Summary: Norbornene (NB) was oligomerized at 0 °C using AlEt2Cl‐TiCl4 at a monomer/titanium molar ratio of about 11. The oligomerization product consists of a fraction soluble in diethyl ether, amorphous by X‐ray examination, and of a crystalline fraction, insoluble in diethyl ether. The crystalline fraction was shown by powder X‐ray diffraction to consist of a NB heptamer. Single‐crystal X‐ray analysis indicated that the heptamer had a stereoregular 2,3‐exo‐disyndiotactic structure. The heptamer adopts a strained, highly irregular, folded conformation in the crystalline state. Structural differences with respect to NB oligomers obtained with zirconocene catalysts are discussed.A view of the molecular structure of the crystalline NB heptamer.magnified imageA view of the molecular structure of the crystalline NB heptamer.

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