bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Oxidation of Gallium and Indium: Characterization of the Cyclic and Linear GaO2 and InO2 Molecules Generated by the Spontaneous and Photoinduced Reaction of Ga and In Atoms with O2 and Determination of the Reaction Mechanism
Authors: Köhn Andreas , Gaertner Benjamin , Himmel Hans‐Jörg 
Published: July 2005

AbstractIn this work, the spontaneous and photolytically activated reactions of Ga and In atoms (M) with O2 (in Ar and solid O2) are studied with the aid of the matrix‐isolation technique and the use of IR, Raman, and UV/Vis spectroscopy in combination with detailed quantum‐chemical calculations. Vibrational spectra were recorded for several different isotopomers (69Ga, 71Ga, 16O2, 18O2, 16O18O). The results show that the spontaneously formed cyclic MO2 molecules photoisomerize to give the linear OMO molecules. The collected vibrational data were then used to characterize the bond properties of the linear OMO molecules in detail. The results are compared to those obtained for CO2+ and neutral OEO compounds, where E is an element of Group 14. Quantum‐chemical calculations were carried out at various levels of theory for GaO2. These calculations indicate that linear OMO is slightly more stable than its cyclic isomer. These calculations were also used to obtain information about the reaction mechanism, and show that the formation of the cyclic isomer from Ga atoms and O2 occurs without a significant barrier. Abrupt changes of the dipole moment and the OO bond length during the approach of the O2 molecule toward the Ga atom mark the point on the potential energy surface at which one electron jumps from the Ga atom onto the O2 unit. The isomerization of cyclic GaO2 to the linear global minimum structure is accompanied by a significant barrier, which explains why this reaction requires photoactivation.
Chelation‐Controlled Radical Chain Reactions Studied by Electrospray Ionization Mass Spectrometry
Authors: Fürmeier Sven , Griep‐Raming Jens , Hayen Ahlke , Metzger Jürgen O. 
Published: July 2005

AbstractElectrospray ionization mass spectrometry (ESI‐MS) is a novel tool for the investigation of chemical reactions in solution and for the direct detection and identification of reactive intermediates. The tributyltin hydride mediated addition of tert‐butyl iodide to dimethyl 2‐cyclohexyl‐4‐methyleneglutarate (2) in the presence of Lewis acids was investigated by ESI‐MS using a microreactor coupled on‐line to an ESI mass spectrometer. For the first time we have been able to show that transient radicals in radical chain reactions can be detected unambiguously under steady‐state conditions in the reaction solution and can be characterized by ESI‐MS/MS and accurate mass determination. The detection of different heterodimer radical complexes by ESI‐MS/MS has provided new insights into the mechanism of Lewis acid controlled radical chain reactions. Dimeric chelate complexes of glutarates, such as 2 and 3, and Lewis acids, like Sc(OTf)3, MgBr2⋅OEt2 and LiClO4, were observed as well as higher aggregates with additional equivalents of Lewis acid. Evidence for a dynamic equilibrium of the complexes in solution was found by NMR spectroscopy. The ESI‐MS investigation of the chelation of glutarate 2 with various Lewis acids has led to the conclusion that the tendency for Lewis acids to form dimeric chelate complexes and higher aggregates has an important effect on the stereoselective outcome of the radical reactions.
Synthesis of a Dimeric Lewis Antigen and the Evaluation of the Epitope Specificity of Antibodies Elicited in Mice
Authors: Buskas Therese , Li Yanhong , Boons Geert‐Jan 
Published: July 2005

AbstractThe Lewisy–Lewisx heptasaccharide, modified by an artificial aminopropyl spacer, was synthesized by an approach that employed two orthogonally protected lactosamine building blocks. A p‐(benzoyl)‐benzyl glycoside was used as a novel anomeric protecting group, which could be selectively removed at a late stage in the synthesis, thus offering the benefit of enhanced flexibility. The artificial aminopropyl moiety was modified by a thioacetyl group, which allowed an efficient conjugation to keyhole limpet hemocyanin (KLH) that had been activated with electrophilic 3‐(bromoacetamido)‐propionyl groups. Mice were immunized with the LeyLex–BrAc–KLH antigen. Analysis of the sera by ELISA established that a strong helper T‐cell immune response was raised against the LeyLex saccharide. Further ELISA analysis showed that the titer for monomeric Ley tetrasaccharide was tenfold lower whereas recognition of the Lex trisaccharide was negligible.
Interaction of Ru(II) Complex with Yeast tRNA Studied by Isothermal Titration Calorimetry
Authors: Hong Xu , Jian‐Hong Liu , Zhi‐Gang Liu , Yi Liang , Peng Zhang , Fen Du , Bing‐Rui Zhou , Liang‐Nian Ji 
Published: July 2005

