In this work,the systems of cobalt compounds-aluminum alkyls were used in the polymerization of butadiene to study the catalytic acdvity and the microstructure of the polymers.The results showed: (1) The catalytic system of cobalt complex of the outer orbital type
such as CoX2Py,(RC00)2CoPy,cobalt acetylacetonate,etc.with (i-C4H9)2AlCl,(C2H5)2AlCl and (C2H5)2AlBr,is highly active for polymerizing butadiene;however,it can not form a stereospecific catalyst with(C2H5)2AlI.The content of cis-1,4-structure is higher then 92%. (2) The activity of the system of inner orbital type cobalt complex with (i-C4H9)2AlCl,(C2H5)2AlCl,and (C2H5)2AlBr is lower than the outer orbital type
but the catalyst has nO remarkable eftect oil the microstructure of poly-mers. (3) The order of the substituent halogen in R2AlX for increasing average mole-culer weight of the polymer products is Cl>Br>I. (4) At a definite mole ratio of H2O:(i-C4H9)3Al or C2H5AlCl2 it forms with CoCl2·4C5H5N a highly active stereo-specific catalyst for the polymerization of butadiene.The results were analysed and dis-cussed.