Equilibrium Studies of α-Diimine Displacement in Cationic Allylpalladium(II) Complexes by Monodentate N-Donors and the Mechanism of Allyl Amination by Triethylamine and Pyridine

Article abstract of DOI:10.1039/DT9940003113

In the cationic complexes 3-allyl)(L-L)>ClO4 the chelated α-diimine was rapidly and reversibly displaced by secondary amines (N-methylaniline, morpholine or piperidine), triethylamine and 4-substituted pyridines.The observed equilibrium constants K_e increased with increasing basicity and decreasing steric requirements of the entering N-donor.They strongly depend on the α-diimine and decrease in the order RN=CHCH=NR <*> RN=C(Me)C(Me)=NR ca.NC5H4(CH=NR)-2 (R = C6H4OMe-4).The cationic complex 3-C3H5)>(1+) underwent a slow allyl amination by triethylamine or pyridine (L') in the presence of fumaronitrile (fn), yielding 2-fn)> and Et3N(1+)CH2CH=CH2 or C5H5N(1+)CH2CH=CH2.Kinetic studies showed that the pseudo-first order rate constants for amination (k_obs) are given by k_obs = k₂, suggesting a direct bimolecular attack of L' on the η³-allyl ligand.Amination hardly proceeds in the presence of the less-activated olefin dimethyl fumarate (dmf).The ?-accepting properties of the olefinic ligands play an important role also in the reaction of Et3N(1+)CH2CH=CH2 or C5H5N(1+)CH2CH=CH2 with 2-olefin)> (olefin = fn or dmf), i.e. the reverse of the amination reaction.

Full text of DOI:10.1039/DT9940003113

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