Synthesis, Characterization of Tertiaryphosphine Cobalt (III) Complexes with Unsymmetrical NNOS Coordination Spheres and Their Thermodynamic Studies with Aliphatic Amines

Some new cobalt(III) complexes: [Co(Chel)(PBu3)]ClO4.H2O (where Chel: cdsalen, cd5OMesalen, cd5Brsalen, cd5Clsalen, cd5NO2salen, cdMesalen, cdPhsalen) and cdsalen = {methyl-2-[N-[2-(2-phenolate)methylidynenitrilo] ethyl}aminato(-1)-1-cyclopentenedithiocarboxylate; cd5OMesalen = {methyl-2-[N-[2-(5-methoxy-2-phenolate) methylidynenitrilo]ethyl}aminato(-1)-1-cyclopentenedithiocarboxylate; cd5Brsalen = {methyl-2-[N-[2-(5-bromo-2- phenolate)methylidynenitrilo]ethyl}aminato(-1)-1-cyclopentenedithiocarboxylate; cd5Clsalen = {methyl-2-[N-[2-(5- chloro-2-phenolate)methylidynenitrilo]ethyl}aminato(-1)-1-cyclopentenedithiocarboxylate; cd5NO2salen = {methyl-2- [N-[2-(5-nitro-2-phenolate)methylidynenitrilo]ethyl}aminato(-1)-1-cyclopentenedithiocarboxylate; cdMesalen = methyl-2-{N-[2-(2-hydroxyphenyl)ethylidynenitrilo]ethyl}amino-1-cyclopentenedithiocarboxylate and cdPhsalen = methyl-2-{N-[2-(2-hydroxyphenyl)phenylidynenitrilo]ethyl}amino-1-cyclopentenedithiocarboxylate were synthesized and characterized using elemental analysis, 1H NMR and IR spectra. The formation constants and the thermodynamic parameters were measured spectrophotometrically for 1:1 adduct formation of [Co(Chel)(PBu3)]ClO4.H2O (where Chel: cdsalen, cd5OMesalen, cd5Brsalen, cd5Clsalen, cd5NO2salen, cdMesalen, cdPhsalen) as acceptors with some aliphatic amines such as n-butylamine, sec-butylamine, tert-butylamine, benzylamine, dibutylamine and diethylamine as donors, in 98% methanol solvent and in constant ionic strength (I = 0.1 M NaClO4) and at various temperatures T = 283 to 313 (K) by using Ketelaar and van’t Hoff equations. The trend of the reactivity of the donors (amines) toward a given cobalt(III) Schiff base complex is as follow: n-butylamine > benzylamine > sec-butylamine > tert-butylamine > diethylamine > dibutylamine. Also, the comparison of formation constants and the thermodynamic parameters show that the trend of formation constants of five-coordinate cobalt(III) Schiff base complexes toward a given donor is as follows: cd5OMesalen > cdsalen > cd5Brsalen > cd5Clsalen > cd5NO2salen and cdMesalen > cdsalen > cdPhsalen.