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EPR/ENDOR detection of stable titanium(III) and titanium(IV) radical products generated by single electron transfer from (iso-PrO)3TiCH3

, and . Journal of the Chemical Society, Perkin Transactions 2: Physical Organic Chemistry, (1992)

Abstract

Single-electron-transfer reactions between the stereoselective carbanion source methyltriisopropoxytitanium(IV) as donor and a-diimines, ketones, or a-dicarbonyls as p acceptor substrates exhibit a dichotomy with respect to the ESR-detectable paramagnetic 'escape' products. Substrates with very neg. redn. potentials such as 2,2'-bipyridine yield Ti(III) species, whereas more easily reducible mols. such as dinucleating 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine react to yield ESR-detectable Ti(IV) complexes of the corresponding anion radicals. A very stable paramagnetic product was isolated from the reaction between 3,5-di-tert-butyl-o-quinone (dtbq) and (Me2CHO)3TiMe; this first thermally stable, but apparently configurationally labile, Ti(IV) semiquinone complex (dtbq-1)Ti(OCHMe2)3.bul. was studied by UV-VIS-NIR absorption and ESR/ENDOR spectroscopy. on SciFinder(R)

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