and Reactions

closo-Undecaborates were synthesized by the deprotonation of B₁₁H₁₃(SMe₂) with LitBu in thp or K[BHEt₃] in thf, [Li(thp)₃]₂[B₁₁H₁₁] and K₂[B₁₁H₁₁] being obtained in 83 and 93% yield, respectively. K₂[B₁₁H₁₁] can be transformed into A₂[B₁₁H₁₁] with the corresponding ammonium chlorides in aqueous solution (A = [NMe₃Ph], [NBzlEt₃], [N(PPh₃)₂]). The crystal structure analysis of [Li(thp)₃]₂[B₁₁H₁₁] (space group P2₁/c) reveals a rather distorted octadecahedron for the [B₁₁H₁₁]^2– anion, whereas the corresponding octadecahedron in [NBzlEt₃]₂[B₁₁H₁₁] (space group P2₁2₁2₁) exhibits a structure close to C_2v symmetry, expected for the free anion. The protonation of [B₁₁H₁₁]^2– at low temperature gives [B₁₁H₁₂]^–, whose structure could be elucidated by NMR methods; it is formed, apparently, by the opening of the B1–B4 edge of [B₁₁H₁₁]^2– in the course of its known degenerate skeletal rearrangement, followed by the protonation of the B2–B4 edge. The reaction of [B₁₁H₁₂]^– with a second molecule of the acid HX (X = CF₃COO) gives nido-[B₁₁H₁₃X]^–. The addition of BH₃ to [B₁₁H₁₁]^2– yields closo-[B₁₂H₁₂]^2– under loss of H₂. Two [B₁₁H₁₁]^2– units are fused by the aid of FeCl₃, with the known anion [B₂₂H₂₂]^2– as the product, whose ¹¹B-NMR signals could completely be assigned on the basis of C_s symmetry. The compound [NBzlEt₃][N(PPh₃)₂][B₂₂H₂₂] crystallizes in the space group Pna2₁.     

Two Novel 1-D Organic–Inorganic Composite Phosphotungstates Constructed from [Ln(α-PW11O39)2]11− Units and [Cu(en)2]2+ Bridges (Ln = CeIII/ErIII)

Abstract  Two novel organic–inorganic composite phosphotungstates, [H₉{Ce(α-PW₁₁O₃₉)₂}Cu(en)₂] · 6H₂O (1) and H₇[Cu(en)₂{Er(α-PW₁₁O₃₉)₂}Cu(en)₂] · 12H₂O (2) (en = ethylenediamine) have been synthesized by the hydrothermal reaction of the trivacant Keggin polyoxoanion [α-A-PW₉O₃₄]⁹⁻ with Ce^III or Er^III ions in the presence of Cu²⁺ ions and en, and structurally characterized by IR spectra, elemental analysis and thermogravimetric analysis. X-ray crystallographic analyses indicate that they are all built by sandwich-type [Ln(α-PW₁₁O₃₉)₂]¹¹⁻ (Ln = Ce^III, Er^III) polyoxoanions and [Cu(en)₂]²⁺ cations generating infinite one-dimensional arrangements. To our knowledge, this 1-D chain structures constituted by mono-Ln sandwiched POM units and transition-metal complex cations are very rare. Graphical Abstract  Two novel organic–inorganic composite phosphotungstates, [H₉{Ce(α-PW₁₁O₃₉)₂}Cu(en)₂] · 6H₂O (1) and H₇[Cu(en)₂{Er(α-PW₁₁O₃₉)₂}Cu(en)₂] · 12H₂O (2) (en = ethylenediamine) have been synthesized by the hydrothermal reaction of the trivacant Keggin polyoxoanion [α-A-PW₉O₃₄]⁹⁻ with Ce^III or Er^III ions in the presence of Cu²⁺ ions and en, and structurally characterized by IR spectra, elemental analysis and thermogravimetric analysis. X-ray crystallographic analyses indicate that they are all built by sandwich-type [Ln(α-PW₁₁O₃₉)₂]¹¹⁻ (Ln = Ce^III, Er^III) polyoxoanions and [Cu(en)₂]²⁺ cations generating infinite one-dimensional arrangements. To our knowledge, this 1-D chain structures constituted by mono-Ln sandwiched POM units and transition-metal complex cations are very rare.      

