Facile cyclization of the valeronitrile group bound to a nickel macrocycle

Journal Article · Wed Aug 20 04:00:00 EDT 1986 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00277a055· OSTI ID:5469777

Bakac, A; Espenson, J H

The reduction of Br(CH/sub 2/)/sub 4/CN in alkaline, aqueous solution by the nickel(I) macrocycle (R,R,S,S)-Ni(tmc)/sup +/ yields the acyclic organonickel complex NC(CH/sub 2/)/sub 3/CH/sub 2/Ni(tmc)/sup +/ (lambda/sub max/ 394 nm, epsilon 2.0 x 10/sup 3/ M/sup -1/ cm/sup -1/). When 0.5-1 M H/sub 3/O/sup +/ is added immediately to the freshly prepared complex, it rapidly hydrolyzes to the acyclic product CH/sub 3/(CH/sub 2/)/sub 3/CN. If, on the other hand, the acyclic organonickel complex is allowed to stand in solution at pH 2-12, then cyclopentanone is the only organic product formed in approx. 100% yield. The values of the rate constants at 25/sup 0/C and activation parameters for the cyclizations of NC(CH/sub 2/)/sub 3/CH/sub 2/Ni(tmc)/sup +/ (k/sub c/ = 0.135 s/sup -1/, ..delta.. H double dager = 19.8 +/- 0.3 kcal mol/sup -1/, ..delta.. S = 4.0 +/- 1.0 cal mol/sup -1/ K/sup -1/) and the free radical/sup 26/ (k/sub c/ = 3.9 x 10/sup 3/ s/sup -1/, ..delta.. Hdouble dager = 8.0 kcal mol/sup -1/, ..delta.. S double dager = -15.2 cal mol/sup -1/ K/sup -1/) definitely show that these are two different processes. Indeed, the cyclizing entity in the nickel complex is probably best considered a nickel-bound carbanion. The main contributions to the activation enthalpy come from cyclization and the breaking of the Ni-C bond. The relatively high ..delta.. S double dager seems to indicate that cyclization occurs in concert with hydrolysis, eq 3, and not as an entirely intramolecular process with the transient formation of (CH/sub 2/)/sub 4/CNNi(tmc)/sup +/.

• Research Organization: Iowa State Univ., Ames
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 5469777
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 108:17; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400303* -- Organic Chemistry-- Isotope Exchange & Isotope Separation-- (-1987)
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMPLEXES
DATA
DEHYDROCYCLIZATION
ENTHALPY
ENTROPY
EXPERIMENTAL DATA
INFORMATION
KINETICS
MEDIUM TEMPERATURE
NICKEL COMPLEXES
NITRILES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHYSICAL PROPERTIES
RADICALS
REACTION INTERMEDIATES
REACTION KINETICS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPLEXES