- Fluorinated butatrienes
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Major improvements in the synthesis of 1,1,4,4-tetrafluorobutatriene (1) are presented. Despite many attempts to isolate new metal complexes of 1 only an iron complex containing a ligand which is composed of a partially hydrolyzed tetrafluorobutatriene-dimer and carbon monoxide could be isolated and characterized by X-ray crystallography. Certain metal centers and solvents accelerate the decomposition of 1. First attempts to synthesize 1,1-difluorobutatriene (2) are presented which underline the major challenges of a successful synthesis of 2.
- Ehm, Christian,Akkerman, Floris A.,Lentz, Dieter
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experimental part
p. 1173 - 1181
(2011/02/16)
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- Crystal structure analysis of 1,1,4,4-tetrafluorobutadiene and experimental determination of the charge density of 1,1,4,4-tetrafluorobutatriene
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Despite its high instability, the cumulene 1,1,4,4-tetrafluorobutatriene was obtained in a crystalline form. Its X-ray structure characterization revealed the presence of a herringbone motif in the solid state (see picture). Experimental and calculated charge desity distributions show, as expected, that the central double bond is shorter and displays a higher charge density than the two outer double bonds.
- Bach, Ansgar,Lentz, Dieter,Luger, Peter,Messerschmidt, Marc,Olesch, Christian,Patzschke, Mona
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p. 296 - 299
(2007/10/03)
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- Reactions of difluorovinylidene - A super-electrophilic carbene
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Difluorovinylidene is the only vinylidene that could be isolated in low temperature matrices, so far. Its unusual reactivity is governed by its extreme electrophilicity and electron affinity. Thus, it not only adds CO and N2 without difficulties, but also inserts into CH4 and even H2 at temperatures below 40 K. The reaction of F2C=C: with FC≡CF clearly reveals that the formation of methylenecyclopropene proceeds in a stepwise reaction. The most striking example for the electrophilicity of F2C=C: is the thermal reaction with Xe to give a charge-transfer complex with a characteristic IR spectrum.
- Sander, Wolfram,Koetting, Carsten
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- Evidence for the non-concerted addition of difluorovinylidene to acetylenes
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Difluorovinylidene (1b) is an extremely electrophilic and reactive singlet carbene that can be generated in argon matrices in high yields. The thermal reaction of 1b with difluoroacetylene (2b) at 35-40K results in the formation of singlet allenylcarbene 4b as the primary product, which on subsequent irradiation with visible light (λ>420 nm) rearranges to methylenecyclopropene 3b. The new compounds were identified by IR spectroscopy in combination with density functional theory (DFT) calculations at the B3LYP/6-311G(d,p) level of theory. These results clearly demonstrate the non-concerted formation of 3b. Under similar conditions the thermal reaction of vinylidene 1b with acetylene (2c) directly leads to methylenecyclopropene 3c as the main product. Since-according to the DFT calcultations-allenylcarbene 4c is not a minimum, the formation of 3c most likely is a concerted, although highly asynchronous reaction. Visible irradiation (λ>420 nm) of 3c produces enyzme 11, which on UV irradiation gives 1,1-difluorobutatriene (10).
- Koetting, Carsten,Sander, Wolfram,Senzlober, Michael
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p. 2360 - 2365
(2007/10/03)
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