Composés d'addition des halogénures de niobium(V) et de tantale(V): VI. Réactions d'échange des composés du chlorure de niobium(V) avec quelques nitriles

The ligand exchange reactions NbCl₅·?N + RCN* ? NbCl₅ · RCN* + RCN are studied by NMR. spectroscopy for R = Me₃C, Me, FCH₂, CICH₂, BrCH₂, ICH₂. The reaction is of zero order in RCN and of first order in NbCl₅ · RCN and thus a dissociative mechanism is suggested for all the ligands studied. The enthalpies and entropies of activation are determined over 50° to 90° temperature ranges. There is a linear correlation between ΔG≠ and the free enthalpy of formation of NbCl₅ RCN. However this correlation is shown to hold only for series of adducts having the same donor group.     

Composés d'addition des halogénures de niobium(V) et de tantale(V). V. Stabilité relative des composés des chlorures avec quelques oxydes et sulfures organiques

The adducts of niobium(V) and tantalum(V) chlorides with some aliphatic and cyclic oxides and sulfides, studied by NMR. spectroscopy in CHCl₃, are found to have 1:1 stoechiometry, at room temperature and lower. In the thioxane complex TaCl₅ · C₄H₈OS two species are present with the ligand coordinated by the sulfur atom or by the oxygen atom, respectively, in a proportion which has been determined. The thioxane adduct of niobium(V) chloride, however, is preferentially coordinated by the sulfur atom. There is also evidence for the species 2MCl₅ · C₄H₈OS. The relative basicity of each donor atom in dioxane, thioxane and dithiane is calculated and discussed. In contrast to the nitrile adducts, whose stability was found earlier to be controlled by inductive factors, the steric factors are more important for the ether and sulfide adducts: MCl₅ · Me₂X is more stable than the corresponding MCl₅ · Et₂X (M = Nb, Ta; X = O, S). Both niobium(V) and tantalum(V) chlorides have a soft behaviour, but NbCl₅ is a weaker Lewis acid than TaCl₅ and shows also a softer behaviour.     

Composés d'addition des halogénures de niobium(V) et de tantale(V) IV. Stabilité relative des composés de chlorures avec quelques nitriles

The relative stability constants of the adducts of MCl₅ (M ? Nb, Ta) with acetonitrile, halogenoacetonitriles, pivalonitrile, acrylonitrile and benzonitriles are determined in dilute solutions by NMR. methods. The stability of the adducts is controlled by inductive factors. Chemical shifts and analysis of the new compounds are reported.     

Composés d'addition des chlorures de terres rares avec le méthanol,l'éthanol et le propanol-2. Préparations,solubilités et réactions de transsolvatation

By reaction of hydrated rare earths chlorides (M = La, Nd, Sm, Gd, Dy, Er, Yb, Y) with orthoformates, the following adducts have been prepared: MCl₃· 4MeOH, MCl₃ ·3EtOH (M = La, Nd, Sm, Gd, Yb), MCl₄ · 4 EtOH (M = Dy, Er, Y); adducts MCl₃ · 3iso-PrOH have been prepared by successive action of methyl orthoformate and of 2-propanol. The solubilities of these adducts in the corresponding alcohols at 25° (for the lanthanum adducts equally at 0 and 50°) are given. Two examples of the transsolvatation of these compounds, yielding adducts with weakligands, are described.     

Reaktionsprodukte aus Chlormethoxiphosphinen und Antimon(V)-chlorid. Schwingungsspektren der 1:1 Addukte aus Methoxiphosphorylverbindungen und Antimon(V)-chlorid

Reaction Products of Chloromethoxiphosphines and Antimony (V) Chloride. Vibrational Spectra of the 1:1-adducts of Methoxiphosphoryl Compounds and Antimony (V) Chloride Chloromethoxiphosphines react with antimony(V) chloride in a redox process to yield the chloromethoxiphospllonium hexachloroantimonates(V) (CH₃O)₃PCl₂⁺SbCl₆^? (II) and CH₃OPCl₃⁺SbCl₆^? (III). II, III, (CH₃O)₃PCl⁺SbCl₆^?(1) and (CH₃O)₄P⁺SbCl₆^? eliminate easily methyl chloride and give the addition compounds OP(OCH₃)₃·SbCl₅(IV), OPCl(OCH₃)₂ · SbCl₅ (V), OPCl₂(OCH₃)·SbCl₅ (VI) and OPCl₃·SbCl₅ (VII). The vibrational spectra of IV, V nnd VI are discussed.     

