Free-radical pathways to alkyl complexes of a nickel tetraaza macrocycle
The cationic nickel(I) macrocycle (1R,4S,8R,11S)-(1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane)nickel(I), abbreviated R,S,R,S-(Ni(tmc))/sup +/, reacts in aqueous, alkaline solutions on the stopped-flow time scale with alkyl halides to form a new series of organonickel complexes. Kinetic data were obtained for a large number of alkyl halides. The trends in the rate constants are benzyl > allyl > secondary > primary > methyl > cyclopropyl, and RI > RBr > RCl. These trends suggest that carbon-centered free radicals R are produced by a bimolecular reaction between Ni(tmc)/sup +/ and RX and are then captured by a second Ni(tmc)/sup +/. Further evidence for free-radical involvement comes from cyclization of the radical produced from 6-bromo-1-hexene, from the yields of products in those instances where dimerization of the free radical competes with its capture by Ni(tmc)/sup +/, and from the nonreactivity of alkyl tosylates. The organonickel complexes slowly hydrolyze in unimolecular processes to yield hydrocarbon and the nickel(II) complex R,S,R,S-(Ni(tmc))/sup 2 +/. The organonickel complexes do not undergo unimolecular homolysis but react with Co(II) macrocycles with a 1:2 stoichiometry to form cobalt-carbon bonds. This reaction most likely occurs not by homolytic displacement but by electron transfer followed by radical capture.
- Research Organization:
- Iowa State Univ., Ames
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 5058053
- Journal Information:
- Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 25:18; ISSN INOCA
- Country of Publication:
- United States
- Language:
- English
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Mechanistic investigation of carbon-carbon bond formation in the reduction of alkyl halides by organonickel complexes in aqueous solution. [R'X (R' = CH/sub 3/, C/sub 2/H/sub 5/, 1-C /sub 3/H/sub 7/, 2-C/sub 3/H/sub 7/, and PhCH/sub 2/; X = Cl, Br, I) RNi(tmc)/sup +/ (R = C/sub 2/H/sub 5/, C/sub 3/H/sub 7/, and CH/sub 2/-c-C/sub 5/H/sub 9/; tmc = (1R,4R,8S,11S)-1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane)]
Reactions of disubstituted alkanes with a nickel(I) macrocycle
Related Subjects
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
AQUEOUS SOLUTIONS
CATIONS
CHARGED PARTICLES
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
COMPLEXES
DATA
DISPERSIONS
EXPERIMENTAL DATA
INFORMATION
IONS
KINETICS
MIXTURES
NICKEL COMPLEXES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANOMETALLIC COMPOUNDS
PH VALUE
RADICALS
REACTION INTERMEDIATES
REACTION KINETICS
SOLUTIONS
SYNTHESIS
TRANSITION ELEMENT COMPLEXES