Unprecedented High‐Nuclear Transition‐Metal‐Cluster‐Substituted Heteropolyoxoniobates: Synthesis by {V8} Ring Insertion into the POM Matrix and Antitumor Activities

Reactions of hexaniobate with vanadate in the presence of Ni²⁺, Zn²⁺, or Cu²⁺ have furnished three high‐nuclear vanadium cluster‐substituted heteropolyoxoniobates (HPNs): {Ni(en)₃}₅H{V^VNb₈V^IV₈O₄₄} ? 9 H₂O ( 1 ), (H₂en)Na₂[{Zn(en)₂(Hen)}{Zn(en)₂(H₂O)}₂{PNb₈V^IV₈O₄₄}] ? 11 H₂O ( 2 ), and Na{Cu(en)₂}₃{[Cu(en)₂]₂[PNb₈V^IV₈O₄₄]} ? 11 H₂O ( 3 ) (en=1,2‐diaminoethane). Their structures have been determined and characterized by single‐crystal X‐ray diffraction analysis, thermogravimetric analysis (TGA), and elemental analysis. Structural analysis has revealed that compounds 1 – 3 contain similar {V₈}‐substituted [X^VNb₈V^IV₈O₄₄]^11? (X=P, V) clusters, obtained by inserting a {V₈} ring into tetravacant HPN [XNb₈O₃₆]^27?. To the best of our knowledge, compounds 1 – 3 represent the first high‐nuclear vanadium cluster‐substituted HPNs, and compound 1 is the largest vanadoniobate cluster yet obtained in HPN chemistry. Nickel and zinc cations have been introduced into HPNs for the first time, which might promise a more diverse set of structures in this family. Antitumor studies have indicated that compounds 1 and 2 exhibit high activity against human gastric cancer SGC‐7901 cells, SC‐1680 cells, and MG‐63 cells.     

Darstellung, 11B-, 13C-, 1H-NMR- und Schwingungsspektren von Monoethoxyhydro-closo-Dodecaborat(2–) sowie Kristallstruktur von [(C5H5N)2CH2][B12H11(OC2H5)]

Preparation, ¹¹B, ¹³C, ¹H NMR and Vibrational Spectra of Monoethoxyhydro-closo-dodecaborate(2–), and the Crystal Structure of [(C₅H₅N)₂CH₂][B₁₂H₁₁(OC₂H₅)] By treatment of Na₂[B₁₂H₁₂] with dry HF in ethanol Na₂[B₁₂H₁₁(OC₂H₅)] is formed which has been separated by ion exchange chromatography on diethylaminoethyl(DEAE) cellulose from the starting compound and by-products. The X-ray structure determination of [(C₅H₅N)₂CH₂][B₁₂H₁₁(OC₂H₅)] (monoclinic, space group P2₁/m, a = 9.1906(3), b = 12.6612(8), c = 9.3640(12) Å, β = 112.947(6)°, Z = 2) reveals the complete ordering of the anion sublattice. The ¹¹B nmr spectrum exhibits the characteristic feature (1:5:5:1) of a mono substituted B₁₂ cage with a strong down-field shift of ipso-B at +6.5 ppm. In the ¹³C nmr spectrum a triplet at 67.9 ppm of the methylene group and a quartet at 19.5 ppm of the methyl group is observed. Correspondingly, the ¹H nmr spectrum shows two multiplets at 3.7 and 1.3 as expected for an ethoxy substituent, and a multiplet at 2.1 ppm due to the protons of the boron cluster. The i.r. and Raman spectra exhibit strong CH stretching vibrations between 2 963 and 2 863 cm^?1, and in the i.r. spectrum the CO and BO stretching frequencies of the B? O? C bridge are observed at 1 175 and 1 140 cm^?1.     

Synthesis and characterization of Schiff base metal complexes: their antimicrobial,genotoxicity and electrochemical properties

We have synthesized the three Schiff-base ligands H₂L¹–H₂L³ and their Co^II, Fe^III and Ru^III metal complexes. All compounds have been characterized by analytical and spectroscopic methods. Oxidation of cyclohexane has been done by the metal complexes in CH₃CN using H₂O₂ and/or t-butylhydroperoxide (TBHP) as a co-catalyst. The keto-enol tautomeric forms of the ligands have been studied in polar and non-polar organic solvents. Electrochemical properties of the complexes have been studied at different scan rates. Thermal studies were carried out for the compounds. The ligands H₂L¹–H₂L³ were mutagenic on Salmonella Typhimurium TA 98 strain in the presence and/or absence of S9 mix. While the ligands H₂L¹ and H₂L² showed mutagenic activity on the strain TA 100 with and without S9 mix, the ligand H₂L³ was not mutagenic for TA 100. Antimicrobial activity studies of the compounds have also been carried out.