Regiospecific synthesis of 2-allyl-1,2,3-triazoles by palladium-catalyzed 1,3-dipolar cycloaddition

2-Allyl-1,2,3-triazoles were prepared by the palladium-catalyzed three component coupling (TCC) reaction of alkynes, allyl methyl carbonate and trimethylsilyl azide. A π-allylpalladium azide complex, which undergoes the 1,3-dipolar cycloaddition with alkynes, is proposed as a key intermediate in the TCC reaction.     

Synthesis of allyl cyanamides and N-cyanoindoles via the palladium-catalyzed three-component coupling reaction

The palladium-catalyzed three-component coupling reaction (TCCR) of aryl isocyanides, allyl methyl carbonate, and trimethylsilyl azide was conducted in the presence of Pd(2)(dba)(3).CHCl(3) (2.5 mol %) and dppe (1,2-bis(diphenylphosphino)ethane) (10 mol %). Allyl aryl cyanamides with a wide variety of functional groups were obtained in excellent yields. This palladium-catalyzed TCCR was further utilized for the synthesis of N-cyanoindoles. The reaction of 2-alkynylisocyanobenzenes, allyl methyl carbonate, and trimethylsilyl azide in the presence of Pd(2)(dba)(3).CHCl(3) (2.5 mol %) and tri(2-furyl)phosphine (10 mol %) at higher temperatures afforded N-cyanoindoles in good to allowable yields. (eta(3)-Allyl)(eta(3)-cyanamido)palladium complex, an analogue of the bis-pi-allylpalladium complex, is a key intermediate in the TCCR, and a pi-allylpalladium mimic of the Curtius rearrangement is involved to generate the (eta(3)-allyl)(eta(3)-cyanamido)palladium intermediate.     

A one-pot procedure for the regiocontrolled synthesis of allyltriazoles via the Pd-Cu bimetallic catalyzed three-component coupling reaction of nonactivated terminal alkynes, allyl carbonate, and trimethylsilyl azide

A one-pot procedure for the regiocontrolled synthesis of both 2-allyl- and 1-allyl-1,2,3-triazoles via the three-component coupling (TCC) reaction between nonactivated terminal alkynes, allyl carbonate, and trimethylsilyl azide (TMSN(3)) under a palladium and copper bimetallic catalyst has been developed. To accomplish the regioselective synthesis of the allyltriazoles, proper choice of two different catalyst systems is needed. The combination of Pd(2)(dba)(3).CHCl(3)-CuCl(PPh(3))(3)-P(OPh)(3) catalyzes the formation of 2-allyl-1,2,3-triazoles, while the combination of Pd(OAc)(2)-CuBr(2)-PPh(3) promotes the formation of 1-allyl-1,2,3-triazoles. The cooperative activity of palladium and copper catalysts plays an important role in the present transformations. Most probably, the palladium catalyst works as a catalyst for generating reactive azide species, pi-allylpalladium azide complex and allyl azide. The copper catalyst probably behaves as an activator of the C-C triple bond of the starting terminal alkynes by forming a copper-acetylide intermediate and thereby promotes the [3 + 2]-cycloaddition reaction between the reactive azide species and the copper-acetylide to form the triazole framework.     

Iron(II)-catalyzed sulfimidation and [2,3]-sigmatropic rearrangement of propargyl sulfides with tert-butoxycarbonyl azide. Access to N-allenylsulfenimides

The iron(II)-catalyzed Bach reaction of tert-butoxycarbonyl azide (BocN(3)) and allyl sulfides has been extended to include propargyl sulfides, which give N-allenylsulfenimide products. Using 10 mol % dppeFeCl(2) as catalyst the reaction proceeds at 0 degrees C with a number of different propargyl sulfides in 31-73% isolated yield. The reaction is limited by product instability toward catalyst and termination of the catalytic cycle by excess BocN(3). N-Allenylsulfenimide 2b smoothly undergoes catalytic hydrogenation and a Diels-Alder reaction with cyclopentadiene.     