Etude de composés d'addition d'acides de Lewis. XXXVI [1] Composés d'addition de l'anthraquinone-9, 10 et de l'anthrone avec divers acides de Lewis

Solid stoichiometric adducts of 9, 10-anthraquinone with SbCl₅, ZrCl₄, TiCl₄ SnCl₄, AlCl₃, have been prepared. The very important lowering Δω of the IR. carbonyl frequency, ranging from ?175 cm^?1 for SbCl₅ to ?117 cm^?1 for SnCl₄, shows that the acceptor is linked by a dative bond to the carbonyl oxygen atom acting as a donor; an assignment of most of the fundamental IR. frequencies is proposed for anthraquinone and the mentioned adducts. Similar assignments and interpretation have been made for anthrone and its solid adduct with SbCl₅, ZrCl₄, TiCl₄, SnCl₄, AlCl₃ and ZnCl₂, where the C?O lowerings range from ?164 cm^?1 for SbCl₅ to ?97 cm^?1 for ZnCl₂.     

Etude de composés d'addition d'acides de Lewis,XXXIV [1] Composés d'addition de benzoquinone-1, 4 avec TiCl4

The adduct 1,4-benzoquine · TiCl₄ has been prepared in CH₂Cl₂ solution at about ?60°. Its IR. spectrum has been recorded at the same temperature. The experimental study of the vibrational frequencies has been completed by the calculation of the fundamental vibrations in the molecular plane, using Wilson's FG method, with slightly simplified models of 1,4-benzoquinone · TiCl₄ (13 masses) and 1,4-benzoquinone · 2 TiCl₄ (14 masses); analysis by use of internal and symmetry coordinates. An assignment of most of the observed bands is proposed and the conclusion is reached that the complex, when solid, is (1,4-benzoquinone · TiCl₄)_n. The force constants F(C? O) are 9,85 · 10⁵ dyne/cm for the quinone and 8,8 · 10⁵ dyne/cm for the disturbed carbonyl bond of the polymerized complex in the model proposed. At ordinary temperature in benzene solution of the components the adduct 1,4-benzoquinone. TiCl₄ · benzene precipitated; with the help of the models, the fundamental vibrations of its IR. spectrum have been assigned.     

Structure electronique des complexes acide-base de Lewis. I. Structure electronique et conformation moléculaire des molécules F3P·BH3 et F2HP·BH3

The electronic structure and preferred conformations of F₃P·BH₃ and F₂HP·BH₃ are investigated in the framework of the CNDO /2 approximation. In complete agreement with microwave data, the staggered conformations are predicted to be the most stable ones. The barriers to internal rotation are in good agreement with experimental values (F₃P·BH₃: calc. = 3.03 kcal/mole, exp. = 3.24 ± 0.15 kcal/mole; F₂HP·BH₃: calc. = 3.63 kcal/mole, exp. = 4.05 ± 0.45 kcal/mole) and a bicentric energy partitioning shows that the variations of the total energy are completely reflected by the only variation of the interaction energy between phosphorus and H atoms bonded to boron. The analysis of the electron densities reveals the importance of the 3s(P) → 2p_x(B) transfer in the formation of the co-ordination. Finally, the computed dipole moment value and direction agree with corresponding experimental data.     

Adducts of niobium(V) and tantalum(V) halides. XIV. Structure and relative stability of the adducts with some phosphoryl compounds

The adducts of niobium(V) and tantalum(V) halides with some phosphoryl compounds have been studied in chloroform solution by ¹H- and ¹⁹F-FT-NMR. spectroscopy. These octahedral adducts of general formula MX₅ · L (M = Nb, Ta; X = F, Cl, Br; L = phosphoryl ligand) are monomeric and neutral. Their relative stability constants have been determined at ?60°. The stabilities are controlled by electronic effects of substituents on the phosphoryl group.     

Ionisation Chimique de Composés Aromatiques Nitrés

The collision induced dissociations of [MH – 30]⁺ ions observed in the chemical ionization (methane) mass spectra of some nitro aromatic compounds show that these ions are formed by reduction in the ion source with subsequent protonation and not by the previously reported losses of NO^· from the protonated molecular ions.     