AbstractThe interaction of metal complex with RNA has been studied by isothermal titration calorimetry (ITC) for the first time. ITC experiments show that complex [Ru(phen)2MPIP]2+ {phen=1,10‐phenanthroline, MPIP=2‐(4‐methylphenyl)imidazo[4,5‐f]‐1,10‐phenanthroline} interacts with yeast tRNA in terms of a model for a single set of identical sites through intercalation, which is consistent with our previous observation obtained from spectroscopic methods, and this binding process was driven by a moderately favorable enthalpy decrease in combination with a moderately favorable entropy increase, suggesting that ITC is an effective method for deep studying the interactions of metal complexes with RNA.
Effect of Comonomer Ethylene on Plateau Modulus of Crystal‐line Ethylene‐propylene Random Copolymer with Broad Molecular Weight Distribution
Authors: Jian Ding , Ri‐Wei Xu , Xue‐Jia Ding , Ding‐Sheng Yu 
Published: July 2005

AbstractEthylene‐propylene random copolymer with ultra‐high molecular weight (UHPPR) and broad molecular weight distribution (MWD) was prepared with Ziegler‐Natta catalyst. The viscoelastic behavior of UHPPR has been investigated by means of oscillatory rheometer at 180, 200 and 220 °C. The loss modulus (G″ curves of 180 and 200 °C present a pronounced maximum at 38.10 and 84.70 r/s, respectively. For the first time, this makes it possible to directly determine the plateau modulus ($G^{0}_{N} $) of crystalline ethylene‐propylene random copolymer with broad MWD in a certain experimental temperature G″(ω) curve. The plateau modulus of UHPPR is 4.51×105 and 3.67×105 Pa at 180 and 200 °C respectively, increasing with random incorporation of comonomer ethylene into the molecular chains and being independent of molecular weight.
Synthesis, Characterization of Neutral Nickel Complexes Bearing N‐Fluorophenylsalicylaldimine Chelate Ligands and Their Catalytic Activity to Ethylene Oligomerization
Authors: Li‐Ping Song , Wei Zhao , Ji‐Ling Huang , Shi‐Zheng Zhu 
Published: July 2005

AbstractA series of neutral nickel complexes featuring N‐fluorophenylsalicylaldimine chelate ligands was synthesized, and the molecular structure of complex 4 was further confirmed by X‐ray crystallographic analysis. The neutral nickel complexes showed high activity up to 4.22×105 g oligomers/(mol Ni·h) and high selectivity to C6 olefins in catalyzing ethylene oligomerization using methylaluminoxane (MAO) as cocatalyst.
Preparation and Characterization of Novel Choline and L‐Glutamic Acid Mixed Monolayer Covalently Modified Glassy Carbon Electrode and Its Analytical Application to Nitrite Determination
Authors: Guan‐Ping Jin , Xiang‐Qin Lin 
Published: July 2005

AbstractA choline and L‐glutamic acid mixed monolayer covalently modified glassy carbon electrode (Ch‐Glu/GCE) was fabricated and characterized by X‐ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). It provided an excellent example of mixed covalent monolayer modification of carbon electrodes with alkanol and amino acid, and also a facile means for altering the interfacial architecture. The Ch‐Glu/GCE displayed good catalytic activity toward the oxidation of nitrite anions. Differential pulse voltammetry was used for determination of nitrite at the Ch‐Glu/GCE. The Ch‐Glu/GCE showed higher capability for restraint of pollutions than a simple Ch modified electrode or a simple Glu modified electrode.
Hydrolysis of p‐Nitrophenyl Picolinate Catalyzed by Mono‐ and Binuclear Transition Metal Complexes with Polyether Bridged Dihydroxamic Acid
Authors: Jian‐Zhang Li , Hong‐Bo Li , Fa‐Mei Feng , Jia‐Qing Xie , Shen‐Xin Li , Bo Zhou , Sheng‐Ying Qin 
Published: July 2005

