7299-37-8Relevant articles and documents
Generation and Identification of Four Stable Isomeric + Ions by Direct Dissociative Ionization or by Charge Reversal of Anions
Burgers, Peter C.,Holmes, John L.,Mommers, Alexander A.,Szulejko, Jan E.
, p. 521 - 524 (1984)
Examination of collisional activation mass spectra showed that pure + was generated by only metastably fragmenting precursor ions, +., +., and +..Pure +> could be produced from the dissociative ionization of in the ion source and among metastably fragmenting ions.The ions +> and +> were generated by collisionally induced charge inversion of the corresponding anions.The latter were produced by dissociative electron capture and by reaction of OH- with cyclopropene and CH3CCD, respectively.Although +> exists in a potential well, +> ions produced by the above method lie close to their dissociation limit. +> and +> ions generated by charge reversal rearrange to similar mixtures of + and +> within a time of ca. 8 μs.The fragmentations + -> + + H2 and + -> + + C2H2 produce composite metastable peaks.The high and low kinetic energy release components therein were shown to result from the generation of + and +>, respectively.
Photoelectron Spectroscopy of the Allenyl Ion CH2=C=CH-
Oakes, John M.,Ellison, G. Barney
, p. 2969 - 2975 (1983)
We have studied the photodetachment spectra of CH2=C=CH-, CD2=C=CH-, and CH2=C=CD-.By comparing the photoelectron spectra of these selectivity labeled species, we conclude that the ion has an allenyl (rather than propargyl) structure.The electron affinities (EA) of a set of propargyl radicals are as follows: EA(CH2C=*CH)= 0.893 +/- 0.025 eV, EA(CD2C=*CH) = 0.907 +/- 0.023 eV, and EA(CH2C=*CD) = 0.88 +/- 0.15 eV.A single active vibration is observed in the photoelectron spectra of CH2=C=CH- and CD2=C=CH-.This mode has a frequency of 510 cm-1 and is assigned as an out-of-plane bend of the acetylenic hydrogen of the propargyl radical (either CH2C=*CH or CD2C=*CH).The gas-phase acidity of allene and methylacetylene are reported as ΔH0acid(H-CH2CCH) = 382.3 +/- 1.2 kcal/mol and ΔH0acid(H-CH=C=CH2) = 380.7 +/- 1.2 kcal/mol.The ΔHf0298(CH2=C=CH-) is 59.4 +/- 1.2 kcal/mol.
Diverse catalytic activity of the cationic actinide complex [(Et2N)3U][BPh4] in the dimerization and hydrosilylation of terminal alkynes. Characterization of the first f-element alkyne π-complex [(Et2N)2U(CCtBu)(η2-HCC tBu)][BPh4]
Dash, Aswini K.,Wang, Jia Xi,Berthet, Jean Claude,Ephritikhine, Michel,Eisen, Moris S.
, p. 83 - 98 (2007/10/03)
The cationic actinide complex [(Et2N)3U][BPh4] is an active catalytic precursor for the selective dimerization of terminal alkynes. The regioselectivity is mainly towards the geminal dimer but for bulky alkyne substituents, the unexpected cis-dimer is also obtained. Mechanistic studies show that the first step in the catalytic cycle is the formation of the acetylide complex [(Et2N)2UCCR][BPh4] with the concomitant reversible elimination of Et2NH, followed by the formation of the alkyne π-complex [(Et2N)2UCCR(RCCH)][BPh4]. This latter complex (R=tBu) has been characterized spectroscopically. The kinetic rate law is first order in organoactinide and exhibits a two domain behavior as a function of alkyne concentration. At low alkyne concentrations, the reaction follows an inverse order whereas at high alkyne concentrations, a zero order is observed. The turnover-limiting step is the CC bond insertion of the terminal alkyne into the actinide-acetylide bond to give the corresponding alkenyl complex with ΔH?=15.6(3) kcal mol-1 and ΔS?=-11.4(6) eu. The following step, protonolysis of the uranium-carbon bond of the alkenyl intermediate by the terminal alkyne, is much faster but can be retarded by using CH3CCD, allowing the formation of trimers. The unexpected cis-isomer is presumably obtained by the isomerization of the trans-alkenyl intermediate via an envelope mechanism. A plausible mechanistic scenario is proposed for the oligomerization of terminal alkynes. The cationic complex [(Et2N)3U][BPh4] has been found to be also an efficient catalyst for the hydrosilylation of terminal alkynes. The chemoselectivity and regiospecificity of the reaction depend strongly on the nature of the alkyne, the solvent and the reaction temperature. The hydrosilylation reaction of the terminal alkynes with PhSiH3 at room temperature produced a myriad of products among which the cis- and trans-vinylsilanes, the alkene and the silylalkyne are the major components. At higher temperatures, besides the products obtained at room temperature, the double hydrosilylated alkene, in which the two silicon moieties are connected at the same carbon atom, is obtained. The catalytic hydrosilylation of (TMS)CCH and PhSiH3 with [(Et2N)3U][BPh4] was found to proceed only at higher temperatures. Mechanistically, the key intermediate seems to be the uranium-hydride complex [(Et2N)2U-H][BPh4], as evidenced by the lack of the dehydrogenative coupling of silanes. A plausible mechanistic scenario is proposed for the hydrosilylation of terminal alkynes taking into account the formation of all products.
SYNTHESIS OF E-4-CHLORO-3-PENTEN-2-ONE AND OF ITS DEUTERATED DERIVATIVES
Terpinski, Jacek,Jenike, Andrzej
, p. 613 - 615 (2007/10/02)
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