JICS Online, Journal of the Iranian Chemical Society

Home About Editorial Board Instructions to Authors Subscription Archive Submission Feedback

Article info. : 2006; 3(3) (pp 247~252)

Donor Ligand, Basal Ligand and Solvent Effects on the Equilibrium Constants of Triphenylphosphinecobalt(III) Schiff Base Complexes with Phosphite Ligands

M. Asadi^a,*, K. Mohammadi^b and A.H. Kiyanfar^c

^{aChemistry Department,
College of Sciences, Shiraz University, Shiraz 71454, I.R. Iran

^bChemistry Department, Faculty of Sciences, Persian Gulf
University, Bushehr 75169, I.R. Iran

^cChemistry Department, College of Sciences, Kurdestan University,
Sanandaje, I.R. Iran

(Received 22 April 2006, Accepted 17 May 2006)

The equilibrium constants and the
thermodynamic parameters were spectrophotometrically measured for the 1:1
adduct formation of [Co(Salen)(PPh₃)]ClO₄.H₂O,
and [Co(7,7^’-Me₂Salen)(PPh₃)]ClO₄.H₂O
as acceptors, with P(OR)₃ (R = methyl, ethyl , and i-propyl) as
donors, in acetonitrile (CH₃CN) and dimethylformamide (DMF) as
solvents at constant ionic strength (I = 0.1 M NaClO₄), and
various temperatures (t = 10-50 °C). Our results revealed the following
trends: stability of the cobalt(III) Schiff base complexes toward a given
phosphite donor, [Co(7,7^'-Me₂Salen)(PPh₃)]⁺
< [Co(Salen)(PPh₃)]⁺; binding of the donors (phosphites)
toward a given cobalt(ΙΙΙ)
Schiff base complex, P(OEt)₃
> P(OMe)₃> P(O-ⁱPr)₃; influence of
solvent on the stability of a given cobalt(III) Schiff base complex toward a
given phosphite donor, CH₃CN < DMF.

Keywords:
Schiff base, Thermodynamic parameter, Equilibrium
constant, Phosphine, Cobalt complex}