Electron Donor-Acceptor Complexes. 1. Linear Free Energy Correletion of the Charge-Transfer Transition Energy with the Kinetics of Halogenolysis of Alkylmetals

Article abstract of DOI:10.1021/j100455a007

Mulliken charge-transfer theory is used to relate the properties of transient donor-acceptor complexes between alkylmetals and halogens with the kinetics of the accompanying cleavage reaction (halogenolysis).The formulation derives from the charge-transfer transition energy hν_CT which is proportional to the second-order rate constant for halogenolysis of a variety of tetraalkyltin compounds in hexane or carbon tetrachloride solutions.The description of the activation process for halogenolysis as an electron transfer in the CT complex, e.g., --> , leads to a linear free energy relationship in which the activation free energy is equal to the driving force for ion pair formation.The latter is equated to the charge-transfer transition energy plus a contribution from the solvation energy, by employing a comparative procedure for the evaluation of alkylmetals.An independent measure of the solvation energy obtained from the gas-phase ionization potentials of alkylmetals and their free energy changes in solution supports the electron-transfer formulation of the activation process.The charge-transfer mechanism is generalized for the halogenolysis of alkylmetals.