J. Iran. Chem. Soc., Vol. 8, No. 3 September 2011, pp.794~802.

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Kinetics, Mechanism and Synthesis of Adduct Formation of Tetraaza Schiff Base Cobalt(ΙΙ) Complexes as Donor with Diorganotin(IV)dichlorides as Acceptor

Z. Asadi, M. Asadi* and F. Mosalanezhad

Chemistry Department, College of Sciences, Shiraz University, Shiraz, 71454, Iran

The kinetics and mechanism of the adduct formation of diorganotin(IV)dichlorides (R2SnCl2), where R = Ph, Me, Bu, with Co(II) tetraaza Schiff base complexes such as: [Co(appn)]{[N,N'-1,2-propylenebis(o-amino-α-phenylbenzylideneiminato) cobalt(ΙΙ)]} and [Co(cappn)]{[N,N'-1,2-proylenebis(5-chloro-o-amino-α-phenylbenzylideneiminato)cobalt(II)]}, were studied spectrophotometrically. The kinetic parameters and the rate constant values show the acceptor tendency trend for the diorganotin(IV)dichlorides as follows: Ph2SnCl2 > Me2SnCl2 > Bu2SnCl2. Adducts were separately synthesized and fully characterized by 119Sn NMR, 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 decreased as follows: Co(appn) > Co(cappn). The linear plots of kobs vs. the molar concentration of the diorganotin(IV)dichlorides, the high span of the second order rate costant k2 values and the large negative values of ΔS suggest an associative (A) mechanism for the acceptor-donor adduct formation. Moreover, [Co(aptn)]{[N,N'-1,3-propylenebis-(o-amino-α-phenylbenzylideneiminato)cobalt(ΙΙ)] and [Co(captn)]{[N,N'-1,3-proylenebis-(5-chloro-o-amino-αphenylbenzylideneiminato)cobalt(II)]} were synthesized and characterized but, their kinetics with R2SnCl2 were so fast that it was impossible to follow them using the conventional methods.

Keywords: Diorganotin(IV)dichlorides, Kinetic, Mechanism, Tetraaza Schiff base, Cobalt(II) complex

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