Reactivity and mechanism in oxidative addition to palladium(II) and reductive elimination from palladium(IV) and an estimate of the palladium-methyl bond energy

Journal Article · Wed Jun 01 04:00:00 EDT 1988 · Organometallics; (United States)

DOI:https://doi.org/10.1021/om00096a021· OSTI ID:7003506

Byers, P K; Canty, A J; Crespo, M; Puddephatt, R J; Scott, J D

Oxidative addition of MeI to (PdMe/sub 2/(bpy)) (bpy = 2,2'-bipyridine) occurs by the S/sub N/2 mechanism. Evidence includes the observation of second-order kinetics in acetone solvent, with a large negative value for the entropy of activation, and the observation of a cationic species, (PdMe/sub 3/(bpy)(CD/sub 3/CN))/sup +/I/sup -/, in CD/sub 2/CD solvent. The reaction occurs more slowly than the analogous reaction of (PtMe/sub 2/(bpy)), but the same mechanism operates. Reductive elimination from (PdIMe/sub 3/(bpy)) to give ethane and (PdIMe(bpy)) follows good first-order kinetics, occurs more rapidly in polar solvents, and is strongly retarded by added iodide. These observations are interpreted in terms of a mechanism that involves preliminary ionization of iodide followed by reductive elimination from the cation (PdMe/sub 3/(bpy))/sup +/. Studies by differential scanning calorimetry allow an estimate of the Pd-C bond energy of approx. 130 kJ mol/sup -1/ to be obtained, and this value is considerably higher than the activation energy for reductive elimination of ethane from (PdIMe/sub 3/(bpy)). The reductive elimination step is therefore concerted, and possible mechanisms, which may involve direct C-C coupling or C-C coupling after an agostic CHPd interaction, are discussed. This work is relevant to catalytic C-C coupling reactions using palladium complex catalysts.

• Research Organization: Univ. of Tasmania, Hobart (Australia)
• OSTI ID: 7003506
• Journal Information: Organometallics; (United States), Journal Name: Organometallics; (United States) Vol. 7:6; ISSN ORGND
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ACETONE
ACTIVATION ENERGY
AZINES
BIPYRIDINES
CATALYSTS
CHEMICAL BONDS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMPLEXES
DATA
ELEMENTS
ENERGY
EXPERIMENTAL DATA
HALOGENATED ALIPHATIC HYDROCARBONS
HETEROCYCLIC COMPOUNDS
INFORMATION
IODINATED ALIPHATIC HYDROCARBONS
KETONES
KINETICS
METHYL IODIDE
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN
PALLADIUM COMPLEXES
PYRIDINES
REACTION KINETICS
REDUCTION
TRANSITION ELEMENT COMPLEXES