AbstractTwo polyether bridged dihydroxamic acids and their mono‐ and binuclear manganese(II), zinc(II) complexes have been synthesized and employed as models to mimic hydrolase in catalytic hydrolysis of p‐nitrophenyl picolinate (PNPP). The reaction kinetics and the mechanism of hydrolysis of PNPP have been investigated. The kinetic mathematical model for PNPP cleaved by the complexes has been proposed. The effects of the different central metal ion, mono‐ and binuclear metal, the pseudo‐macrocyclic polyether constructed by polyethoxy group of the complexes, and reactive temperature on the rate for catalytic hydrolysis of PNPP have been examined. The results showed that the transition metal dihydroxamates exhibited high catalytic activity to the hydrolysis of PNPP, the catalytic activity of binuclear complexes was higher than that of mononuclear ones, and the pseudo‐macrocyclic polyether might synergetically activate H2O coordinated to metal ion with central metal ion together and promote the catalytic hydrolysis of PNPP.
Effect of Al2O3 on the Structure and Photoluminescence Properties of Sol‐gel Glass Doped with Rare Earth Organic Complex
Authors: Jing Xiao , Gui‐Jun Fu , Han‐Xing Liu , Shi‐Xi Ouyang 
Published: July 2005

AbstractBoth silica glass materials singly doped with rare earth organic complex and co‐doped with Al3+ were prepared by in situ sol‐gel method respectively. XRD and SEM measurements were performed to verify the non‐crystalline structure of the glass. The excitation spectra, emission spectra and IR spectra were measured to analyze the influence of the glass contents on the structure of the glass and the energy level of the doped Eu(III) ions. The effect of Al3+ on the photoluminescence properties of rare earth organic complex in silica glass was investigated. The IR spectra indicated that the in situ synthesized europium complex molecule was confined to the micropores of the host and the vibration of the ligands was frozen. When Al2O3 was doped into the silica host gel, the rare earth ions in the silica network were wrapped up and dispersed by Al2O3, so the distribution of Eu(III) complex in the host was more homogeneous, and the luminescence intensity of 5D0‐7F2 transition emission of the Eu3+ ions was improved. The results showed that an appropriate amount of Al3+ added to the gel glass improved the emission intensity of the complex in the silica glass, and when the content of Al2O3 reached 4 mol%, the maximum emission intensity could be obtained compared with that of other samples containing different Al2O3 contents.
Fully Accessible Ag Nanoparticles within Three‐dimensionally Ordered Macroporous SiO2
Authors: Quan‐Zhou Wu , Qiang Yin , Ju‐Fang Liao , Jing‐Heng Deng , Yu‐Guang Li 
Published: July 2005

AbstractA multi‐step process was used for preparation of three‐dimensionally ordered macroporous (3DOM) SiO2, in which fully accessible Ag nanoparticles are incorporated. The method involves the processes of assembly of polystyrene colloidal crystal, preparation of 3DOM SiO2, and incorporation of Ag nanoparticles within 3DOM SiO2 through in situ Tollens' reaction. XRD, SEM and EDXS determination show that the Ag particles deposited on the macroporous walls in nano dimension. The results indicate that lower concentration of silver ammoniate and formaldehyde in the solution is favorable for forming a very narrow size distribution and uniform shape of nanoparticles. However, the higher the concentration of the solution and the more the loading times, the larger the possibility to form un‐uniform particles. Ag nanoparticles can be sintered into larger and spheral particles by calcination at 600 °C, but can resist sintering owing to their high dispersivity when loading amount is small. The study provided a simple approach to tailor Ag/3DOM SiO2 composite materials with desired morphology and size of Ag particles within the macropores.
Electrical Properties and Dilatometric Measurements of La2Mo2O9under Low Oxygen Partial Pressure
Authors: Tian Xia , Jia‐Yan Li , Xin Luo , Qin Li , Jian Meng , Xue‐Qiang Cao 
Published: July 2005

AbstractThe electrical conductivity and thermal expansion of La2Mo2O9under low oxygen partial pressure were studied with the help of thermoelectric power and dilatometric measurements, respectively. The ionic conduction of La2Mo2O9was predominant with the electronic transference number less than 0.05 above an oxygen partial pressure of aboutp=10‐7Pa at 700°C, and below this pressure the electronic conduction became obvious. The defect reaction and small polaron hopping among molybdenum sites were proposed to explain the electronic conduction. Accompanying the phase transition, there was a sharp increase of thermal expansion, which became more serious under low oxygen partial pressure. The substitution of lanthanum by neodymium led to the increase of electrical conductivity but the decrease of phase stability.
Two Novel μ‐Oxo Diiron(III) Schiff Base Complexes: X‐ray Diffraction Analyses, IR, UV‐Vis, CD spectra, Magnetic Susceptibility and Electrochemistry
Authors: Wen‐Juan Ruan , Guo‐Hang Hu , Shu‐Jun Wang , Jian‐Hua Tian , Qing‐Lun Wang , Zhi‐Ang Zhu 
Published: July 2005

