Synthesis, Kinetics, and Mechanism for Adduct Formation of Tetraaza Schiff Base Cobalt(II) Complexes with Diorganotin(IV)dichlorides in Dimethylformamide Solvent

The kinetics and mechanism of the adduct formation of diorganotin(IV)dichlorides with Co(II) tetraaza Schiff base complexes, such as [Co(ampen)] {[N,N'-ethylenebis-(o-amino-alpha-phenylbenzylideneiminato)cobalt(II)]}, [Co(campen)] {[N,N'-ethylenebis-(5-chloro-o-amino-alpha-phenylbenzylideneiminato)cobalt(II)]}, and [Co(amaen)] {[N,N'-ethylenebis-(o-amino-alpha-methylbenzylideneiminato)cobalt(II)]}, were studied spectrophotometrically. The kinetic parameters and the rate constant values show the following acceptor tendency trend for the diorganotin(IV)dichlorides: Ph2SnCl2 > Me2SnCl2 > Bu2SnCl2. Adducts have been separately synthesized and fully characterized by (SnNMR)-Sn-119, IR, UV-vis spectra, and elemental microanalysis (C,H,N) methods. The trend of the rate constants for the adduct formation of the cobalt complexes with a given tin acceptor decreases as follow: Co(amaen) > Co(ampen) > Co(campen). The linear plots of k(obs) vs. the molar concentration of the diorganotin(IV)dichlorides, the high span of the second-order rate constant k(2) values, and the large negative values of AS(not equal) suggest an associative (A) mechanism for the acceptor donor adduct formation. (C) 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 499-507, 2010