COMPETING NUCLEOPHILIC DISPLACEMENT AND RADICAL CHAIN REDUCTION IN REACTIONS OF TRANSITION-METAL HYDRIDE ANIONS WITH ALKYL BROMIDES 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, CE||HURD, PW||DARENSBOURG, MY||NEWCOMB, M

publication date

  • May 1987