Comparison of free and metal coordinated 1,4-disubstituted-1,4-diaza-1,3-butadienes : Crystal and molecular structures of 1,4-dicyclohexyl-1,4-diaza-1,3-butadiene and trans-[dichloro(triphenylphosphine)(1,4-di-tert-butyl- 1,4-diaza-1,3-butadiene)palladium(II)]

The crystal and molecular structures of c-Hex-DAB (c-hexyl-NC(H)C(H)N-c-hexyl; DAB = 1,4-diaza-1,3-butadiene) and of trans-[PdCl₂(PPh₃)(t-Bu-DAB)] are reported. Crystals of c-Hex-DAB are monoclinic with space group C_2/c and cell constants: a = 24.70(1), b = 4.660(2), c = 12.268(3)Å, β = 107.66(4)°, Z = 4. The molecule has a flat E-s-trans-E structure with bond lengths of 1.258(3)Å for the CN double bond and 1.457(3)Å for the central CC′ bond. These bond lengths and the NC-C′ angle of 120.8(2)° indicate that the C- and N-atoms are purely sp²-hybridized and that there is little or no conjugation within the central DAB skeleton. Crystals of trans-[PdCl₂(PPh₃)(t-Bu-DAB)] are triclinic with space group P-1 and cell constants: a = 17.122(3), b = 18.279(3), c = 10.008(5)Å, α = 96.77(2), β = 95.29(3), γ = 109.79(2). Z = 4. The t-Bu-DAB ligand is coordinated to the metal via one lone pair only. In this 2e; σ-N coordination mode the E-s-trans-E conformation of the free DAB-ligand is still present and the bonding distances within the DAB-ligand are hardly affected. [CN: 1.261(10)Å; CC′: 1.479(10)Å (mean).] The PdN-, NC- and central CC′-bond lengths are compared with those found in other metal -R-DAB complexes.     

Syntheses and structures of the cobalt, nickel, and zinc complexes with 1,4-diaza-1,3-butadiene ligands

Several cobalt(II), nickel(II), and zinc(II) complexes with a series of ligands of the 1,4-diaza-1,3-butadiene type bearing aryl (2,6-di-iso-propylphenyl, mesityl) and alkyl (tert-butyl, iso-propyl) substituents at the nitrogen atoms are synthesized. The obtained complexes are characterized by X-ray structure analysis, IR spectroscopy, and elemental analysis.     

Comparison of catalytic properties of systems based on nickel complexes with 1,4-diaza-1,3-butadiene ligands in reactions of styrene hydrogenation and ethylene polymerization

Turnover frequencies of catalytic systems based on nickel complexes with 1,4-diaza-1,3-butadiene (α-diimine) ligands in the reactions of styrene hydrogenation and ethylene polymerization were determined. Results are presented of a study by the electron paramagnetic resonance method and IR spectroscopy of 1,4-diaza-1,3-butadiene complexes of nickel(II) and anion radicals formed in the interaction of the starting components under the conditions of catalysis. It was shown that the paramagnetic Ni(I) complexes are precursors of complexes catalytically active in the hydrogenation and polymerization reactions.     

1,4-regioselective iodofunctionalizations of 1,3-butadiene

Addition reactions of benzene and acetonitrile to 1,3-butadiene are described. This new iodofunctionalization process proceeds “via” iodonium ion-allylic cation equilibrium and gives regioselectively 1,4-adducts, which can be alternatively obtained by acid treatment of the 1,2-derivative 8.     

Mixed alkyl isocyanide-1,4-diaza-1,3-butadiene complexes of molybdenum(II) and tungsten(II)

