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Inne
Interconversion of conjugated and nonconjugated polyolefin cobalt complexes in two oxidation states : an electrochemical and NMR study.
Autorzy
Rok wydania
1986
Czasopismo
Journal of the American Chemical Society
Numer woluminu
108
Strony
7454-7461
DOI
10.1021/ja00284a002
Kolekcja
Język
Angielski
Typ publikacji
Artykuł
The kinetics of interconversion between the conjugated (1,3) and nonconjugated (1,5) isomers of cyclooctatetraene (cot) complexes of CpCo [Cp = C5H5] 1 and *CpCo [*Cp = C5Me5] 2 have been studied. Dynamic NMR studies were employed for neutral CpCo(cot) and gave a rate of 3 s'1 at 370 K, extrapolated to 4 X 10~3 s-1 at 298 K. The permethylated complex isomerizes more slowly, k = 3 X 10""4 s'1 at 370 K. However, fast fourier transform ac polarography results show that the monoanions of CpCo(cot) and *CpCo(cot) isomerize at the same fast rate, 2 X 103 s~* at 298 K. An explanation is offered in terms of the lifting of symmetry restrictions to the simplest molecular isomerization motion in the anion radicals. The dibenzocyclooctatetraene complex CpCo( 1,5-dbcot) (3) reduces to a stable anion which shows no tendency to isomerize. This is explained by a likely change in electronic ground states of [CpCo(cot)]™ and [CpCo(dbcot)]~, a conclusion supported by ESR results.
Adres publiczny
http://dx.doi.org/10.1021/ja00284a002
