Jm. Arrieta

Total synthesis of decavanadates of organic bases. X-ray crystal structures of four decavanadates

Abstract Decavanadate solutions react with pyridine, 3-methylpyridine, 4-methylpyridine and 2-ethylpyridine to form orange-yellow or orange-red compounds: tetrakis(pyridinium)dihydrogen decavanadate [(C5H5NH)4(V10O28H2)] (A1); tetrakis(4-methylpyridinium)dihydrogen decavanadate dihydrate [(C6H7NH)4(V10O28H2)2H2O] (A2); tetrakis(2-ethylpyridinium)dihydrogen decavanadate [(C7H9NH)4(V10O28H2)] (A3); tetrakis(3-ethylpyridinium)dihydrogen decavanadate [(C7H9NH)4(V10O28H2)] (A4); hexakis(pyridinium)decavanadate [(C5H5NH)6(V10O28)] (B1); hexakis(3-methylpyridinium)decavanadate [(C6H7NH)6(V10O28)] (B2); and the hexakis(4-methylpyridinium)decavanadate [(C6H7NH)6(V10O28)] (B3). These compounds were characterized by elemental analysis, IR spectroscopy and thermogravimetric methods in the solid state and UV spectroscopy in solution. The X-ray crystal structures of A1, A2, A4 and B3 are also reported. Structural results confirm, in the solid state, the basicity sequence given by other authors, that could be related to the different capacity of charge redistribution of the distinct types of oxygen atoms on the surface of the polyanion.

Molybdates of aromatic heterocyclic compounds. Synthesis and structure of an octamolybdate containing coordinately bound pyrazole: [(C3H4N2)2(Mo8O26)]4−

Abstract Molybdenum trioxide reacts with pyrazole to give the octamolybdate: (C3H4N2H)4[(C3H4N2)2(Mo8O26)]. The anion [(C3H4N2)2(Mo8O26)]4−, is built of two C3H4N2MoO5 and six MoO6 edge-sharing octahedra. The MoNNC3H4 bond length is 2.243(4) A, giving a bond strength of 0.35.

Synthesis, spectroscopic and magnetic studies of cobalt(II), nickel(II) and copper(II) complexes with 3'- and 5'-methoxysalicylaldimine-3-ethylene-1H-indole. X-ray structure of bis(1H-indole-3-ethylene-5'-methoxysalicylaldimine) copper(II)

Abstract Two bidentate ligands and their cobalt(II), nickel(II) and copper(II) complexes are reported; these ligands were prepared by 1:1 Schiff base condensation of 3-(2-aminoethyl)indole (tryptamine, TPA) with salicylaldehyde derivatives. The structures of the compounds were assigned on the basis of IR, electronic, mass and tH NMR data. Bis(1H-indole-3-ethylene-5′-methoxysalicyIaldimine)copper(II), (C36H34N4O4Cu), crystallized in monoclinic space group P21/c and was subjected to a single-crystal X-ray structure analysis. The structure was solved by direct and Fourier methods, refined by full-matrix least-squares, and converged to a R value of 0.038 for 1358 observed reflections. The coordination of the copper(II) complex is trans-planar (CuO2N2) with Cu-O and Cu-N bond lengths of 1.88(1) A and 2.01(1) A, respectively. The magnetic susceptibilities of the two copper complexes show normal magnetic behaviour in the range 79–279 K. The coordination of the two nickel complexes is trans-planar (NiO2N2) and bo...

Thermogravimetric study of DMF loss from (C8H11NH)4W10O32·2DMF

The thermal behaviour of collidinium decatungstate with twoN,N-dimethylformamide (DMF) crystallization molecules was studied by thermogravimetry. The kinetic parameters for the first stage of the thermal decomposition were established from isothermal and nonisothermal mass-change studies. The chemical reaction in this step is the loss of DMF: as confirmed by1H NMR.The physical model of this reaction, nucleation-growth according to the Avrami-Erofeev law, withn=1/2, was found by comparison of the isothermal and non-isothermal TG data.ZusammenfassungDas thermische Verhalten von Collidinium-dekawolframat mit zweiN,N-Dimethylformamid-Molekülen (DMF) wurde thermogravimetrisch untersucht. Die kinetischen Parameter des ersten Schrittes der thermischen Zersetzung wurden aus isothermen und nicht-isothermen Massenveränderungen ermittelt. Die in diesem Schritt verlaufende Reaktion ist der Verlust von DMF gemäßwie durch1H-NMR bestätigt wurde. Das physikalische Modell dieser Reaktion, nämlich ein Keimwachstum entsprechend dem Avrami-Erofeev-Gesetz mitn=1/2, wurde durch Vergleich der isothermen und nicht-isothermen TG-Daten gefunden.РезюмеМетодом ТГ изучено те рмическое поведение аддукта соли коллиди ния с двумя молекулами диметилф ормамида (ДМФ). На основ е изотермических и неи зотермических измерений изменения веса определены кине тические параметры первой ста дии разложения этого аддукта. Спектрами ПМ Р было подтверждено, ч то на первой стадии разлож ения происходит потеря двух молекул д иметилформамида по с ледующей схеме: При сопоставлении да нных изотермической и неизотермической ТГ было найдено, что физическая модель эт ой реакции состоит в о бразовании центров кристаллиза ции и их роста и подчиняется закону А врами-Ерофеева сп=1/2.

