Competing nucleophilic displacement and radical-chain reduction in reactions of transition-metal hydride anions with alkyl bromides Academic Article uri icon

abstract

  • The reactions of group 6 metal hydrides, PPN+HM(CO)4L-(M = Cr, L = CO; M = W, L = CO, P(OMe)3), with two mechanistic probes, 6-bromo-l-hexene (1) and 4-bromo-3,3-dimethyl-1-butene (3), in THF at 25 °C were studied. Neopentyl-like probe 3 was reduced (presumably) exclusively by a radical chain process, and the second-order rate constants (kH) for hydrogen atom abstraction from HM(CO)4L- by the intermediate radical, 2,2-dimethyl-3-butenyl, were determined. Unhindered probe 1 was reduced by both an SN2 pathway and a radical chain process. The second-order rate constants for hydrogen atom abstraction from HM(CO)4L-by 5-hexenyl were estimated, and the percentages of reduction of 1 by the SN2 pathway and the radical chain process were calculated; the percentage of reduction by the SN2 pathway increased in the order HCr(CO)5- < HW(CO)5- < HW(CO)4P(OMe)3-. The combination of a hindered and an unhindered probe as used in this study has expanded the utility of mechanistic probes by permitting quantitation of competing pathways. © 1987, American Chemical Society. All rights reserved.

published proceedings

  • Journal of the American Chemical Society

author list (cited authors)

  • Ash, C. E., Hurd, P. W., Darensbourg, M. Y., & Newcomb, M

citation count

  • 34

complete list of authors

  • Ash, Carlton E||Hurd, Philip W||Darensbourg, Marcetta Y||Newcomb, Martin

publication date

  • May 1987