AbstractThe novel μ‐oxo diiron(III) Schiff base complexes, {[Fe(tbusalphn)]2(μ‐O)} (1) [tbusalphn = N,N′‐o‐pheny‐lenebis(3,5‐di‐tert‐butylsalicylideneiminato)] and {[Fe(R,R‐salchxn)]2(μ‐O)}(2) [R,R‐salchxn = N,N′‐R,R‐cyclo‐hexanebis(salicylideneiminato)] have been synthesized and characterized by elemental analyses, spectroscopy, magnetic susceptibility, electrochemical measurements and X‐ray diffraction techniques. X‐ray analyses revealed that the complex 1·CH3OH has nearly linear Fe‐O‐Fe angle of 176.5(2)° due to their steric crowding of ligands owing bulky substitute group, while fairly bent Fe‐O‐Fe angle was allowed by the reduced steric crowding of the ligands in 2·C4H6N2·0.5C2H5OH [149.6(1)°]. FT‐IR, UV‐Vis, CD spectra, magnetic susceptibility and cyclic voltammogram (CV) of complexes 1 and 2 have been further investigated.
Enthalpic Pair Interaction of Rubidium Chloride with α‐Amino Acid in Water at 298.15 K
Authors: Man‐Cheng Hu , Qian Yang , Yu‐Cheng Jiang , Shu‐Ping Xia 
Published: July 2005

AbstractThe mixing enthalpies of aqueous heavy rare alkali metal chloride RbCl solutions with aqueous α‐amino acid (L‐glycine, L‐alanine and α‐aminobutyric acid) solutions, as well as the dilution enthalpies of RbCl and α‐amino acid solutions in pure water had been measured at 298.15 K. The transfer enthalpies of RbCl from pure water to aqueous α‐amino acid solutions could be obtained from these data. The enthalpic pair interaction parameters of RbCl with α‐amino acid in water have been evaluated according to the McMillan‐Mayer theory and discussed in terms of the electrostatic interaction, structure interaction and Savage‐wood group additivity mode.
NaSO2Ph Induced Exclusive Isomerization of 1,2‐Allenyl Sulfoxides to 2‐Alkynylic Phenyl Sulfoxides
Authors: Chun‐Ling Fu , Sheng‐Ming Ma 
Published: July 2005

AbstractThe clean isomerization of 1,2‐allenyl sulfoxides in the presence of NaSO2Ph afforded 2‐alkynylic phenyl sulfoxides in good yields and selectivities. Although strong base‐catalyzed isomerization of allenes to alkynes is known, the mechanism for the current reaction is interesting for the obvious reason that NaSO2Ph is a weak base.
Study on the Reaction of Salicylic Acid with Dialkyl Phosphite by NMR and Electrospray Ionization Mass Spectrometry
Authors: Xiao‐Lan Chen , Ling‐Bo Qu , Lei Guo , Jian‐Sha Lu , Yan Liu , Jian‐Li Wu , Yu‐Fen Zhao 
Published: July 2005

AbstractThe reaction between salicylic acid and dialkyl phosphite was traced by electrospray ionization mass spectrometry and 31P NMR. All reactants, unstable intermediates and products were detected. The mechanism was proposed based on ESI‐MS results and 31P NMR profiles.
Crystal Structures of Two Calix[4]arene Isomers with Benzaldehyde Moiety and Their Photophysical Properties with Terbium(III) Ions
Authors: Hao Wang , Heng‐Yi Zhang , Yu Liu 
Published: July 2005