Trans-chloro(3,4,5,6-tetrachloro-2-[(triphenylphosphine)aurio]phenyl)-bis(triphenylphosphine)platinum(ii)

C60H45AuCIsP3Pt, triclinic, Pi, a = 20.039 (3), b = 13.308 (2), c = 11.699(1)A, ~ = 67.27(1), fl = 96.67(1), ), = 103.27(1) °, V = 2799.4 (7) A 3, Z = 2, D c = 1.69 Mg m -3, ¢t = 5.68 mm -l. The positions of the Au and Pt atoms were determined by a Patterson synthesis, and those of the remaining non-H atoms using the DIRDIF program. The structure was refined by full-matrix least-squares methods to a final R = 0.035 for 6622 observed reflections. The Pt atom has a planar four-coordina- tion, with the triphenylphosphine groups in the trans position. The Au atom has a distorted linear coordina- tion due to steric effects between the phenyl groups.

Synthesis, characterization and thermogravimetric decomposition of 2-ethylpyridinium metatungstate monohydrate. Kinetic study of its thermal dehydration

Abstract2-Ethylpyridinium dodecatungstate(VI) monohydrate was synthetized and characterized asα-(C5H4NHC2H5)5H[H2W12O40] · H2O by chemical analysis and electronic, IR and1H NMR spectral studies.The UV spectra showed the characteristic maximum absorption at 260 nm for the metatungstate anion. The two central protons in the anion were also characterized via IR and1H NMR spectroscopy.The thermal behaviour of this compound was investigated by thermogravimetric and derivative thermogravimetric methods. The TG curves revealed four main steps of decomposition, viz. dehydration, partial organic base decomposition and pyrolysis of the organic base, leading to the formation of WO3 in the final stage.The intermediates obtained at the end of the various thermal decomposition steps were studied via the IR spectral data on the residues obtained by isothermal heating of the compound at different temperatures.Kinetic parameters for the dehydration reaction were obtained through two methods of analysis.Zusammenfassung2-Äthylpyridindodekawolframat(VI) monohydrat wurde hergestellt und durch chemische Analyse, Elektronenspektrum, IR und1HNMR Spektraluntersuchungen alsα-(C5H4NHC2H5)5H[H2W12O40] · H2O charakterisiert. Das UV Spektrum zeigte bei 260 nm ein für das Metawolframat Anion charakteristisches Absorptionsmaximum. Die zwei Zentralprotonen des Anions wurden auch durch IR und1HNMR Spektroskopie charakterisiert. Das thermische Verhalten dieser Verbindung wurde mittels TG und DTG untersucht. Die TG-Kurven zeigten vier Hauptzersetzungsschritte u. z. Dehydratisierung, partielle Zersetzung der organischen Base, · Pyrolyse der organischen Base und Bildung von WO3 als letzte Stufe. Die nach verschiedenen thermischen Zersetzungsschritten erhaltenen Zwischenprodukte wurden durch die Spektraldaten der Rückstände der isothermisch auf verschiedene Temperaturen erhitzten Verbindung untersucht. Die kinetischen Parameter der Dehydratisierung wurden nach zwei Analysenmethoden bestimmt.РезюмеМоногидрат 2-этилпиридинийдодек авольфрамата(VI) - α (C5H4NHC2H5)5H[H2W12O40] - был охарактеризован хим ическим анализом, электронными спектрами поглощени я, ИК- и ПМР спектрами, У Ф спектры показали наличие мак симума поглощения при 250 нм, ха рактерного для метавольфрамат-иона. Наличие в анионе двух основных протонов бы ло также подтвержден о ИК- и ЯМР спектроскопией. Терм ическое поведение этого соед инения было исследов ано методами ТГ и ДТГ. Кривые ТГ пока зали четыре основные стадии разл ожения: дегидратация, частичное разложение органиче ского основания и пиролиз органическо го основания, приводя щего к образованию трехоки си вольфрама на конечной стадии разл ожения. Промежуточны е продукты, образующиеся в конце каждой стадии разложения были изуч ены ИК спектроскопие й остатков, получаемых при изоте рмическом нагреве соединений п ри соответствующих т емпературах. Анализ данных, провед енный двумя методами, позволил оп ределить кинетическ ие параметры реакции дегидратаци и.

