Concerted Pathway to the Mechanism of the Anilinolysis of Bis(N,N-diethylamino)phosphinic Chloride in Acetonitrile

The kinetics of the nucleophilic substitution reactions of bis(N,N-diethylamino)phosphinic chloride with substituted anilines (XC6H4NH2) and deuterated anilines (XC6H4ND2) are investigated in MeCN at 65.0°C. The deuterium kinetic isotope effects (DKIEs) are secondary inverse (kH/kD < 1: 0.706–0.947) and the magnitudes of the secondary inverse DKIEs (kH/kD) increase constantly as the nucleophiles are changed from weakly basic to strongly basic anilines. The magnitudes of the selectivity parameters are ρX(H) = –6.34, and βX(H) = 2.24 with substituted anilines and ρX(D) = –6.13 and βX(D) = 2.17 with deuterated anilines. A concerted SN2 mechanism involving predominant backside attack is proposed based on the kH/kD values with substituent X.