Kinetics and Mechanism of the Reactions of Bis(acetylacetonato)-palladium(II) with Alkylamines

The reactions of bis(acetylacetonato)palladium(II), Pd(acac)2, with alkylamines (L) such as butyl-, cyclohexyl-, diethyl-, and dipropylamines in methanol to afford [Pd(acac)L2](acac) obey the usual two-term rate law, rate=(k0+k1[L])[Pd(acac)2]. On the other hand, the rate of reaction of Pd(acac)2 with diethylamine in THF and benzene is expressed by rate=(k1+k2[L])[L][Pd(acac)2]. A mechanism is proposed which presumes the hydrogen-bonding interaction of Pd(acac)2 with methanol and amine. Intermediacy of Pd(acac)(acac-C3)L in these reactions was denied on the basis of the kinetic studies, and the carbon-bonded complex was concluded to be produced via [Pd(acac)L2](acac). The equilibrium constants for the reactions, Pd(acac)2+2Et2NH[Pd(acac)(Et2NH)2(acac) and Pd(acac)(acac-C3)(Et2NH)+Et2NH[Pd(acac)(Et2NH)2](acac) were determined in dichloromethane and methanol.