NMR study of the propagation center in cationic polymerization of N-benzoyl-8-octanelactam. I. The structure of model living oligomers

Model living oligomers of N-benzoyl-8-octanelactam initiated by the model octanoylium hexachloroantimonate, SbCl₅, and by Ph₃C⁺ AsF₆^?, were studied by ¹H and ¹³C one- and two-dimensional nuclear magnetic resonance using the COSY, S-INEPT, COLOC, and ROESY methods. If prepared in the more solvating mixture of 1,1,2,2-tetrachloroethane (TCE) with 1,2-dichlorobenzene, the oligomers were found to be linear with the acylium ion as a living group on one end; in TCE only, the oligomers are highly branched. In both cases, the propagation center appears to be strongly coordinated to the nearest benzoylamide chain group. © 1993 John Wiley & Sons, Inc.     

Dark‐cure studies of cationic photopolymerizations of epoxides: Characterization of the active center lifetime and kinetic rate constants

We have characterized the effective rate constants for termination/trapping (k_t/t) and propagation (k_p) for solvent‐free cationic photopolymerizations of phenyl glycidyl ether for conversions up to 50%. We have performed dark‐cure experiments in which active centers are produced photochemically for a specified period of time until the initiating light is shuttered off, and then the polymerization rate is monitored in the dark. This method is especially well suited for characterizing cationic polymerizations because of the long active center lifetimes. Our analysis provides profiles of the instantaneous kinetic rate constants as functions of conversion (or time). For photopolymerizations of phenyl glycidyl ether initiated with iodonium photoinitiators, k_t/t and k_p remain essentially invariant for conversions up to 50%. For the photoinitiator (tolycumyl) iodonium tetrakis (pentafluorophenyl) borate (IPB), the values of k_t/t at 50 and 60 °C are 0.027 and 0.033 min^?1, respectively. The corresponding values of k_t/t for diaryliodonium hexafluoroantimonate (IHA) are 0.041 and 0.068 min^?1. The values of k_p at 50 °C for IPB and IHA are 0.6 and 0.4 L mol^?1 s^?1, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2064–2072, 2003     

Cationic Copolymerization of Propylene Oxide with Tetrahydrofuran. XI. Calculation of Individual Rate Constants

Rate constants (k₁ k₁₁, k₁₂, k₂₂, k₂₁ and k_t) for various steps involved in the copolymerization of propylene oxide (PO) with tetrahydrofuran (THF) have been calculated from reaction rate data obtained with the following catalyst system: (a) triphenyl-methyl cations ((C₆H₅)₃C⁺) associated with hexafluorophosphate (PF₆ ^?), hexafluoroarsenate (AsF₆ ^?) and hexafluoroantimonate (SbF₆ ^?) gegenions; (b) antimony pentachloride (SbCl₅); and, (c) boron trifluoride etherate, BF₃:(C₂H₅)₂O. The latter two systems were studied in the presence of cocatalysts. The effects of several parameters (the cocatalyst concentration and bulk size, the nature of the solvent, and the reaction temperature) on the rate constants are highlighted. The role of entropy in the initiation, propagation and termination steps is discussed in terms of solvation and desolvation processes. Based on termination activation energy considerations, the order of stability for the gegenions used in the copolymerization of PO with THF was found to be: AsF₆ ^? > SbF₆ ^? > HOBF₃ ^?PF₆ ^? > SbCl₆ ^?     

Acidité dans le nitrométhane: IV. Étude électrochimique des complexes chlorures de l'antimoine(III et V). HSbCl6

The electrochemical behavior of SbCl₃ and SbCl₅ is studied in nitromethane. SbCl₃ and SbCl₅ are Cl^? acceptors, giving respectively SbCl₄/^? (log K formation=4), and SbCl₆ (log K formation=15). Formal potentials of systems are determined. SbCl₅ reacts with HCl, giving the solvated proton H_S/⁺ and SbCl₆/^?; it is not possible to determine the formal potential of the hydrogen electrode, using HSbCl₆ as an acid, because the reduction of Sb^v occurs before the reduction of H_S/⁺.     

