Abstract: In hydrochloric acid, the dimolybdenum (V)-cysteine complexes, Na₂Mo₂O₂ (μ₂-X)(μ₂-Y)(cysteine)₂,(X=Y=oxygen(Ⅰ);X=oxygen,Y=sulfur(Ⅱ), give an ESR signal at 1.947, the strength of the signal increases with the enhancement of the concentration of hydrochloric acid. The complex (Ⅲ), Na₂Mo₂O₂ (μ₂-S)₂(cysteine)₂, gives an analogous signal only in concentrated acid. By comparing the data of magnetic susceptibility and electron spectrum, the dissociation mechanism of the complexes in hydrochloric acid is assumed and the chemical stability of the complexes affected by bridged atoms is also discussed.

Key words: Dimolybdenum (V)-cysteine complexes, ESR, Dissociation