Borohydrido Rare Earth Complexes as Precatalysts for the Polymerisation of Styrene

Borohydrido based lanthanide complexes associated with n‐butylethylmagnesium are efficient catalytic systems for the polymerisation of styrene. The reaction is quantitative at 50 °C after several hours. Two growing chains per magnesium atom can be evidenced, and chain transfer between the lanthanide and the magnesium atoms may occur. The activity of such catalytic systems is found to be related to the nature of the rare earth metal.