Pulsed laser polymerization study of the propagation kinetics of acrylamide in water

Pulsed laser polymerization was used in conjunction with aqueous‐phase size exclusion chromatography with multi‐angle laser light scattering detection to determine the propagation rate coefficient (k_p) for the water‐soluble monomer acrylamide. The influence of the monomer concentration was investigated from 0.3 to 2.8 M, and k_p decreased with increasing monomer concentration. These data and data for acrylic acid in water were consistent with this decrease being caused by the depletion of the monomer concentration by dimer formation in water. Two photoinitiators, uranyl nitrate and 2,2′‐azobis(2‐amidinopropane) (V‐50), were used; k_p was dependent on their concentrations. The concentration dependence of k_p was ascribed to a combination of solvent effects arising from association (thermodynamic effects) and changes in the free energy of activation (effects of the solvent on the structure of the reactant and transition state). Arrhenius parameters for k_p (M^?1 s^?1) = 10^7.2 exp(?13.4 kJ mol^?1/RT) and k_p (M^?1 s^?1) = 10^7.1 exp(?12.9 kJ mol^?1/RT) were obtained for 0.002 M uranyl nitrate and V‐50, respectively, with a monomer concentration of 0.32 M. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1357–1368, 2005     

Solutions of nylon-6 in antimony trichloride

Dilute solution viscosity measurements of nylon-6 in molten SbCl₃ reveal a polyelectrolyte effect that becomes more pronounced with increased molecular weight of the polymer sample. Intrinisic viscosities result in a relationship of [η] = 2.35 × 10^?6M^1.45_w for nylon-6 in SbCl₃ at 100°C, which indicates a high polymeric chain extension in molten SbCl₃ in the limit of zero concentration. Infrared (IR) and nuclear magnetic resonance (NMR) spectra indicate that a substantial fraction of the amide groups in each polymer chain remains unaffected, whereas the rest is interacted, probably, with SbCl₄-ions originating from the self-ionization of SbCl₃.     

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.     

Über die Darstellung der Trimercaptosulfoniumsalze [S(SH)3]+AsF6− und [S(SH)3]+SbCl6−

Preparation of Trimercaptosulfonium Salts [S(SH)₃]⁺AsF₆^? and [S(SH)₃]⁺SbCl₆^? The preparation of the trimercaptosulfonium salts [S(SH)₃]⁺AsF₆^? and [S(SH)₃]⁺SbCl₆^? from SCl₃⁺ salts with excessive H₂S at 193 K is reported. The [S(SH)₃]⁺SbCl₆^? is transferred into [S(SCl)₃]⁺SbCl₆^? by reaction with Cl₂ at low temperatures. The new [S(SH)₃]⁺ cation is isoelectronic to P(PH₂)₃. In addition, its existence is supported by an ab-initio calculation. The results show a potential well for C_3v configuration with SH bonds bended towards the top of the pyramid for the isolated ion. Also the results of a force-field calculation are reported.     

NQR-Untersuchungen an Addukten des SbCl3 und SbCl5. 35Cl- und 121,123Sb-NQR-spektroskopische Untersuchungen der Wechselwirkung zwischen SbCl3 bzw. SbCl5 und Phosphoryl- sowie Thiophosphorylchloriden

NQR Studies on Adducts of SbCl₃ and SbCl₅. ³⁵Cl- and ^121,123Sb-NQR Spectroscopic Studies of the Interaction between SbCl₃ or SbCl₅ and Phosphoryl or Thiophosphoryl Chlorides The complex formation between SbCl₃ and SbCl₅, respectively, and the chlorides POCl₃, P₂O₃Cl₄, and P₂OS₂Cl₄ has been studied by NQR spectroscopy. The formation of the adducts SbCl₃ · 2 POCl₃ and SbCl₅ · P₂OS₂Cl₄ has been proved. Based on its ³⁵Cl-NQR spectrum for the latter compound the constitution of a hexachloro antimonate P₂OS₂Cl₃⁺SbCl₆^? is assumed.     

Schwingungsspektroskopische Untersuchungen an Trimethylphosphonium-Kationen (CH3)3PX+ (X = H,D) und Kristallstrukturen von (CH3)3PD+SbCl6− und (CH3)3PCl+SbCl6−

Vibrational Spectra of Trimethylphosphonium Cations (CH₃)₃PX⁺ (X = H, D) and Crystal Structures of (CH₃)₃PD⁺SbCl₆^? and (CH₃)₃PCl⁺SbCl₆^? The trimethylphosphonium salts (CH₃)₃PX⁺SbCl₆^? (X = H, D) and (CH₃)₃PH⁺MF₆^? (M = As, Sb) are prepared and characterized by vibrational and NMR spectroscopy (¹H, ³¹P, ¹³C). In addition the crystal structures of (CH₃)₃PD⁺SbCl₆^? and (CH₃)₃PCl⁺SbCl₆^? are reported. (CH₃)₃PD⁺SbCl₆^? crystallizes in the orthorhombic space group Pnma with a = 1555(1) pm, b = 753.1(8) pm, c = 1166(1) pm Z = 4. (CH₃)₃PCl⁺SbCl₆^? crystallizes triclinic in the space group P1 with a = 704.6(4) pm, b = 729.5(3) pm, c = 1391.1(7) pm, α = 89.57(4)°, b? = 88.04(4)°, γ = 74.98(4)° and Z = 2.     