低熔点晶体叠氮二乙基铝的合成和证明

叠氮二乙基铝（DEAA)是叠氮有机铝化合物中比较重要的一个化合物,但对DEAA的合成报道很少,还没有分离出纯的DEAA的报道。对它的研究有着重要的理论意义和应用价值。DEAA用作叠氮化试剂可用于多种叠氮化反应^[1-3];作为MOCVD前体物,由DEAA可制得性能优良的纳米级AIN材料,如AIN微晶薄膜^[4-6]和AIN粉末材料;DEAA是高含能材料,在国防和空间技术领域有着潜在的应用前景。文献报道的DEAA的合成方法按原料可分为三种^[7-10],其中以叠氮化钠和氯化二乙基铝（DEAC）为原料的合成方法应用较广,得到的DEAA为无色透明液体,熔点为－130℃^[11]。但笔者曾和到过固体DEAA^[12]。因此,本文将主要就DEAA的形态问题展开研究。     

Molecular organization of reactants in the kinetics and catalysis of liquid phase reactions: XII. Mechanism of the boron trifluoride-catalyzed Curtius thermal rearrangement of benzoyl azide into phenyl isocyanate

The kinetics of the thermal decomposition and rearrangement of benzoyl azide into phenyl isocyanate was studied in n-heptane in the presence of boron trifluoride etherate as the catalyst. The apparent activation energy of the noncatalytic reaction is 28.0 kcal/mol, and that of the catalytic reaction is 11.0 kcal/mol. The electronic structure and geometry of various complexes between benzoyl azide and BF₃ were studied using the PBE/TZ2P density functional method, and fragments of the potential energy surface were calculated for the catalytic rearrangement. Comparatively stable 1: 1 and 1: 2 complexes between the syn conformer of benzoyl azide and the catalyst can form in the system by coordination to the oxygen and nitrogen atoms of the acyl azide group. The heats of formation of these complexes are between ?1.7 and ?6.4 kcal/mol. The main consequence of the formation of these complexes is that the acyl azide group comes out of the benzene ring plane and thus becomes more reactive. The effective activation energies calculated for the catalytic rearrangement involving complexes of different compositions are 12–15 kcal/mol lower the effective activation energy of the noncatalytic reaction. Information has been obtained about the structure of the transition state of the catalytic reaction, in which a nitrogen molecule is abstracted from benzoyl azide with a synchronous rearrangement of other atoms, resulting in the formation of the ultimate product.     

Observation of photochemical C-N bond cleavage in CH3N3: a new photochemical route to cyclic N3

We report VUV-photoionization based photofragmentation-translational spectroscopy data, providing a comprehensive study of the collision free photochemistry of methyl azide (CH3N3) at 193 nm. We report the first observation of the production of methyl and the N3 radical and derive the translational energy release distribution of this reaction. The most probable translation energy is only 8%, and the maximum translational energy is only 60% of the available energy, taking CH3 + linear N3 as the zero of energy. However, the maximum translational energy release is quantitatively consistent with production of the higher energy isomer cyclic N3. Threshold photoionization of the N3 fragment using tunable synchrotron radiation shows results consistent with theoretical predictions of the cyclic N3 ionization potential. The secondary dissociation of N3 --> N(2D) + N2 is also observed and its translational energy release is derived. This distribution peaks at approximately 6 and extends to 11 kcal/mol as would be expected from the size of the exit channel barrier for spin-allowed dissociation of cyclic N3 (7 kcal/mol) and, furthermore, inconsistent with the barrier height of the spin-allowed dissociation of linear N3 (3 kcal/mol). A large fraction (approximately 45%) of the N3 does not dissociate on the microsecond time scale of the experiment suggesting methyl azide may be the most attractive photochemical precursor of cyclic N3 yet found.     