AbstractTwo calix[4]arene isomers with benzaldehyde moieties,i.e., 5,11,17,23‐tetra‐tert‐butyl‐25,27‐bis[2‐(o‐formyl‐phenoxy)ethoxy]‐26,28‐dihydroxycalix[4]arene (3) and 5,11,17,23‐tetra‐tert‐butyl‐25,27‐bis[2‐(p‐formylphenoxy)‐ ethoxy]‐26,28‐dihydroxycalix[4]arene (4), were synthesized according to a newly designed route in high yields, and their crystal structures have been determined by X‐ray crystallographic study. The photophysical behavior on com‐plexation of calix[4]arene derivatives3and4with terbium(III) nitrate was investigated in anhydrous acetonitrile at 25°C by UV‐Vis and fluorescence spectroscopies. The crystallographic structure of3indicated that the eight oxygen atoms formed a preorganized ionophoric cavity due to intramolecular π‐π stacking, which could encapsulate lanthanide ions tightly. In sharp contrast, the compound4formed a linear array by intermolecular π‐π stacking, hence the oxygen atoms of pendant arms could not coordinate with metal ions, giving a poor binding ability to Tb3+. The absorption spectra of3with Tb3+showed clearly a new broad intense absorption at 385 nm. Interestingly, the narrow emission line spectrum has also been observed for compound3with Tb3+, and the results obtained were discussed from the viewpoint of energy transfer mechanism between host structures and the properties of lanthanide ions.
Reaction of (Ph2N)2Sm(THF)4with Azobenzene: Synthesis, X‐ray Structure and Catalytic Behavior of [(Ph2N)(DME)Sm]2(μ‐η2:η2‐N2Ph2)2
Authors: Fu‐Gen Yuan , Xiu‐Juan Liu , Yong Zhang 
Published: July 2005

AbstractReaction of divalent (Ph2N)2Sm(THF)4with 1 equiv. of azobenzene in THF and then crystallization of the product in DME‐Et2O mixed solvent produced the complex of [(Ph2N)(DME)Sm]2(μ‐η2:η2‐N2Ph2)2(1) in 65.0% yield. In complex1, azobenzene molecules were reduced to be dianionic Ph2${\rm N}^{2-}_{2} $ligands, bridging two samarium ions in two η2:η2fashions. One samarium ion was bonded to a DME molecule and a diphenyl amido ligand besides two Ph2${\rm N}^{2-}_{2} $ligands. The unusual Ln‐η2‐arene close interaction was found for the first time for diphenyl amido lanthanides. Complex1could catalyze the polymerization of methyl methacrylate and acrylonitrile
Synthesis of New Triphenylene‐containing Discotic Liquid Crystals and the Influence of Fluorophilic Effect and Molecular Symmetry on Mesomorphism
Authors: Ke‐Qing Zhao , Bi‐Qin Wang , Ping Hu , Quan Li , Liang‐Fu Zhang 
Published: July 2005

AbstractNew symmetrical and asymmetrical triphenylene‐containing discotic liquid crystals with two different peripheral alkyl chains, known as sym‐TP(OC6H13)3(OR)3 and asym‐TP(OC6H13)3(OR)3, were synthesized. Their thermotropic liquid crystal properties were investigated through polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X‐ray diffraction (XRD) analyses. The asymmetrical discogens are 2,6,11‐trialkoxy‐3,7,10‐trihexyloxytriphenylenes, with the alkyl chain carbon numbers varying from 3‐10, 12, and 14, while the symmetrical compounds are 2,6,10‐trialkyloxy‐3,7,11‐trihexyloxytriphenylene. Two fluoroalkoxy substituted triphenylene discogens, 2,6,10‐tri(4,4,4‐trifluorobutoxy)‐3,7,11‐trihexyloxytriphenylene and its asymmetrical isomer 2,6,11‐tri(4,4,4‐trifluorobutoxy)‐3,7,10‐trihexyloxytriphenylene were prepared. These two compounds show higher melting and clearing points than their alkoxy analogs, which implies that fluorophilic effect exists in the formation and stabilization of discotic columnar mesophase. The triphenylene derivatives TP(OC6H13)3(OR)3 with two different peripheral chains, symmetrically or asymmetrically attached on triphenylene cores, have lower melting points and clearing points than those of the higher symmetrical compounds TP(OR)6 with the same total chain carbon numbers. The mixed‐chain‐triphenylenes with longer alkoxy chains (n=9, 10, 12, 14) show columnar mesophase at room temperature.
Interactions with ATP, DNA Cleavage and Anti‐tumor Activities of Complexes with Anions [Mo(V)O2(O2C6H4)2]3‐, [Mo(V)0.5W(VI)0.5O2(O2C6H4)2]2.5‐and [W(VI)O2(O2C6H4)2]2‐
Authors: Xiao‐Ming Lu , Ling Jiang , Xi‐An Mao , Chao‐Hui Ye , Jing‐Fen Lu , Jing‐Rong Cui 
Published: July 2005

