Retta, Negussie (PhD)Kebede, Zerihun2018-06-272023-11-092018-06-272023-11-091988-06http://etd.aau.edu.et/handle/12345678/4226The dichlorotetrapyridineCobalt(lll) complexes ~co(PY)4C12 ~ X(X = Cl- , N~-, 01° 4 -, 1° 4 -, SCN-, N~-) were synthesized and oharacterized by using elemental analysis and speotroscopio techniques. The spectral data for complexes in the UV, Vis ("'" ~.../ J- I ), and IR ( \t (Co-Cl), V(Co-N» regions have been determined. From conduotivity measurement equivalent conductivity at infinite dilution ( ~) and association constants (KA) were estimated in various solvents. " Non-linear oorrelation of the association conetant of the medium has been shown. Larger assooiation constants for 104- and SCN-, whereas lower association constants for NO~- and Cl- salts were found. Rates of aquation of the complexes were measured in water as a function of Co-solvents (50:50); (v/v), and with the different composition of ethanol; and faster rate of aquations were Observed for SCN- and NO~- and slower for 104- oounter ions. The nuoleophilic order of the oounter ions of the complexes was also established. The increasing order of the nuoleophilicity of the oounterions was found as follows:SON- < No-3 < CI< CIO4 –C<N-3enCo(py) 4Cl2Thesis