Über die Darstellung von Dimethyl(mercapto)sulfonium-hexa-chloroantimonat [(CH3)2SSH]+SbCl6−

Preparation of Dimethyl(mercapto)sulfonium-hexachloroantimonate [(CH₃)₂SSH]⁺SbCl₆^? The preparation of [(CH₃)₂SSH]⁺SbCl₆^? from [(Ch₃)₂SCl]⁺SbCl₆^? and H₂S at 223 K is reported. This salt is stable below 243 K and is characterized by vibrational spectroscopy.     

Ethers as ligands. Part VI. Transition metal(II) complexes with 18-crown-6

Summary Seven new coordination compounds are reported with the cyclicpolyether 18-crown-6 as the ligand,viz. [Mg(18-crown-6) (H₂O)₂](SbCl₆)₂, [M(18-crown-6)(MeNO₆)₂](SbCl₆)₂ with M is Ca²⁺ and Sr²⁺, [M(18-crown-6)(MeNO₂)](SbCl₆)₂ with M is Mn²⁺ and Co²⁺, and [M(18-crown-6)](SbCl₆)₂ with M is Ni²⁺ and Zn²⁺.     

A calorimetric study of the interaction of H2O·SbCl5 and HCl-SbCl,with weak organic bases in 1,2-dichloroethane

The enthalpies of interaction between H₂O·SbCl₅ and the oxygen bases DMA, n-Pr₂O, MePrCO, and EtOAc to form ternary complexes D·H₂O-SbCl₅ in 1,2-dichloroethane solution have been determined calorimetrically. Reaction of water with the binary adducts D·SbCl₅;, result in the formation of the same ternary complexes which has been confirmed by PMR spectroscopic experiments. The base molecules are considered to be strongly H-bonded to the H₂O-SbCl₅ adduct in the complexes in solution.The enthalpy of formation of H₂O-SbCl₅ in 1,2-dichloroethane solution has been redetermined.The enthalpies of formation of the [DH]⁺SbCl^?₆ and [D₂H]+SbCl^?₆ complexes from the complex acid HCl-SbCl₅ and Pr₂O, MePrCO and (MeO)₂CO have been determined and estimates of the association constant for the formation of the [DH]⁺SbCl^?₆ complexes from the D·SbCl₅, adducts have been derived for D = MePrCO, EtOAc and (MeOP₂CO.Measurements of the interaction between HCl-SbCl₅ and the protogenic ligands PrOH and H₂O were also made.     

Heterogeneous Ziegler‐Natta Catalyst Based on Neodymium for the Stereospecific Polymerization of Butadiene

The synthesis of a series of neodymium complexes supported on modified silica is reported. In an initial step the silanol groups were masked by a Lewis acid (BCl₃, AlCl₃, TiCl₄, ZrCl₄, SnCl₄, SbCl₅, HfCl₄), and then a soluble arene complex Nd(η⁶‐C₆H₅Me)(AlCl₄)₃ formed in situ was reacted with the modified silica. The supported complexes are active and highly stereospecific for butadiene polymerization; 1,4‐cis insertion is superior by 99%. The catalyst based on a treatment of silica with BCl₃ is the most efficient.     

The initiation process in the polymerization of tetrahydrofuran with carbonium ion salts

The initiation process for the polymerization of tetrahydrofuran with (C₆H₅)₃C⁺SbCl₆^? has been studied. Two mechanisms have been considered: a cation-addition process, and a process in which tetrahydrofuran donates a hydride ion to the cation of the initiator to form triphenylmethane. The biscarbonium salt [(C₆H₅)₂C⁺C₆H₄CH₂]₂(SbCl₆^?)₂ has been synthesized and used to initiate the polymerization of tetrahydrofuran. The results are consistent with the hydride-ion mechanism but may be inconclusive because of chain transfer. NMR experiments with 0.05–0.2M solutions of initiator in tetrahydrofuran show that triphenylmethane is rapidly produced in an amount equal to the molar amount of initiator originally present. Some NMR evidence for the presence of an acetal end group in the polymer has been obtained. It is concluded that the initiation process in this system definitely involves the formation of triphenylmethane, although a detailed, unique mechanism cannot be selected at this time.     

