The aminolysis of phosphinates; the kinetics and mechanism of the aminolysis of phosphinate esters in acetonitrile

The aminolysis of aryl diphenylphosphinates, p-nitrophenyl diphenylphosphinothionate, -phosphinothioate, and -phosphinodithioate by n-butylamine, by the secondary amines piperidine, pyrrolidine, morpholine, and dipropylamine, as well as by a series of diamines, has been studied in acetonitrile. The general reactivity order is diamines > butylamine > sec-amines. Butylaminolysis follows a two-term rate law, one first order in amine and the other second order in amine. The second order in amine term predominates. sec-Amines and diamines follow a rate law which is first order in amine only. Leaving group effects, solvent effects, and activation parameters support a pathway which involves rate-determining collapse of a zwitterionic pentacoordinate intermediate. In the case of butylamine this collapse is general base catalyzed and for the diamines the reaction is intramolecularly general base catalyzed.