**3.4 In efficient gadolinium metallocene-based catalyst for the synthesis of isoprene rubber with perfect 1,4-cis microstructure and marked reactivity difference between lanthanide metallocenes toward dienes as probed by butadiene−isoprene copolymerization catalysis**

An efficient gadolinium metallocene-based catalyst for the synthesis of isoprene rubber with perfect 1,4-Cis microstructure and marked reactivity difference between lanthanide metallocene toward dienes as probed by butadiene-isoprene copolymerization catalysis was studied. The large difference in catalytic reactivity effected by various lanthanide metals have been investigated by means of butadiene/isoprene copolymerization. It was observed that only the Gd-metallocene complex, which was the smallest and takes isoprene most reluctantly in the copolymerization with butadiene, can catalyze the homopolymerization of isoprene efficiently. The copolymerization reactions were carried out with varying initial monomer feed ratios at room temperature [18].
