Kinetic role of t-amines in the ligand inhibited osmium tetraoxide catalyzed trimethylamine-N-oxide dihydroxylation of alkenes

Erdik E., KAHYA N. D.

TRANSITION METAL CHEMISTRY, cilt.28, sa.6, ss.658-664, 2003 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 28 Sayı: 6
  • Basım Tarihi: 2003
  • Doi Numarası: 10.1023/a:1025435708610
  • Dergi Adı: TRANSITION METAL CHEMISTRY
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.658-664
  • Ankara Üniversitesi Adresli: Evet

Özet

Kinetic studies on the t-amine inhibited catalytic OsO4 dihydroxylation of cyclooctene, octene, styrene and 4-methyl-, 4-methoxy-, 4-chloro-, 4-(chloromethyl), 4-(trifluoromethyl) and 3-chloro-derivatives of styrene with Me3NO in t-BuOH have been carried out at 50 degreesC. The reactions follow identical kinetics: first order in total osmium species, first order in Me3NO and zero order in alkene. All t-amines have been found to retard the catalysis and the reaction order in t-amine changes from inverse first order to zero. The involvement of dioxomonoglycolataosmium(VI) esters and their monoamine adducts in the rate-determining oxidation step was established by the linear plots of 1/Deltak(2) versus. 1/[L] where Deltak(2) is the decrease in second order rate constant in the presence of [L] concentration of t-amine ligand. Beyond a definite concentration of t-amine, the rate reaches a minimum and remains constant. Activation parameters were evaluated for catalytic OsO4 dihydroxylation of 4-(chloromethyl)styrene at different t-amine concentrations. The values of DeltaH(.) and DeltaS(.) are consistent with the proposed mechanism.