Synthesis of azido-polymers of butadiene

Iodine azide adds to cyclohexene in acetonitrile or 4:1 methylene chloride/acetonitrile to give trans-1-azido-2-iodocyclohexane. In methylene chloride this reaction gives a mixture of the cis-and trans-iodoazides owing to competing radical addition. Iodine azide adds to 1-hexene in acetonitrile by an ionic mechanism to give a 3:1 mixture of the 2-azido-1-azido- and 1-azido-2-iodohexanes. Dehydroiodination of the model iodoazides proceeds smoothly with potassium t-butoxide in diethyl ether or THF in the presence of 5 mol % 18-crown-6 at room temperature, giving in the previous example a mixture of 2-azido- and trans-1-azidohexenes. Polybutadiene, carboxyterminated poly(acrylonitrile-co-butadiene), and hydroxy-terminated polybutadiene gave iodoazide derivatives with up to 96% of the theoretical maximum nitrogen content and strong azide IR absorption. High azidoiodination gave polymer with N₃/I ratios slightly higher than unity while low percent azidoiodination led to polymer with N₃/I ratios of as low as 2:3. All of the nitrogen introduced was in the form of azide function. Dehydroiodination gave polymers with vinyl azide functionality and caused loss of some of the azide groups. All the azidoiodinated polymers decomposed between 120 and 160°C. The dehydroiodinated materials were less stable, decomposing between 100 and 150°C. The temperature of initial decomposition decreased as azide content increased. Polymers with >55–60% of the theoretical maximum azide content were shock sensitive.     

Competition between alpha-cleavage and energy transfer in alpha-azidoacetophenones

Molecular modeling demonstrates that the first excited state of the triplet ketone (T1K) in azide 1b has a (pi,pi*) configuration with an energy that is 66 kcal/mol above its ground state and its second excited state (T2K) is 10 kcal/mol higher in energy and has a (n,pi*) configuration. In comparison, T1K and T2K of azide 1a are almost degenerate at 74 and 77 kcal/mol above the ground state with a (n,pi*) and (pi,pi*) configuration, respectively. Laser flash photolysis (308 nm) of azide 1b in methanol yields a transient absorption (lambdamax=450 nm) due to formation of T1K, which decays with a rate of 2.1 x 105 s-1 to form triplet alkylnitrene 2b (lambdamax=320 nm). The lifetime of nitrene 2b was measured to be 16 ms. In contrast, laser flash photolysis (308 nm) of azide 1a produced transient absorption spectra due to formation of nitrene 2a (lambdamax=320 nm) and benzoyl radical 3a (lambdamax=370 nm). The decay of 3a is 2 x 105 s-1 in methanol, whereas nitrene 2a decays with a rate of approximately 91 s-1. Thus, T1K (pi,pi*) in azide 1b leads to energy transfer to form nitrene 2b; however, alpha-cleavage is not observed since the energy of T2K (n,pi*) is 10 kcal/mol higher in energy than T1K, and therefore, T2K is not populated. In azide 1a both alpha-cleavage and energy transfer are observed from T1K (n,pi*) and T2K (pi,pi*), respectively, since these triplet states are almost degenerate. Photolysis of azide 1a yields mainly product 4, which must arise from recombination of benzoyl radicals 3a with nitrenes 2a. However, products studies for azide 1b also yield 4b as the major product, even though laser flash photolysis of azide 1b does not indicate formation of benzoyl radical 3b. Thus, we hypothesize that benzoyl radicals 3 can also be formed from nitrenes 2. More specifically, nitrene 2 does undergo alpha-photocleavage to form benzoyl radicals and iminyl radicals. The secondary photolysis of nitrenes 2 is further supported with molecular modeling and product studies.     