Effect of the Counterion on the Cationic Polymerization Rate of Ethylene Oxide by Trityl Salts

The cationic polymerization of ethylene oxide by trityl salts (BF₄ ^?, SbCl₆ ^?, AsF₆ ^?, and PF₆ ^? as counterions) in nitrobenzene at different temperatures has been studied. The kinetic analysis was carried out by use of an automatic manometer, and it showed that the polymerization rate constant depends neither on the counterion type nor on the initial initiator concentration. These facts allowed us to conclude that macrocations and macroion pairs have the same reactivity.     

Synthese,Kristallstruktur und 121Sb-Mößbauer-Spektrum von [SbCl2(18-Krone-6)]+SbCl6−

Synthesis, Crystal Structure, and ¹²Sb-Mössbauer Spectrum of [SbCl₂(18-Crown-6)]⁺SbCl₆^? The title compound, which has been prepared by the reaction of antimony trichloride and antimony pentachloride in the presence of 18-crown-6 in acetonitrile solution, is characterized by its ¹²¹Sb-Mössbauer spectrum and by an X-ray structure determination. Space group P2₁, Z = 2, 2439 observed unique reflections, R = 0.045, wR = 0.043. Lattice dimensions at ?80°C: a = 780.6(7), b = 1297.5(9), c = 1 278.5(10) pm, β = 100.56(7)°. The structure of [SbCl₂(18-crown-6)]⁺SbCl₆^? contains cations in which the antimony atom in the first coordination sphere is surrounded in a ?-trigonal-bipyramidal fashion by two oxygen atoms of the crown ether in axial position as well as in the equatorial position by the two chlorine atoms and the lone electron pair.     

Mechanism of Polymerization of 1, 3-Dioxolane Initiated by (C2H5)3 O+SbCl6 and SbCl5

The kinetics of polymerization of 1, 3-dioxolane (DiOX) initiated by (C₂H₅)₃O⁺SbCl₆ and SbCl₅ has been studied and the elementary stages of the process have been considered. The polymerization of DiOX by (C₂H₅)₃O⁺SbCl₆-is shown to proceed at a steady rate to high conversion. A constant concentration of active centers in the system is maintained due to the equal rates of decomposition of active centers and disproportionation. The nonsteady-state character of DiOX polymerization initiated by SbCl₅is associated with a relatively lower stability of the counter-ion SbCl₅ OR^? compared with SbCl₆. The initiation of DiOX polymerization by (C₂H₅)₃O⁺SbCl₆ proceeds without hydride-transfer reactions, and the concentration of active centers in the system is determined not by processes taking place in the initiation stage, but by the existence of a definite kind of equilibrium with the participation of active centers.     

Estimation of activation parameters for the propagation rate constant of styrene

For a temperature range of −11.8–92.6°C, the propagation rate constant k_p of styrene has been determined with the use of pulsed-laser polymerization (PLP). The temperature dependency of the obtained k_p data was evaluated using the Arrhenius equation. The NLLS error-in-variables method (EVM) is recommended for this fit. The resulting activation energy is 32.6 kJ mol⁻¹ and the pre-exponential factor is 10^7.66 dm³ mol⁻¹ s⁻¹. A joint confidence interval for these parameters is given. © 1996 John Wiley & Sons, Inc.     

The reactions of polyacetylene with trimethyloxonium hexachloroantimonate. Covalent doping of (CH)x

Polyacetylene, (CH)_x, has been doped with trimethyloxonium hexachloroantimonate, (CH₃)₃O⁺SbCl(1), in dichloromethane and acetonitrile. The maximally doped (CH)_x films have moderate conductivities [σ_RT(CH₂Cl₂) = 10, σ_RT(CH₃CN) = 0.7 Ω^?1 cm^?1]. Reactions between 1 and (CH)_x CH₂Cl₂ or CH₃CN were followed in situ by ¹H nuclear magnetic resonance spectroscopy and x-band electron spin resonance spectroscopy. It was found that the reactions in the two solvents are different. In dichloromethane the dopant is SbCl₅, which forms from the decomposition of 1, and doping proceeds by electron removal from (CH)_x chains. Based on the ESR signal loss, an estimate can be made of the diffusion rate of SbCl₅, into the (CH)_x fibrils in CH₂Cl₂; it is found to be ca. 10^?17 cm²/s. In acetonitrile the dopant appears to be either CH₃CNCH, H⁺, CH, or a combination of one or more of these dopants. It is postulated that the CH₃CNCH, CH, and/or H⁺ dopant covalently binds to the (CH)_x chain. X-ray photoelectron spectra show that films doped with excess 1 in both solvents have approximately one SbCl per 33 CH units.