Abstract

Fathia M. Helmy

Coordination chemistry of Co(ll) chloride dissolved in non aqueous formic acid in a series of concentrations upto very dilute solutions at 30°C are studied. The complexes have been detected by the changes in colour from blue to pink or vice versa. In general, the complexes of Co(ll) in most solvents are characterized by colour of solutions as well as by the shape and band maxima of the visible spectra. The visible spectra of the blue colour solutions indicate the presence of trichioro tetrahedral complex [CoCI3(HCOOH ] only. There is no evidence for the presence of dichloro complex [CoCI2(HCOOH)2] and the tetrachloro complex [CoCI4]2. The visible spectra of the pink colour solutions indicate the presence of octahedral complexes through their band maxima accompanied by extinction coefficient higher than the normal due to the overlapping of the band maxima of both tetrahedral and octahedral complexes. Also these complexes detected through a broad isobestic point at the band maximum which defined the octahedral complex formations. The interrelation between different complexes may be formed with the change in concentration is suggested.

concentrations; octahedral complexes; extinction

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