Kinetic study of the thermal dehydration of n-methylanilinium metatungstate dihydrate

N-Methylanilinium metatungstate dihydrate was synthetized from an aqueous solution at pH 5. Characterization was effected using polarography and UV, IR and 1H NMR spec- troscopy. The polarogram shows three characteristic peaks of the metatungstate anion and the UV spectrum shows an absorption maximum at 249 nm. The two central protons in the anion were characterized by IR and 1H NMR spectroscopy. Thermal dehydration was studied by isothermal and non-isothermal thermogravimetric measurements. Based on the isothermal data, the kinetic dependence kt = [−1n(1−α)]12 was found (where k is the rate constant, t reaction time and α the degree of conversion). The activation energy and frequency factor were found to be 156 kJ mol−1 and 8.6·1020 s−1, respectively, by the Satava [V. Satava, Thermochim. Acta, 2 (1971) 423] method and 143 kJ mol−1 and 4.57 · 1020 s−1 from isothermal measurements.

Investigation of the dehydration kinetics of 2-ethylpyridinium metatungstate monohydrate using a rising temperature technique

Abstract The differences in the kinetic equations used and the values of the apparent activation energy and frequency factor for the thermogravimetric dehydration of 2-ethylpyridinium metatungstate monohydrate have been obtained. Five different methods for the treatment of increasing temperature data have been attempted, taking into account 18 analytical forms of the f (α) or F (α) functions. One of these methods has been developed and checked for the first time in this work. The most probable mechanism is related to the F (α) expression, [-In(1−α)]. The E and A values obtained were 127–160 kJ mol −1 and 10 18 −4×10 21 s −1 respectively.

Synthesis, characterization and thermal behaviour of 2,6- and 3,4-dimethylpyridinium and 2,4,6-trimethylpyridinium octamolybdates

Abstract2,6- and 3,4-dimethylpyridinium and 2,4,6-trimethylpyridinium octamolybdates were synthesized and characterized and their thermal decompositions were studied by means of thermogravimetry. The thermal stabilities follow the sequence: 2,4,6-TMPO <2,6-DMPO <3,4-DMPO, which seems to be related to the positions of the methyl groups on the pyridine ring. Kinetic parameters were calculated for the first decomposition step of the two dimethylpyridinium octamolybdates. A nucleation mechanism is proposed. The best fit corresponds to a random nucleation (one nucleus per particle) controlled equation. The calculated activation energies were 120.9 and 133.7 kJ/mol−1 for the 2,6- and the 3,4 derivative, respectively.Zusammenfassung2,6- und 3,4-Dimethylpyridinium- und 2,4,6-Trimethylpyridinium-octamolybdate wurden synthetisiert, charakterisiert und hinsichtlich ihrer thermischen Zersetzung untersucht. Die in der Reihenfolge 2,4,6-TMP <2,6-DMP <3,4-DMP zunehmende thermische Stabilität scheint mit der Stellung der Methylgruppen im Pyridinring in Zusammenhang zu stehen. Die kinetischen Parameter wurden für den ersten Zersetzungsschritt der zwei Dimethylpyridinium-octamolybdate berechnet. Ein Keimbildungsmechanismus wird vorgeschlagen. Die beste Näherung ergibt eine Gleichung, die auf einer zufälligen Keimbildung mit einem Keim pro Partikel basiert. Für die Aktivierungsenergie der 2,6- und 3,4-Derivate wurden Werte von 120,9 bzw. 133,7 kJ/mol−1 berechnet.РезюмеМетодом ТГ изучено те рмическое разложени е синтезированных окт амолибдатов 2,6-3,4-димети л- и 2,4,6-триметилпиридиния. Термостойкость исследованных соеди нений располагается в ряд 2,4,6-триметилпирид иний < 2,6-диметилпиридиний < 3,4-д иметилпиридиний и связана с расположен ием метальных групп в пиридиновом кольце. О пределены кинетичес кие параметры первой ста дии разложения двух октамолибдатов диме тилпиридиния. Реакци я разложения лучше все го согласуется с меха низмом произвольного образ ования центров кристаллизации: на од ну частицу приходитс я один центр кристаллизации. Энер гии активации, вычисленные для 2,6-и 3,4-пр оизводных, составлял и, соответственно, 120,9и 133,7 кд ж·моль−1.

Structure of Hexakis(3-methylpyridinium) Decavanadate Bis(3-methylpyridinium Perchlorate) Dihydrate

[V10O28(C6H7NH)6].2(C6H7NH).2(ClO4).2-H2O, M(r) = 1945.4, monoclinic, P2(1)/c, a = 12.580 (2), b = 26.262 (5), c = 11.340 (4) angstrom, beta = 108.11 (2)-degrees, V = 3561 (2) angstrom3, Z = 2, D(m) = 1.8 (1) (by flotation in CHBr3-CCl4), D(x) = 1.81 Mg m-3, lambda(Mo Kalpha) = 0.71069 angstrom, mu=1.38 mm-1, F(000) = 1960, T = 298 K, R = 0.025 for 1789 observed reflections. The formula unit consists of the decavanadate anion, two perchlorate anions, eight 3-methylpyridinium cations and two water molecules and is centrosymmetric. The polyanion is similar to other known decavanadates. The perchlorate ions are disordered.