Abstract: Active radicals produced by photolysis of substituted zirconocene dichloride complexes (RC₅H₄)₂ZrCl₂(R=H,CH₃,C₃H₇,C₄H₉,C₅,H₁₁,C₆H₁₁) and hafnocene dichloride complexes(RC₅H₄)₂HfCl₂(R=CH₃,C₂H₅, C₃H₇)were studied by combining spin trapping technique with ESR spectroscopy.The results show that the photolytic mechanisms of substituted zirconocene and hafnocene dichloride complexes are the same as those of titanocene dichloride complexes. In other words the primary process of photolysis is homolytic cleavage of the M-(RC₅H₄) (M=Ti, Zr, Hf)π bond. Only in the former case the free radicals RCpMCl₂(M=Zr, Hf) can be trapped by PBN and ND.

Key words: Spin trapping technique, Zirconocene Complex, ESR