Synthesis,characterization, and acceptor behavior of dichlorotris(2-t-butylphenoxo)niobium(V)

The reaction of niobium pentachloride with three equivalents of 2-t-butylphenol in carbon tetrachloride afforded [NbCl₂(OC₆H₄C(CH₃)₃-2)₃]. The identity of the complex has been established by elemental analyses, molar conductance, molecular weight determination, IR, ¹H, and ¹³C-NMR and UV-Vis spectral studies. Based upon these studies, a square–pyramidal geometry around niobium has been proposed. Thermal behavior of the complex has been studied by TGA and DTA. Acceptor behavior of [NbCl₂(OC₆H₄C(CH₃)₃-2)₃] toward Ph₃P, Ph₃As, Ph₃PO, Ph₃AsO, and an uncommon ligand arsenictrithiophenoxide As(SPh)₃ allows the isolation of 1 : 1 addition compounds as shown by physicochemical, IR, and ¹H-NMR spectral studies. The formation of [NbCl₂(OC₆H₄C(CH₃)₃-2)₃] · As(SPh)₃ appears to be the first adduct of its class and suggests the suitability of As(SPh)₃ as a ligand.     

Thermoanalytical investigations of niobium(V) chloride aryloxides

Niobium(V) chloride aryloxides [NbCl₃(OAr)₂] and [NbCl₂(OAr)₃] (Oar = —OC₆H₄Bu ^t -4 and —OC₆H₄OMe-4) have been prepared by reacting NbCl₅ with two and three equivalents of the respective phenol in CCl₄. The complexes have been characterized by elemental analysis, molecular weight determination, i.r., ¹H-n.m.r., u.v.–vis. and MS techniques. Thermal behaviour (t.g.–d.t.) of the complexes has also been studied and decomposition schemes proposed. The kinetic and thermodynamic parameters namely, the activation energy 'E ^*', the frequency factor 'A', entropy of activation 'S' and specific rate constant 'kr' etc. have been calculated employing the Coats–Redfern equation. The non-isothermal t.g. data has also been utilized to determine the most probable mechanism and corresponding activation energy for the decomposition of niobium(V) complexes by testing seven different theoretically possible decomposition mechanisms.     

Etude des composés d'addition des acides de LEWIS XXVII. Composés d'addition de la cyclohexanedione-1, 4 avec HgCl2, ZnCl2, et TiCl4

The adducts of cyclohexane-1,4-dione with HgCl₂, ZnCl₂, and TiCl₄ have been prepared, and the IR. absorption spectra of the solid products studied. The lowering of the carbonyl frequency shows that the acceptor is linked by dative bonds to the carbonyl oxygen donors. This result confirms the cyclohexane-1,4-dione · HgCl₂ structure which has been determined by X rays diffraction.     

Easily available niobium(V) mixed chloro‐alkoxide complexes as catalytic precursors for ethylene polymerization

The dinuclear [NbCl_n(OR)_(5‐n)]₂ (n = 4, R = Et, 1 ; n = 4, R = CH₂Ph, 2 ; n = 3, R = Et, 3 ; n = 2, R = Et, 4 ; n = 2, R = , 5 ), and [Nb(OEt)₅]₂, 6 , and the mononuclear niobium compounds NbCl₄[κ²? OCH₂CH(R′)OR] (R = Me, R′ = H, 7 ; R = Et, R′ = H, 8 ; R = CH₂Cl, R′ = H, 9 ; R = CH₂CH₂OMe, R′ = H, 10 ; R = R′ = Me, 11 ), NbBr₄[κ²? OCH₂CH₂OMe], 12 , and NbCl₃(κ²? OCH₂CH₂OMe)(κ¹? OCH₂CH₂OMe), 13 , were tested in ethylene polymerization. Optimized reaction conditions included the use of D‐MAO as co‐catalyst and chlorobenzene as solvent at 50 °C. Complex 7 , whose X‐Ray structure is described here for the first time, exhibited the highest activity ever reported for a niobium catalyst in alkene polymerization [151 kg_polymer × mol_Nb^?1 × h^?1 × bar^?1]. Compounds 1 , 3‐5 , 8 , 13 showed activities similar to that of 7 . Linear polyethylenes (characterized by FT‐IR, NMR, GPC, and DSC analyses) with a broad polydispersivity were obtained. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Adducts of Niobium (V) and Tantalum (V) Halides. XV. Ligand Exchange of the Adducts with Some Phosphoryl Compounds