The reactions of M(CO)₄(R′-DAB) (M = Mo) or W; R′-DAB = R′-N=CHCH=NR′ (R′ = i-propyl, t-butyl, or cyclohexyl) with SnCl₄ in dichloromethane solution result in the formation, in high yield, of the orange, diamagnetic, seven-coordinate oxidative-addition products M(CO)₃(R′-DAB)(SnCl₃)Cl. The reactions of Mo(CO)₃(R′-DAB)(SnCl₃)Cl (R′ = i-Pr or Cy) with an excess of alkyl isocyanide RNC (R = CHMe₂, CMe₃, or C₆H₁₁) in the presence of KPF₆ lead to the formation of [Mo(CNR)₄(R′-DAB)Cl]PF₆ or [Mo(CNR)₅(R′-DAB)](PF₆)₂ depending upon the reaction stoichiometry and reaction conditions. The monocationic chloro species are converted to [Mo(CNR)₅(R′-DAB)](PF₆)₂ upon reflux with the stoichiometric amount of RNC. Under similar reactions conditions M(CO)₃(t-Bu-DAB)(SnCl₃)Cl (M = Mo or W) derivatives react with alkyl isocyanides with the reductive-elimination of the elements of SnCl₄ and the formation of octahedral M(CO)₃(CNR)(t-Bu-DAB). The dark red compounds [Mo(CNCMe₃)₅(R′-DAB)](PF₆)₂ (R′ = i-Pr or Cy) react readily with cyanide ions at ambient temperatures in methanol to yield [Mo(CNCMe₃)₄(R′-DAB)(CN)]PF₆. Attempts to thermally dealkylate the parent complexes [Mo(CNCMe₃)₅(R′-DAB)](PF₆)₂ (R′ = i-Pr or Cy) to these same cyano species were unsuccessful.     

Photochemical and discharge-driven pathways to aromatic products from 1,3-butadiene

A detailed study of the photochemical and discharge-driven pathways taken by gas-phase 1,3-butadiene has been carried out. Photolysis or discharge excitation was initiated inside a short reaction tube attached to the outlet of a pulsed valve. Bath gas temperatures near 100 K were achieved in the reaction tube by the constrained expansion of the gas mixture into the tube, simulating temperatures of relevance in Titan's atmosphere. Photolysis of 1,3-butadiene was initiated at 218 nm with a laser pulse that counter-propagated the reaction tube. Discharge excitation was carried out using discharge electrodes imbedded in the reaction tube walls, enabling the study of the photochemical and discharge products under similar conditions. Products were detected using either single-photon VUV photoionization (118 nm = 10.5 eV) or resonant two-photon ionization (R(2)PI) spectroscopy in a time-of-flight mass spectrometer. Emphasis was placed on characterization of the aromatic products formed, since these may be of particular relevance to Titan's atmosphere, where benzene has been positively identified and 1,3-butadiene is projected as the principle pathway to its formation. Consistent with previous studies of the photodissociation of 1,3-butadiene, C(3)H(3) + CH(3) is the dominant primary product formed. Under the temperature-pressure conditions present in the reaction tube (T approximately 75-100 K, P = 50 mbar), C(6)H(6) is the dominant secondary photochemical product formed. A 1:1 C(4)H(6):C(4)D(6) mixture was used to prove that the C(6)H(6) product was formed by recombination of two C(3)H(3) radicals; however, a careful search for benzene revealed none, indicating that less than 1% of the C(6)H(6) formed in the reaction tube is benzene. This is consistent with expectations for these temperatures and pressures based on previous modeling of propargyl recombination. Two aromatic products were observed from the photochemistry: ethylbenzene and 3-phenylpropyne. Plausible pathways leading to these products are proposed. In the discharge, C(3)H(3) + CH(3) are also identified as significant primary neutral products and C(6)H(6) as a dominant higher-mass product. In this case, the C(6)H(6) was identified as benzene via its R2PI spectrum, appearing with intensity about 10 times larger than any other aromatic formed in the discharge. R2PI spectra of a total of about 15 aromatic products were recorded from the 1,3-butadiene discharge, among them toluene; styrene; phenylacetylene; o-, m-, and p-xylene; ethylbenzene; indane; indene; beta-methylstyrene; and naphthalene. Previously unidentified spectra in the m/z 142 and 144 mass channels were positively identified as the 1,3- and 1,4-isomers of phenylcyclopentadiene and the analogous 1-phenylcyclopentene.     

Efficient synthesis and environmentally friendly reactions of PEG-supported 1,2-diaza-1,3-butadiene

[reaction: see text] Here, we report the protocol for the preparation of new poly(ethylene glycol)-supported 1,2-diaza-1,3-butadiene. In addition, we discuss an application of this supported reagent in an efficient and environmentally friendly one-pot synthesis of 2-thiazol-4-one derivatives by reaction with thioamides.     

