Polymerization of propylene by silylene- and germylene-bridged group 4 metallocenes

In order to compare with silylene-bridged group 4 metallocenes, C-2 symmetric dimethylgermylene-bridged zirconocene and hafnocene dichlorides were prepared and employed as the catalyst for polymerization of propylene in combination with methylaluminoxane (MAO). Germylene-bridged metallocenes always produced isotactic polypropylene of higher molecular weight than that produced by silylene-bridged analogues. The molecular structures of four metallocenes prepared from dimethylsilylene and germylenebis(2,3,5-trimethylcyclopentadienyl) were detemined by X-ray diffraction and showed no substantial differences of geometry between silylene- and germylene-bridged ones.