- Dual nucleophilic substitution at a W(II) η2-coordinated dIIodo acetylene leading to an amidinium carbyne complex
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The synthesis and reactivity of a W(ii) C2I2 complex towards various nucleophiles are described. Soft, aprotic nucleophiles like 4-dimethylaminopyridine (DMAP) lead to substitution of one CO at tungsten, whereas reaction with an excess of benzylamine results in a dual nucleophilic substitution at the alkyne moiety involving the rearrangement to a novel cationic amidinium carbyne complex.
- Helmdach, Kai,Rüger, Julia,Villinger, Alexander,Seidel, Wolfram W.
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Read Online
- Diiodoacetylene: Compact, strong ditopic halogen bond donor
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Diiodoacetylene, C2I2, is the smallest ditopic halogen bond donor other than I2 or other dihalogens. A convenient synthesis of diiodoacetylene from the common Sonagashira coupling reagent Me3SiC≡CH, is described. The halogen-bonded adducts of C 2I2 with dimethylformamide (DMF), pyrazine (pyz) and 1,4-diazabicyclooctane (dabco) have been characterised by X-ray crystallography. All adopt 1D halogen-bonded chains linked via short C-I...O [I...O 2.834(4)-2.888(4) A; C-I...O > 170°] or C-I...N [I...N 2.715(3)-2.832(7) A; C-I...N > 175°] interactions. Attempts to synthesise the adduct of C2I2 with hexamethylenetetramine (hmta) resulted in isolation and crystallographic characterisation of the adduct of C2I4·hmta, indicating decomposition of C2I2 to yield C 2I4 in solution. The adduct comprises two independent C2I4 molecules that act, respectively, as tetratopic and ditopic halogen bond donors forming C-I...N interactions [I...N 2.948(7)-2.999(8) A; C-I...N > 165°], occupying three of the four nitrogen sites on htma. The remaining nitrogen sites engage in N...C(π) interactions directed orthogonal to the plane of the ditopic C2I4 molecules. Separate surveys of halogen bonds formed by diiodo(poly)alkynes I(C≡C)nI (n = 1-3) and by C 2I4 molecules indicate that C-I...N halogen bonds are shorter, when normalised for van der Waals radii, and, by inference, stronger than halogen bonds involving other acceptor groups, and demonstrates that C sp-I...N halogen bonds are generally shorter Csp 2-I...N halogen bonds. The Royal Society of Chemistry 2012.
- Perkins, Catherine,Libri, Stefano,Adams, Harry,Brammer, Lee
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experimental part
p. 3033 - 3038
(2012/07/28)
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- Synthesis and properties of novel perylenebisimide-cored dendrimers
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A group of perylenebisimide-cored dendrimers with polyphenylene dendrons at four bay positions were synthesized and characterized. The electron-deficient pentafluorophenyl or cyano groups were grafted at the dendrimer surface with the aim to further increase the n-type features of the resulted dendrimers. The electrochemical and optical properties were investigated. All the dendrimers show good solubility and film-forming properties, high EA values of 3.8-3.9 eV, and high fluorescent quantum yields. All these merits indicate that they are potential multifunctional materials for application in optoelectronic devices such as solar cells or organic light-emitting devices.
- Ren, Huicai,Li, Jiuyan,Zhang, Ting,Wang, Renjie,Gao, Zhanxian,Liu, Di
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scheme or table
p. 298 - 303
(2012/07/14)
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- Synthesis and characterization of novel perylenediimide-cored dendrimer with fluorinated shell
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A perylenediimide-based dendrimer, PDI-F, was designed and synthesized for application as red host emitter in nondoped organic light-emitting diodes. PDI-F was designed with perylenediimide as the luminescence core and pentafluorophenyl rings as the surface groups. The dendrimer molecule constructed in this way is bulky and nonplanar. PDI-F exhibits good solubility in common organic solvents and is suitable for wet methods such as spin coating to make thin films. All new compounds of the intermediates and the target dendrimer were characterized by 1H NMR, 13C NMR, mass spectrometry, and elemental analysis. In addition, the ultraviolet (UV) absorption and fluorescence (FL) of PDI-F were measured and discussed. To the best of our knowledge, this is the first report of dendrimer PDI-F.
- Ren, Huicai,Li, Jiuyan,Wang, Renjie,Wang, Qian,Liu, Di
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scheme or table
p. 759 - 765
(2011/03/20)
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- Experimental Studies of the 13C NMR of Iodoalkynes in Lewis-Basic Solvents
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The 13C NMR spectra of two different iodoalkynes, 1-iodo-1-hexyne (1) and diiodoethyne (2), exhibit a strong solvent dependence. Comparisons of the data with several common empirical models, including Gutmann's Donor numbers, Reichardt's ENT, and Taft and Kamlet's β and π*, demonstrate that this solvent effect arises from a specific acid-base interaction. Solvent basicity measures such as Donor numbers and β values correlate well with the α-carbon chemical shift of 1, but polarity measures such as ENT and π* do not correlate. The similarity of the solvent effect for 1 and 2 suggests that carbon-carbon bond polarization may not play a role in the change in chemical shift, as previously hypothesized.