Observation of inductive effects that cause a change in the rate-determining step for the conversion of rhenium azides to imido complexes

The cationic oxorhenium(V) complex [Re(O)(hoz)(2)(CH(3)CN)][B(C(6)F(5))(4)] [1; Hhoz = 2-(2'-hydroxyphenyl)-2-oxazoline] reacts with aryl azides (N(3)Ar) to give cationic cis-rhenium(VII) oxoimido complexes of the general formula [Re(O)(NAr)(hoz)(2)][B(C(6)F(5))(4)] [2a-2f; Ar = 4-methoxyphenyl, 4-methylphenyl, phenyl, 3-methoxyphenyl, 4-chlorophenyl, and 4-(trifluoromethyl)phenyl]. The kinetics of formation of 2 in CH(3)CN are first-order in both azide (N(3)Ar) and oxorhenium(V) complex 1, with second-order rate constants ranging from 3.5 × 10(-2) to 1.7 × 10(-1) M(-1) s(-1). A strong inductive effect is observed for electron-withdrawing substituents, leading to a negative Hammett reaction constant ρ = -1.3. However, electron-donating substituents on phenyl azide deviate significantly from this trend. Enthalpic barriers (ΔH(?)) determined by the Eyring-Polanyi equation are in the range 14-19 kcal mol(-1) for all aryl azides studied. However, electron-donating 4-methoxyphenyl azide exhibits a large negative entropy of activation, ΔS(?) = -21 cal mol(-1) K(-1), which is in sharp contrast to the near zero ΔS(?) observed for phenyl azide and 4-(trifluoromethyl)phenyl azide. The Hammett linear free-energy relationship and the activation parameters support a change in the mechanism between electron-withdrawing and electron-donating aryl azides. Density functional theory predicts that the aryl azides coordinate via N(α) and extrude N(2) directly. For the electron-withdrawing substituents, N(2) extrusion is rate-determining, while for the electron-donating substituents, the rate-determining step becomes the initial attack of the azide. The barriers for these two steps are inverted in their order with respect to the Hammett σ values; thus, the Hammett plot appears with a break in its slope.     

Dynamic ligand exchange of the lanthanide complex leading to structural and functional transformation: one-pot sequential catalytic asymmetric epoxidation-regioselective epoxide-opening process

The characteristic property of the lanthanide complex, which easily undergoes a dynamic ligand exchange and alters its structure and function in situ, is described. After the completion of the catalytic asymmetric epoxidation of various alpha,beta-unsaturated amides 2 in the presence of the Sm-(S)-BINOL-Ph3As=O (1:1:1) complex 1 (2-10 mol %), the addition of Me3SiN3 directly to the reaction mixture led to smooth epoxide-opening at room temperature, affording the corresponding anti-beta-azido-alpha-hydroxyamide 4 in excellent overall yield (up to 99%) with complete regioselectivity and excellent enantiomeric excess (up to >99%). The key to the success of the sequential process was the in situ generation of the highly reactive samarium azide complex through dynamic ligand exchange. In situ IR spectroscopy and other experiments provided strong evidence that the samarium azide complex was generated. In addition, the relatively high Lewis basicity of the amide moiety had a key role in the high reactivity of both the epoxidation and the epoxide-opening reactions. Examinations of other nucleophiles such as sulfur or carbon nucleophiles as well as transformations of epoxide-opened products are also described.     

Synthesis of chiral organocatalysts derived from aziridines: application in asymmetric aldol reaction

We report the synthesis of a new series of highly efficient chiral organocatalysts derived via the regio- and stereoselective ring opening of chiral aziridines with azide anions. The catalysts have proved to be very efficient for a direct asymmetric aldol reaction, both with cyclic as well as acyclic ketones in brine with 2 mol % of catalyst loading, and afforded the products in excellent yields (up to 99%) and enantioselectivities (up to >99%). The chiral aldol adduct obtained has further been converted to a chiral azetidine ring via a convenient pathway.     