Abstract(NH3CH2CH2NH2)3[Mo(V)O2(O2C6H4)2] (1), (NH3CH2CH2NH2)2.5[Mo(V)0.5W(VI)0.5O2(O2C6H4)2] (2) and (NH3CH2CH2NH2)2[W(VI)O2(O2C6H4)2] (3) were synthesized, structurally characterized by X‐ray diffraction analysis, and studied on their interactions with ATP, their DNA cleavage activities and antitumor properties. The redox state of molybdenum was not changed on going from crystal to aqueous solutions in complexes1and2, while tungsten underwent reduction from W(VI) to W(V) in complexes2and3. ATP promoted the oxidation of both molybdenum and tungsten from M(V) to M(VI) and the hydrolysis of catecholate ligands in solution consisting of ATP and the complexes. Complex1possesses fairly good activity to DNA cleavage and against tumor S180in mice, and is more effective than the control drug cyclophosphamide under the identical conditions. However, complexes2and3exhibited marginal effectiveness. The effectiveness of anti‐tumor of the complexes was related positively to their DNA cleavage activities and their hydrolysis of catecholate ligands.
Dinuclear Oxomolybdate(V) Species with Oxalato and Pyridine Ligands Revisited: cis/trans Isomerization of [Mo2O4(η2‐C2O4)2(R‐Py)2]2– (R‐Py = Pyridine, Alkyl‐Substituted Pyridine) in Water Evidenced by NMR Spectroscopy
Authors: Modec Barbara , Dolenc Darko , Brenčič Jurij V. , Koller Jože , Zubieta Jon 
Published: July 2005

AbstractThe simple oxohalomolybdate(V) ions [MoOCl4(H2O)]– and [MoOBr4]– were reacted with oxalic acid in mixtures containing an alcohol and a pyridine (R‐Py) to form the dinuclear anions [Mo2O4(η2‐C2O4)2(R‐Py)2]2– based on the {Mo2O4}2+ structural core. The dinuclear anion exists in two isomeric forms — as a trans and as a cis isomer. A trans arrangement of the pyridine ligands relative to the Mo2(μ2‐O)2 bridge was observed for (PyH)2[Mo2O4(η2‐C2O4)2Py2] (1), (PyH)2[Mo2O4(η2‐C2O4)2(3,5‐Lut)2] (2), [MeNC5H3(Me)2]2[Mo2O4(η2‐C2O4)2(3,5‐Lut)2]·H2O (3), (4‐MePyH)2[Mo2O4(η2‐C2O4)2(4‐MePy)2]·1/2(4‐MePy) (5), and [(C6H5)4P]2[Mo2O4(η2‐C2O4)2Py2]·H2O (7) [Py = pyridine; 3,5‐Lut = 3,5‐lutidine; MeNC5H3(Me)2+ = N‐methyl‐3,5‐lutidinium cation and 4‐MePy = 4‐methylpyridine], while a cis arrangement was found in only two compounds, namely (4‐EtPyH)2[Mo2O4(η2‐C2O4)2(4‐EtPy)2] (4) (4‐EtPy = 4‐ethylpyridine) and (4‐MePyH)3[Mo2O4(η2‐C2O4)2(4‐MePy)2]Br (6). The solution chemistry of the trans‐[Mo2O4(η2‐C2O4)2Py2]2– anion was monitored by 1H and 13C variable temperature NMR spectroscopy and showed evidence of two processes: the substitution of a pyridine ligand for water, coupled with cis/trans isomerization. Both reactions were exploited in the preparation of trans‐(PyH)2[Mo2O4(η2‐C2O4)2(H2O)2] (8) from a water/methanol solution of cis‐(4‐EtPyH)2[Mo2O4(η2‐C2O4)2(4‐EtPy)2] (4). trans‐(PyH)2[Mo2O4(η2‐C2O4)2(H2O)2] (8) was seen to react with methanol with the rupture of the molybdenum‐to‐oxalate bonds resulting in the cyclic octanuclear anion which crystallizes as a pyridinium salt, (PyH)2[Mo8O16(OCH3)8(μ8‐C2O4)]·2CH3OH (9). The compounds were fully characterized by X‐ray structural analysis and IR spectroscopy. MO calculations were performed on the isomeric pair of [Mo2O4(η2‐C2O4)2(4‐MePy)2]2– in order to establish their relative energies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)