- Webb, Jeffrey A.,Klijn, Jaap E.,Hill, Philip Aru,Bennett, Jordan L.,Goroff, Nancy S.
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p. 660 - 664
(2007/10/03)
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- Catalyst system for the polymerization of olefins
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The present invention relates to a metal-free cyclopentadienide compound which, in conjunction with a metallocene, is able to form a catalyst system that can be used for the polymerization of olefins. It is thus possible to dispense with the use of methylaluminoxane (MAO) or boron-containing compounds as co-catalyst and nevertheless achieve a high degree of catalytic activity. The invention relates also to a process for the preparation of the metal-free cyclopentadienide compound and to the use thereof as a catalyst component in the preparation of polyolefins.
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- Halodecarboxylation of α,β-acetylenic and α,β-ethylenic acids
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Reaction of bis(collidine)iodine(I) (or bromine (I)) hexafluorophosphate with acetylenic acids led to the corresponding iodo(or bromo)acetylenes in high yields. This halodecarboxylation reaction was also observed with acrylic acids substituted in position 3 by an aryl group or an heteroatom.
- Homsi, Fadi,Rousseau, Gerard
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p. 1495 - 1498
(2007/10/03)
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- High-Resolution Infrared Study of the Fundamental Bands of Deuteroiodoacetylene
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The high-resolution infrared spectrum of deuterated iodoacetylene has been measured in the region 200-2700 cm-1. In addition to all five fundamentals, the bands 2v40 and 2v50 have been identified. The measurements were carried out by using a Fourier transform spectrometer at room temperature with instrumental resolution of about 0.0020 cm-1. The ground state rotational constants B0 = 0.0970742961 (72) cm-1, D0 = 1.38482(20) × 10-8 cm-1, and H0 = -1.47(10) × 10-15 cm-1 have been determined by combining 462 ground state combination differences from the same bands mentioned above with accurate MW data from the literature. In addition, the molecular constants for all the fundamental levels have been obtained.
- Sarkkinen,Tolonen,Alanko
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- An easy preparation of iodoacetylenes
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Reaction of terminal acetylenes with bis(sym-collidine)iodine(I) hexafluorophosphate in methylene chloride leads in good yields to the formation of iodoacetylenes.
- Brunel, Yves
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p. 2619 - 2622
(2007/10/02)
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- Small Rings, 83. - C3F2 Isomers: Generation by Pulsed Flash Pyrolysis and Matrix-Spectroscopic Identification
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Matrix-isolated difluorovinylidenecarbene (4) has been generated by pulsed flash pyrolysis from 1-chloro-3,3-difluorocyclopropene (8a) and 3,3-difluoro-1,2-diiodocyclopropene (8b).By subsequent photolysis 4 isomerizes to difluoropropargylene (5) and difluorocyclopropenylidene (6).The identification of the three new carbenes is based on the comparison of their experimental and calculated (MP2/6-31G*) infrared spectra. - Key Words: Matrix isolation / Photochemistry / Flash pyrolysis / Carbenes
- Maier, Guenther,Preiss, Thomas,Reisenauer, Hans Peter
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p. 779 - 782
(2007/10/02)
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- Reactions of α-Lithio O-Alkyloximes with Diiodomethane - a Synthesis of α-Iodomethylene Oxime Ethers
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Regiocontrolled deprotonation (e. g. lithiation) of acetone O-methyloxime (1), 5,6-dihydro-3-methyl-4H-1,2-oxazine (9a) and 4,5-dihydro-3-methylisoxazole (9b) is achieved within 1 minute at -65 deg C in hexane/THF.The lithiated compounds react very fast at low temperature (-65 deg C) with diiodomethane to give mainly the corresponding α-iodomethylene oxime ethers 6 and 11a, b.A radical mechanism of this reaction is dicussed.
- Shatzmiller, Shimon,Lidor, Ramy,Bahar, Eliezer
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p. 381 - 383
(2007/10/02)
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- 1-Iodoacetylenes. Part 2. Formation Constants of their Complexes with Lewis Bases
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Formation constants of the complexes of 1-iodoacetylenes (1)-(8) with Lewis bases (9)-(15) have been measured in solution by i.r. spectrophotometry.The stoichiometry of the complexes, the influence of the solvent on the equilibrium position, the existence of linear free energy relationships in the series of iodinated Lewis acids RI, where R=I, Br, Cl, CN, and CCX, and the relation between i.r. frequency shifts and stability constants are discussed.With any electron donor, 1-iodoacetylenes form less stable complexes than those formed by iodine cyanide.With hard bases, iodocyanoacetylene (8) and ethyliodopropiolate (7) give complexes wich are, respectively, more stable than and as stable as those with iodine; however, iodine complexes with soft bases are more stable.This is rationalized, in terms of empirical acidity scales, by the necessity to correlate the thermodynamic and spectroscopic properties of the RI complexes by a double scale equation.
- Laurence, Christian,Queignec-Cabanetos, Michele,Wojtkowiak, Bruno
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p. 1605 - 1610
(2007/10/02)
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