Stable rac-[1,2-Ethylene-1,1‘-bis(η5-tetrahydroindenyl)]- zirconacyclopentanes. Syntheses, X-ray Crystal Structures, Stability, and Catalysis of Ethylene Polymerization

The reaction of rac -(ebthi)Zr(η 2 -Me 3 SiC 2 SiMe 3 ) ( 1 ) [ebthi = 1,2-ethylene-1,1‘-bis(η 5 -tetrahydroindenyl)] with an excess of ethylene at room temperature leads to the corresponding zirconacyclopentane 3, which was isolated as stable yellow crystals and characterized by an X-ray crystal structure analysis. At 203 K complex 1 reacts with only 1 equiv of ethylene to form the zirconacyclopentene 2, possibly an intermediate in the reaction from 1 to 3 . Upon activation with tris(pentafluorophenyl)borane under an ethylene atmosphere, complex 3 was shown to be an effective catalyst for ethylene polymerization. The reaction of 2 equiv of styrene with the alkyne complex 1 leads to the unsymmetrically substituted zirconacyclopentane 6 .