- Intermolecular electron-transfer reactions involving hydrazines
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The self-exchange electron-transfer (ET) rate constant k22 for 1,2,3,4,5-pentamethylferrocene was determined by NMR line broadening to be 8.5(±0.8) × 106 M-1 s-1 (25 °C, CD3CN/0.09 M Et4NBF
- Nelsen, Stephen F.,Chen, Ling-Jen,Ramm, Michael T.,Voy, Gilbert T.,Powell, Douglas R.,Accola, Molly A.,Seehafer, Troy R.,Sabelko, Jobiah J.,Pladziewicz, Jack R.
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p. 1405 - 1412
(2007/10/03)
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- PROTON-DRIVEN DIELS-ALDER REACTION OF AZO COMPOUNDS WITH CYCLIC DIENES
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Diels-Alder addition of bicyclic azo compounds to cyclic dienes would produce bis-N,N'-bicyclic hydrazines, but this reaction proves to be endothermic.The greater basicity of the adduct than of the azo compound makes the addition reaction 13.6-14.1 kcal mol-1 less endothermic (in water) if the protonated azo compound is employed instead of the neutral compound, and the addition reactions proceed well in acetonitrile if HBF4*Et2O is used to protonate the azo compound before adding the diene.Preparations of the neutral hydrazines derived from 2,3-diazabicyclooct-2-ene (5)with 1,3-cyclohexadiene (6) and from 2,3-diazabicyclohept-2-ene (10) with 6 and 1,3-cycloheptadiene (7, 11, and 13, respectively) as well as the saturated hydrazines derived by catalytic hydrogenation (9, 12, and 14, respectively) are reported.The neutral adduct of 10H(1+) and cyclopentadiene, 15, proves to be too thermally unstable for isolation, and the saturated form, 16, is prepared by diimide reduction of 15H(1+).The neutral hydrazines all give radical cations and dications with appreciable solution lifetimes, and 9(2+) (BF4(1-))2 is the first isolable hydrazine dication.The thermodynamics of electron loss for these hydrazines are studied by cyclic voltammetry, and prove to be dominated by non-bonded steric interactions between the alkyl groups.Compound 9 is the most easily oxidized hydrazine known, at E0' = -0.54 V vs SCE.
- Nelsen, Stephen F.,Blackstock, Silas C.,Frigo, Timothy B.
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p. 1769 - 1778
(2007/10/02)
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