Microwave-Assisted,Multicomponent, Ecofriendly Synthesis of 3-Bihetaryl-2-oxindole Derivatives Grafted with Phenothiazine Moiety

A series of 3-(3′-pyrrolyl)-2-oxindoles incorporating the phenothiazine moiety has been synthesized under both conventional and microwave heating conditions via multicomponent reaction of 3-(2-(phenothiazin-2-yl)-2-oxoethylidene)-2-oxindole derivatives, acyclic and cyclic 1,3-dicarbonyl compounds, and ammonium acetate. The resulting 2-oxindole derivatives underwent selective chloroacetylation at both the oxindole and the phenothiazine NH groups. Treatment of the dichloroacetylated compound with 2 mol of sodium azide in acetone under reflux gave the corresponding monoazide with concomitant dechloroacetylation of the N-chloroacetyl group of the oxindole ring. Huisgen 1,3-dipolar cycloaddition of the resulted alkyl azide with diethyl acetylene–dicarboxylate afforded the corresponding triazole derivative in good yield. Furthermore, the dichloroacetylated compound could be easily cyclized into 4-(3-oxo-2,3-dihydroxazolo[3,2-a]indol-9-yl)-1H-pyrrole-3-carboxylate derivative by treatment with sodium hydride in dry toluene. The yields and rate of reactions significantly improved under microwave heating conditions.     

Azide/alkyne‐“click”‐reactions on amino resin materials: An LC‐ESI‐TOF analysis

This article describes the reaction of amino resins with functional molecules using the azide/alkyne‐“click”‐reaction, opening a simple chemical modification of amino resins under aqueous conditions. Alkyne‐modified melamine‐formaldehyde resins are prepared via a direct cocondensation approach using propargylic alcohol (21.6–86.3 mmol) as additive. Subsequently, alkyne‐modified mono‐, bi‐, and trinuclear melamine‐species are identified via LC‐ESI‐TOF methods proving the covalent incorporation of alkyne‐moieties in amounts of up to 3.9 mol %. Subsequent modification of the alkyne‐modified resins was accomplished by reaction of functional azides (octyl azide (1), (azidomethyl)benzene (2), 1‐(6‐azidohexyl) thymine (3), and 4‐azido‐N‐(2,2,6,6‐tetramethylpiperidin‐4‐yl)benzamide (4)) with Cu(I)Br and DIPEA as a base. The formation of triazolyl‐modified MF‐resins was proven by LC‐ESI‐TOF methods, indicating the successful covalent modification of the amino resin with the azides 1 – 4 . © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Direct measurements of the rate constants of the reactions NCN + NO and NCN + NO2 behind shock waves

The high-temperature rate constants of the reactions NCN + NO and NCN + NO(2) have been directly measured behind shock waves under pseudo-first-order conditions. NCN has been generated by the pyrolysis of cyanogen azide (NCN(3)) and quantitatively detected by sensitive difference amplification laser absorption spectroscopy at a wavelength of 329.1302 nm. The NCN(3) decomposition initially yields electronically excited (1)NCN radicals, which are subsequently transformed to the triplet ground state by collision-induced intersystem crossing (CIISC). CIISC efficiencies were found to increase in the order of Ar < NO(2) < NO as the collision gases. The rate constants of the NCN + NO/NO(2) reactions can be expressed as k(NCN+NO)/(cm(3) mol(-1)s(-1)) = 1.9 × 10(12) exp[-26.3 (kJ/mol)/RT] (±7%,ΔE(a) = ± 1.6 kJ/mol, 764 K < T < 1944 K) and k(NCN+NO(2))/(cm(3) mol(-1)s(-1)) = 4.7 × 10(12) exp[-38.0(kJ/mol)/RT] (±19%,ΔE(a) = ± 3.8 kJ/mol, 704 K < T < 1659 K). In striking contrast to reported low-temperature measurements, which are dominated by recombination processes, both reaction rates show a positive temperature dependence and are independent of the total density (1.7 × 10(-6) mol/cm(3) < ρ < 7.6 × 10(-6) mol/cm(3)). For both reactions, the minima of the total rate constants occur at temperatures below 700 K, showing that, at combustion-relevant temperatures, the overall reactions are dominated by direct or indirect abstraction pathways according to NCN + NO → CN + N(2)O and NCN + NO(2) → NCNO + NO.     

