Ans reactions in aprotic solvents using metal-amine complexes as nucleophilic entity: experimental and theoretical studies

C.E.S. ALVARO; F. BERGERO; S.B. RAMOS; N. NUDELMAN

Concón

Conferencia; 14th. Latin American Conference on Physical Organic Chemistry; 2017

Pontificia Universidad Católica de Chile

Coordination complexes haveapplications invery diverse scientific and technological fields. Amine complexes exhibit a differentialreactivity with respect to free amines depending on, among other factors, themetal center character and the ligand structure. Studies of the AromaticNucleophilic Substitution (ANS) mechanism reported in the literature are mainlycentered on the nature of substrates, nucleophile basicity and solventpolarity, and the study of coordination complexes as a nucleophilic entity arescarce. The present work describes kinetic studies performed in toluene with1-chloro-2,4-dinitrobenzene (DNClB) and Cu (II) and Fe (II) complexes withaliphatic bifunctional amines such as ethylenediamine (EDA) and N,N-dimethylpropylamine (DMPA), previously studied in our laboratory in its non-complexedform1. They were chosen considering their characteristics of bi- dentateligands and the possible size of the metalo-cycle formed. Purification of thesolvent, reagents and substitution products1 in addition to thesynthesis and characterization of the complexes2 were performedusing procedures previously reported. The pseudo-first kY, and second order rate constants, kA,were calculated and a differential kA behavior was observedfor the metal-amine complexes as the complex concentration increased.Considering the self-aggregation of amines in aprotic solvents, these resultssuggest a different lability of the complexed amines attributed tostereo-electronic effects, to form free amine dimers that would react with thesubstrate. In order to interpret kinetic results by means of theoretical calculations, as a first step we performed Density FunctionalTheory calculations to determine the equilibriumstructure and itscorresponding formation energy in vacuum for complexes of Cu (II) and Fe (II)with EDA. These calculations were done at the B3LYP/6-31++G(d,p) and LANL2DZ level, and considering one to three ligands. Preliminary resultsindicate that the most stable complexes are those with three amines for both Cu(II) and Fe (II) complexes, and the Cu (II) ones are more stable than those ofFe (II). These resultswill be correlated with those obtained experimentally. Furthercalculations are currently in progress to consider also DMPA complexes and to includethe contribution of the basis set superposition errors (BSSE) to thestabilization energies.References1 C. E. S.Alvaro, N. S. Nudelman, Phys. Chem., Special Issue: Chemical Kinetics,2013, 3(2),39-47.2 G. M.El-Subruit, G. O. Younes, F. S. Zeitouni, M. F. Amira, Int. J. Chem. Kinet.,2008, 40(7), 416-422.