[2,]zirconium dichloride (5), bearing methyl substituents on the carbons adjacent to a bridgehead carbon, was synthesized by key steps of the catalytic Pauson-Khand reaction and the retro-Diels-Alder reaction. The crystal structure of 5 was determined. The small angle (117.15°) between the two centroids of the cyclopentadienyls and a zirconium atom and the absence of any substituents on the positions with respect to the bridgehead carbon indicate that the coordination site for catalysis is widely opened. Compound 5, when activated with MAO, showed good performance for copolymerization of ethylene with a bulky monomer such as norbornene. The activity and norbornene incorporation ability are much better than those of [Ph 2 C(Fluo)(Cp)]ZrCl 2 .

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Keywords: Cyclopentadienyl / Zirconium / Titanium / Polymerization / Homogeneous catalysis sp 3 -C 1 -Bridged Cp/amido titanium and zirconium complexes are synthesized by using novel fulvenes that have substituents in the 1-, 4-, and 6-positions only. Thus, the nucleophilic attack of lithium tert-butylamide on 1,4-dimethyl-6-phenylfulvene, 6-(2-furyl)-1,4-dimethylfulvene and 6-cyclohexyl-1,4-dimethylfulvene, and subsequent aqueous workup, yields tBuN(H)−CHR−C 5 H 3 Me 2 (R = phenyl, 6; R = 2-furyl, 7; R = cyclohexyl, 8) in 80, 88, and 60% yields, respectively. The reactions of the ligands with M(NMe 2 ) 4 (M = Ti or Zr) afford the desired bis(dimethylamido) complexes, which can be transformed by treatment with Me 2 SiCl 2 to the dichloride complexes, (1,3-Me 2 C 5 H 2 −CHR−NtBu−κN)MCl 2 (M = Ti, R = phenyl, 10; M = Zr, R = phenyl, 11; M = Ti, R = 2-furyl, 13;

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