Detoxifying Polyhalogenated Catechols through a Copper‐Chelating Agent by Forming Stable and Redox‐Inactive Hydrogen‐Bonded Complexes with an Unusual Perpendicular Structure

The use of selective metal chelating agents with preference for binding of a specific metal ion to investigate its biological role is becoming increasingly common. We found recently that a well‐known copper‐specific chelator 2,9‐dimethyl‐1,10‐phenanthroline (2,9‐Me₂OP) could completely inhibit the synergistic toxicity induced by tetrachlorocatechol (TCC) and sodium azide (NaN₃). However, its underlying molecular mechanism is still not clear. Here, we show that the protection by 2,9‐Me₂OP is not due to its classic copper‐chelating property, but rather due to formation of a multiple hydrogen‐bonded complex between 2,9‐Me₂OP and TCC, featuring an unusual perpendicular arrangement of the two binding partners. The two methyl groups at the 2,9 positions in 2,9‐Me₂OP were found to be critical to stabilize the 2,9‐Me₂OP/TCC complex due to steric hindrance, and therefore completely prevents the generation of the reactive and toxic semiquinone radicals by TCC/NaN₃. This represents the first report showing that an unexpected new protective mode of action for the copper “specific” chelating agent 2,9‐Me₂OP by using its steric hindrance effect of the two CH₃ groups not only to chelate copper, but also to “chelate” a catechol through multiple H‐bonding. These findings may have broad biological implications for future research of this widely used copper‐chelating agent and the ubiquitous catecholic compounds.     

The stabilization of managese(III) by azide ions in aqueous solution

The evidences of spontaneous oxidation of Mn(II) by the dissolved oxygen in azide buffer medium, which is dependent on the N (-)(3)HN (3) concentration, suggested a formation of stable Mn(III) complexes due to marked colour changes. Spectrophotometric studies combined with coulometric generation of Mn(III), in presence of large excess of Mn(II), showed a maximum absorbance peak at 432 nm. The molar absorptivity increases with azide concentration (0.44-3.9 mol 1(-1)) from 3100 to 6300 mol(-1) 1 cm(-1), showing a stepwise complex formation. Potential measurements of the Mn(III) Mn(II) system in several azide aqueous buffers solutions: 1.0 x 10(-2) mol 1(-1) HN(3), (0.50-2.0 mol 1(-1)) N(-)(3) and 5.0 x 10(-2) mol 1(-1) Mn(II) and constant ionic strength 2.0 mol 1(-1), kept with sodium perchlorate, leads to the conditional potential, E(0')x, in several azide concentrations at 25.0 +/- 0.1 degrees C. Considering the overall formation constants of Mn(II) N (-)(3), from former studies, and the potential, E(0')s = 1.063 V versus SCE, for Mn(III) Mn(II) system in non-complexing media, it was possible to calculate the Fronaeus function, F(0)(L), and the following overall formation constants: beta(1) = 1.2 x 10(5) M(-1), beta(2) = 6.0 x 10(8) M(-2), beta(3) = (2.4 +/- 0.7) x 10(11) M(-3), beta(4) = (1.5 +/- 0.5) x 10(11) M(-4) and beta(5) = (9.6 +/- 0.8) x 10(11) M(-5) for the Mn(III) N (-)(3) complexes. These data give important support to understand the importance of Mn(II) and Mn(III) synergistic effect on the analytical method of S(IV) determination based on the Co(II) autoxidation.     