Preparation,copolymerization kinetics,and viscoelastic behavior of copolymers of 1,3-butadiene and 1,4-diphenyl-1,3-butadiene

1,4-Diphenyl-1,3-butadiene reacts readily with sec-butyllithium in toluene to form adducts. Although this 1,4-substituted conjugated diene did not homopolymerize or copolymerize with styrene, with butadiene it formed copolymers having compositions varying from one end of the chain to the other. The monomer reactivity ratios found were r₁ = 8.2, r₂ = 0 in toluene and r₁ = 2.1, r₂ = 0 in toluene–tetrahydrofuran (0.2%) solution. The intramolecular composition distribution of these polymers varied from an initial butadiene-rich composition, dependent on the ratio of monomers charged, to the equimolar composition of the alternating copolymer. In spite of this compositional heterogeneity, the crosslinked polymers exhibited a single glass transition characteristic of the mean composition. A secondary, high-temperature dispersion observed in the dynamic viscoelastic properties of some of the products is shown to be attributable to network topological effects.     

Cycloaddition of a 1,2-diaza-1,3-butadiene to phenylpropiolic acid: an efficient route to pyridazinoquinolone derivatives

Diazocoupling of dihydroquinolin-4-ones with aryldiazonium nitrates gave the corresponding diazo derivatives, which undergo facile (4+2) cycloaddition reactions with phenylpropiolic acid to afford 2-aryl-4a-methyl-10-oxo-4-phenyl-2,4a,5,10-tetrahydropyridazino[4,3-b]quinoline-3-carboxylic acid derivatives 3. However, with β-nitrostyrene a mixture of three isomeric products 4a-c was obtained.     

Free radicals derived from 1,4-diaza-1,3-butadiene: II. Adducts with metal carbonyls and reactions with derivatives of group VB elements

The paramagnetic adducts formed when photochemically generated Mn(CO)₅ or Re(CO)₅ radicals are trapped by N,Nt?-di-t-butyl-1,4-diaza-1,3-butadiene (t-Bu-DAB) have been characterized by ESR spectroscopy. Adducts containing phosphorus have also been observed but attempts to produce adducts containing As, Sb or Bi have been unsuccessful. In a number of systems an identical ESR spectrum was observed. This has been shown to arise from the N,N′-di-t-butylpyrazinium cation.     

氰基蒽敏化1,4-二苯基-1,3-丁二烯光氧化反应的研究

本文报道1,4-二苯基1,3-丁二烯的氰基蒽敏化光氧化反应,讨论了反应机理,在溶剂乙腈和四氯化碳中,荧光淬灭、激基复合物及其自由能变化支持了电子转移反应机制,在四氯化碳中的反应与在极性溶剂乙腈中的完全不同,在四氯化碳中进行的完全是单线态氧的反应,而在乙腈中则发生负氧离子的氧化反应。从乙腈中的反应,我们分离得用臭氧直接氧化时难以得到的臭氧化物-3-苯基5(2-苯基)-乙烯基-1,2,4-三氧杂环戊烷。     

1,4-二苯基-1,3-丁二烯的氰基蒽敏化光氧化反应

某些不能与单线态氧(~1O_2)起反应的烯烃、炔烃、硫醚和环氧化合物,在以氰基蒽为敏化剂的条件下,可发生经由光敏电子转移机理的氧化反应.近年来,Santamaria 等,Foote 等和我们都在研究这类反应.本文报道以9,10-二氰基蒽(DCA)为敏化剂、反,反-1,4-二苯基-1,3-丁二烯为反应物的电子转移光敏氧化反应,并讨论了反应机理.     

Addition of amine derivatives to phosphorylated 1,2-diaza-1,3-butadienes. Synthesis of α-aminophosphonates

Achiral and chiral 1,2-diaza-1,3-butadienes derived from phosphine oxides and phosphonates are obtained from hydrazonoalkyl-phosphine oxides and -phosphonates. Michael addition (1,4-addition) of ammonia, aminoesters and aminoalcohols to these azo-alkenes gives functionalized α-amino-phosphine oxides and -phosphonates.