Physical Organic Chemistry of Transition Metal Carbene Complexes. 19.1 Kinetics of Reversible Alkoxide Ion Addition to Substituted (Methoxyphenylcarbene)pentacarbonylchromium(0) and (Methoxyphenylcarbene)pentacarbonyltungsten(0) in Methanol and Aqueous Acetonitrile

摘要: Rate and equilibrium constants for the nucleophilic addition of MeO- in methanol 90% MeCN−10% MeOH, HC⋮CCH2O- CF3CH2O- 50% MeCN−50% water, OH- water (rate only) to Fischer carbene complexes type (CO)5MC(OMe)C6H4-4-Z (M = Cr W) are reported. The reactions lead formation tetrahedral adducts (CO)5M−C(OMe)(OR)C6H4-4-Z. kinetics general acid catalyzed loss from by phenol, 4-bromophenol, 3,5-dichlorophenol, regenerate complex, were also investigated. Hammett ρ ρn values as well approximate βnuc ( ) determined. They suggest that transition state alkoxide ion is imbalanced sense charge delocalization into CO ligands lags somewhat behind C−O bond formation. This finding consistent with fact intrinsic rate these substantially lower than those addi...