A comparison of acetyl- and methoxycarbonylnitrenes by computational methods and a laser flash photolysis study of benzoylnitrene

Density functional theory (DFT), CCSD(T), and CBS-QB3 calculations were performed to understand the chemical and reactivity differences between acetylnitrene (CH(3)C(=O)N) and methoxycarbonylnitrene (CH(3)OC(=O)N) and related compounds. CBS-QB3 theory alone correctly predicts that acetylnitrene has a singlet ground state. We agree with previous studies that there is a substantial N-O interaction in singlet acetylnitrene and find a corresponding but weaker interaction in methoxycarbonylnitrene. Methoxycarbonylnitrene has a triplet ground state because the oxygen atom stabilizes the triplet state of the carbonyl nitrene more than the corresponding singlet state. The oxygen atom also stabilizes the transition state of the Curtius rearrangement and accelerates the isomerization of methoxycarbonylnitrene relative to acetylnitrene. Acetyl azide is calculated to decompose by concerted migration of the methyl group along with nitrogen extrusion; the free energy of activation for this concerted process is only 27 kcal/mol, and a free nitrene is not produced upon pyrolysis of acetyl azide. Methoxycarbonyl azide, on the other hand, does have a preference for stepwise Curtius rearrangement via the free nitrene. The bimolecular reactions of acetylnitrene and methoxycarbonylnitrene with propane, ethylene, and methanol were calculated and found to have enthalpic barriers that are near zero and free energy barriers that are controlled by entropy. These predictions were tested by laser flash photolysis studies of benzoyl azide. The absolute bimolecular reaction rate constants of benzoylnitrene were measured with the following substrates: acetonitrile (k = 3.4 x 10(5) M(-1) (s-1)), methanol (6.5 x 10(6) M(-1) s(-1)), water (4.0 x 10(6) M(-1) s(-1)), cyclohexane (1.8 x 10(5) M(-1) s(-1)), and several representative alkenes. The activation energy for the reaction of benzoylnitrene with 1-hexene is -0.06 +/- 0.001 kcal/mol. The activation energy for the decay of benzoylnitrene in pentane is -3.20 +/- 0.02 kcal/mol. The latter results indicate that the rates of reactions of benzoylnitrene are controlled by entropic factors in a manner reminiscent of singlet carbene processes.     

Studies on multistep thermal decomposition behavior of polytriazole polyethylene oxide‐tetrahydrofuran elastomer

Polytriazole polyethylene oxide‐tetrahydrofuran (PTPET) is an energetic propellant elastomer that is prepared using glycidyl azide polymer and trifunctional alkynyl‐terminated polyethylene oxide‐tetrahydrofuran. Its thermal decomposition, determined using thermogravimetic analysis, showed two mass‐loss peaks largely related to the decomposition of azide groups and the main chain. Flynn‐Wall‐Ozawa and Kissinger‐Akahira‐Sunose methods were deployed to obtain kinetic triplet parameters of PTPET thermal decomposition by the traditional model‐free method; the Coats‐Redfern approach was used as the model‐fitting method. Kinetics analysis indicated that the mechanism of the two‐step reactions were the primary‐reaction of first order and the power‐law phase reaction of the 2/3 order. The first decomposition stage of PTPET had an activation energy (E_a) of 113 to 116 kJ/mol while the second was 196 to 210 kJ/mol. The thermal decomposition of PTPET with different heating rates and mechanisms showed good kinetic compensation effects, the gas products being further studied with TG‐FTIR.     

Nitrogen-ligated iron complexes: photolytic approach to the FeN+ moiety

The synthesis of (PNP)FeCl, (PNP)Fe[NH(xylyl)], and (PNP)FeN3 are reported(PNP = (tBu2PCH2SiMe2)2N-). While the azide is thermally stable, it is photosensitive to lose N2 and form [(PNPN)Fe]2,in which the nitride ligand has formed a double bond to one phosphorus, and this N bridges to a second iron to form a 2-fold symmetric dimer. The reaction energy to form the (undetected) monomeric [eta3- tBu2PCH2SiMe2NSiMe2CH2PtBu2N]Fe is -15.9 kcal/mol, so this PIII --> PV oxidation is favorable. The eta2 version of this same species is less stable by 23.7 kcal/mol, which shows that the loss of one P--> Fe bond is caused by dimerization, and therefore, it does not precede and cause dimerization. A comparison is made to Ru analogs.