Kinetics and thermochemistry of the rearrangement of benzvalene to benzene. An energy sufficient but non-chemiluminescent reaction

Turro, Nicholas J.; Renner, Carl A.; Katz, Thomas J.; Wiberg, Kenneth B.; Connon, Helen A.

doi:10.1016/s0040-4039(00)74614-4

Cited by 47 publications

(32 citation statements)

References 12 publications

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“…The analogous rearrangement of benzvalene to benzene has been promoted thermally and can also be catalyzed by silver ions. [17] Complex 5 is indefinitely stable in the solid state at ambient temperature, and no noticeable decomposition was observed after exposure of the solid to atmospheric oxygen for a period of several days. In refluxing benzene, however, 5 was converted cleanly and quantitatively (measured by 1 H NMR spectroscopy) to iridabenzene 6.…”

Section: Resultsmentioning

confidence: 99%

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Synthesis, Characterization, and Isomerization of an Iridabenzvalene

Gilbertson

Weakley

Haley³

2000

Chem. Eur. J.

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Metal- halogen exchange of vinylcyclopropene 4 followed by addition of [(Me3P)2Ir(CO)Cl] produced iridabenzvalene 5. The metallabenzene valence isomer was characterized by NMR and IR spectroscopy and by X-ray crystallography. Isomerization of complex 5 to iridabenzene derivatives 6 and 13 was accomplished by thermolysis and by Ag+ ions, respectively. The former transformation was a clean and quantitative process that displayed first-order kinetics.

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Section: Resultsmentioning

confidence: 99%

“…The corresponding values for benzvalene (11) are 25.9 AE 0.2 kcal mol À1 and 1.6 AE 0.7 eu, respectively. [17] Figure 2. Time-evolved 1 H NMR spectra of the thermally promoted isomerization of 5 to 6 at 58.2 8C in [D 8 ]toluene.…”

mentioning

confidence: 99%

Synthesis, Characterization, and Isomerization of an Iridabenzvalene

Gilbertson

Weakley

Haley³

2000

Chem. Eur. J.

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“…For this barrier an experimental value of 25.9 kcalmol-has been found. [40] As it is extremely unlikely that sufficient excess energy will be available to cross an even higher barrier in the ground state it may be concluded that rearomatization to benzene is the only possible thermal isomerization reaction of benzvalene. The formation of fulvene from benzvalene can therefore be ruled out.…”

Section: Resultsmentioning

confidence: 99%

The photochemical Formation of Fulvene from Benzene via Prefulvene–a Theoretical Study

Dreyer

Klessinger

1996

Chemistry A European J

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Abstract:Results of semiempirical MN-DOC-CI and ab initio CASSCF calculations reveal that fulvene is a primary product of the photolysis of benzene. The photochemical step is assumed to lead to prefulvene, and both a synchronous conversion and a two-step process via bicyclo[3.1 .O]hexa-l,3-diene (isofulvene) could be ruled out as possible pathways from prefulvene to benzene. The most probable mechanism for the photochemi-and has to compete with the almost cal isomerization of benzene to fulvene in-barrierless formation of benzvalene and volves the intermediate structures pre-rearomatization to benzene. The shortfulvene and 1,3-~yclopentadienylcarbene lived intermediates are rather flexible structures with negligible barriers to inversion at the radical center in the threemembered ring of prefulvene and prebenzvalene and to rotation around the exocyclic single bond in 1,3-~yclopenta-dienyicarbene.

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“…( (4) durch thermische Isomerisierung aon 2: Man lost 1 .O g (4.0 mmol) 2 bei 25 'C in 20 ml entgastem, wasserfreiem Aceton und engt i. Wasserstrahlvak. 10) in ein NMR-Rohrchen filtriert und anhand eines NMR-Spektrums auf Reinheit gepriift.…”

Section: T E T R a C A R B O N Y L ( 3 4 -Q -T R I C~~~~/ 3 ~ O unclassified

Stufenweiser Abbau des Benzvalens in der Ligandensphäre eines Übergangsmetalls

Aumann

Wörmann

1979

Chem. Ber.