The ligand exchange MX₅·L + *L?MX₅·*L + L for the octahedral adducts MX₅·L, in an inert solvent (CH₂Cl₂ or CHCl₃) with neutral ligands, proceeds via a dissociative D mechanism when M = Nb, X = Cl and L = phosphoryl compound. A dissociative interchange I_d mechanism is suggested when M = Nb or Ta, and X = F. A first order rate law and positive values for ΔS* (+4 to +14 cal K^?1 mol^?1) are observed for the exchanges on the pentachloride adducts. However, a second order rate law and large negative values for ΔS* (-15 to -24 cal K^?1 mol^?1) are found for the intermolecular neutral ligand exchange (measured by ¹H-NMR.) and for the intramolecular fluorine exchange (measured by ¹⁹F-NMR.) reactions on the pentafluoride adducts. The fluorine exchange is 2 to 5 times faster than the ligand exchange. The exchanges, on the pentachloride and on the pentafluoride adducts, are slowed down with increasing donor strength of the phosphoryl compound.     

Standard Molar Enthalpies of Formation of Ce(TCA)_3·3H_2O(s) and Ce(TCA)(C_9H_6NO)_2(s)

IntroductionBothrareearthions1and 8 hydroxyquinolineareofantibacterialfunction ,2 andtheircomplexeshavemorepowerfuldisinfection .Theirbinarycomplexeswerereport edasearlyasin 196 3.Atthesametime ,theresearchontheirternarycomplexeshavebecomeveryactiveinrecentyears,andtheyarewidelyappliedinmanyfields .3 6Dong6 reportedthesynthesisandcharacterizationofthecomplexesofrareearthtrichloroaceticacidsaltswith 8 hy droxyquinoline.Itsapplicationinleathermouldyproofshowedthatthecomplexeshavepowerfuldisinfe…     

Untersuchungen an Wasseraddukten des Antimon(V)-chlorids

Studies on Water Adducts of Antimony(V) Chloride Antimony(V) chloride gives four solid adducts of sbCl₅ · nH₂O I-IV (n = 1, 2, 3, 4) at room temperature. In the solid state I is oligomer by hydrogen bridges. In II, III, and IV are besides the adducts ionic products of the constitution H⁺(H₂O)_n] SbCl₅OH^? (n = 1, 2, 3). I and II reacts with sodium chloride to yield sodium hexachloroantimonate(V) · 1 resp. 2 H₂O. The vibrational spectra were discussed.     

Etude des composés d'addition des acides de Lewis - XXXV. Note sur les composés d'addition entre amides et,respectivement, PdCl2 et PtCl2

The adducts of dimethylformamide, diethylformamide, dimethylacetamide and diethylacetamide with PdCl₂ and PtCl₂ have been prepared and the IR. spectra of the compounds in nujol mull or in CH₂Cl · CH₂Cl solution are studied. The lowering of the carbonyl frequency (amide I) shows that the metal is linked by a dative bond to the amide oxygen atom acting as a donor; the lowering is about 33 to 59 cm^?1. The decrease of the frequency of the carbonyl group vibration, observed in these cases as for other addition compounds of Lewis acids, is due to an intramolecular electronic displacement in the direction of the amid oxygen atom.     

Kinetics of the reactions Br2 + HCN,BrCN + I−, S(CN)2 + I− in aqueous acid solution

Spectrophotometric methods have been used to obtain rate laws and rate parameters for the following reactions: with k_a, k_b, E_a, E_b having the values 85±5 l./mole · s, 5.7±0.2 s^?1 (both at 298.2°K), and 56±4 and 66±2 kJ/mole, respectively. with k_c=0.106±0.004 l./mole ·s at 298.2°K and E_c=67±2 kJ/mole. with k_d=(3.06 ±; 0.15) × 10^?3 l./mole ·s at 298.2°K and E_d=66±2 kJ/mole. Mechanisms for these reactions are discussed and compared with previous work.     

A long Nb=O double bond in bis(pyridinium) tetra­chlorooxo(pyridine‐κN)niobate(V) chloride

The asymmetric unit of the title compound, (C₅H₆N)₂[NbCl₄O(C₅H₅N)]Cl or (pyH)₂[O=NbCl₄(py)]Cl (py is pyridine), contains a discrete anionic niobium(V) complex, [O=NbCl₄(py)]⁻, and two protonated pyridine mol­ecules, which form medium–strong hydrogen bonds with the Cl⁻ counter‐ion. The Nb=O distance of 1.7643 (17) Å is the longest among those in congener niobium complexes reported to date. Extensive density functional theory studies of conformations of [O=NbCl₄(py)]⁻ and structural data mining raise doubts regarding the reliability of the length of this Nb=O double bond.