title: Investigation of the [Sm(N(SiMe(3))(2))(2)] reducing system in THF. Rate and mechanistic studies.
abstract: The reductant [Sm(N(SiMe(3))(2))(2)] was examined by cyclic voltammetry and UV-vis spectroscopy. Rate constants and activation parameters for the reduction of 1-iodobutane, 2-butanone, and methylacetoacetate by [Sm(N(SiMe(3))(2))(2)] were measured in THF by stopped-flow absorption decay experiments. Comparison with SmI(2) and SmI(2)-HMPA shows that the redox potential of [Sm(N(SiMe(3))(2))(2)] is intermediate between the SmI(2)-based reductants, yet it reduces alkyl iodides and ketones at a faster rate than the powerful combination of SmI(2) and HMPA. The activation data for reduction of alkyl iodides and ketones by [Sm(N(SiMe(3))(2))(2)] are consistent with highly ordered transition states having low activation barriers. All of these results taken together suggest that the mechanism of reduction of alkyl iodides and ketones by [Sm(N(SiMe(3))(2))(2)] has more inner-sphere character than reduction by SmI(2) or Sm-(HMPA) complexes. The change in the ET mechanism is attributed to the unique structure of the [Sm(N(SiMe(3))(2))(2)] complex.
authors.affiliation: Contribution from the Department of Chemistry and Biochemistry, Texas Tech University, Box 41061, Lubbock, Texas 79409-1061.
authors.forename: Edamana
authors.initials: E
authors.lastname: Prasad
authors.forename: Brian W
authors.initials: BW
authors.lastname: Knettle
authors.forename: Robert A
authors.initials: RA
authors.lastname: Flowers