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Benzvalen (1) liefert bei Tieftemperaturphotolyse in Gegenwart von Fe(CO), den Fe(CO),-nKomplex 2. Dieser isomerisiert oberhalb 10°C rasch zum Acylkomplex 4 durch oxidative Addition einer auDeren Bindung der Bicyclobutan-Einheit. Die Protonierung von 2 erfolgt stereospezifisch endo auf der metallabgewandten Seite und ergibt den Fe(CO),-Komplex 3 des Bicyclo-[3.1.0]hexenyl-Kations, der bei -47 "C unter disrotatorischer Ringoffnung (AG' = 70.6 kJjmol) zum Fe(CO),-Cyclohexadienyl-Kation 6 zerfallt. Durch Markierungsexperimente wurde gezeigt, daR in 3 keine circumambulatorische Wanderung des Dreirings eintritt. -Die Protonierung von 4 fuhrt unter Spaltung der zweiten CC-Bindung zu einem neuartigen Acylium-Komplex 7, der bei Methanolyse den Ester 8 liefert. Beim ErwLrmen zerfallt 7 unter oxidativer Addition der dritten CC-Bindung zum kationischen Keten-Komplex 9, der bei Hydrolyse iiber einen Dihydroxyethen-Komplex 10 die Carbonsaure 11 ergibt. 11 kann durch Protonierung in FS03H iiber 10 wieder in 9 umgewandelt werden. -Bei Thermolyse von 4 entsteht ein LuRerst instabiler Ketenylkomplex 17, der durch Methanolyse abgefangen wurde. -Die thermische Metallierung von 1 mit Fe2(C0)9 verlauft im Prinzip wie oben dargestellt, jedoch konnen Zwischenstufen nicht isoliert werden, da diese zu Cyclopentadienyl-bzw. Fulvenkomplexen reagieren. Der Reaktionsverlauf wird anhand von Markierungsexperimenten diskutiert. Stepwise Degradation of Benzvalene in the Ligand Sphere of a Transition Metal ComplexOn low temperature photolysis in the presence ofFe(CO), benzvalene (1) gives a Fe(CO),-n-complex 2. At temperatures above 10°C 2 rearranges to an acyl complex 4 by oxidative addition of a CC bond of the bicyclobutane unit. Protonation of 2 occurs stereospecifically endo trans to the metal yielding the Fe(CO), complex 3 of the bicycl0[3.l.O]hexenyl cation which decomposes at -47°C by disrotatory ring opening (AG* = 70.6 kJjmol) to give cyclohexadienyl-Fe(CO), cation 6 . A circumambulatory migration of the three-membered ring in 3 has been excluded by labeling experiments. -Protonation of 4 leads to opening of the second CC bond to give a novel type of acylium complex 7, which on methanolysis affords the endo ester 8. On warming 7 reacts by an oxidative addition of the third CC bond yielding a ketene cation complex 9 quantitatively which on hydrolysis leads to the formation of the carboxylic acid 11 tiia a dihydroxyethene complex 10. On protonation of 11 with FS03H the reverse sequence 11 --f 10 + 9 can be achieved. -Thermolysis of 4 gives a rather unstable ketenyl complex 17 which can be trapped by methanolysis. -Thermal metalation of 1 with Fe2(C0)9 in principle follows the outlined path, but no intermediates can be isolated due to decomposition to cyclopentadienyl or fulvene complexes. The reaction course is discussed following results of labeling experiments.Benzvalen (l), ein Valenzisomeres des Benzols, wurde bereits 1937 von Hiickel diskutiert ') und 30 Jahre spater durch Photolyse von Benzol erstmals erhalten 'I. 1971 be-

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Kinetics and thermochemistry of the rearrangement of benzvalene to benzene. An energy sufficient but non-chemiluminescent reaction

Cited by 47 publications

References 12 publications

Synthesis, Characterization, and Isomerization of an Iridabenzvalene

Synthesis, Characterization, and Isomerization of an Iridabenzvalene

The photochemical Formation of Fulvene from Benzene via Prefulvene–a Theoretical Study

Stufenweiser Abbau des Benzvalens in der Ligandensphäre eines Übergangsmetalls

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