Intramolecular coupling of eta/sup 2/-iminoacyl groups at group 4 metal centers: a kinetic study of the carbon-carbon double-bond-forming reaction
The series of bis(eta/sup 2/-iminoacyl) compounds of general formula M(OAr)/sub 2/(eta/sup 2/-R'NCR)/sub 2/ (M = Ti, Zr, Hf; OAr = 2,6-diisopropyl- and 2,6-di-tert-butylphenoxide; R = CH/sub 3/, CH/sub 2/Ph; R' = various substituted phenyls) undergo intramolecular coupling on thermolysis to produce the corresponding enediamide derivatives M(OAr)/sub 2/(R'NC(R) = C(R)NR'). A kinetic study of the reaction in hydrocarbon solvents has shown it to be first order. The reaction is metal dependent with the rate decreasing in the order Ti > Zr > Hf. The rate of the reaction is also dependent on the steric and electronic nature of the nitrogen substituent (R'). The use of the bulky aryl group 2,6-dimethylphenyl retards the reaction, while the use of various 3- and 4-substituted phenyls (3-F, 3-OMe, 4-OMe, 4-Cl, 4-NMe/sub 2/) shows the reaction to be accelerated by electron-withdrawing substituents. A sigma plot based on kinetic data obtained at 67/sup 0/C and 77/sup 0/C yielded rho values of 0.83 (R = 0.97) and 0.84 (R = 0.95), respectively. Both the steric and electronic dependence of the reactivity on the nitrogen substituents is discussed mechanistically and used to rationalize the much more facile intramolecular coupling observed for the related eta/sup 2/-acyl (eta/sup 2/-OCR) functionalities.
- Research Organization:
- Purdue Univ., West Lafayette, IN (USA)
- DOE Contract Number:
- FG22-85PC80909
- OSTI ID:
- 7247375
- Journal Information:
- J. Am. Chem. Soc.; (United States), Vol. 110:5
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
HAFNIUM COMPOUNDS
CHEMICAL REACTIONS
ORGANIC NITROGEN COMPOUNDS
ORGANOMETALLIC COMPOUNDS
TITANIUM COMPOUNDS
ZIRCONIUM COMPOUNDS
ADDUCTS
BINDING ENERGY
CHEMICAL REACTION KINETICS
EXPERIMENTAL DATA
MEDIUM TEMPERATURE
DATA
ENERGY
INFORMATION
KINETICS
NUMERICAL DATA
ORGANIC COMPOUNDS
REACTION KINETICS
REFRACTORY METAL COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
400201* - Chemical & Physicochemical Properties