The directed oligomerization of propene and 1-hexene was carried out with a series of CP'(C5H5)ZrCl2 and Cp'2ZrC2, pre-catalysts (Cp' = C5HMe4, C4Me4P, C5Me5, C(5)H(4)tBu(2), C5H2-1,3-'Bu-2, C5H2 -1,2,4-'Bu-3) together with (C5H5)(2)ZrCl2, Oligomers in the molar mass range 300-1500 g/mol for propene and 200-3000 g/mol for 1-hexene were synthesized at 50degreesC. The majority of oligomer molecules contain a double-bond end group. Oligomer characterization was carried out by gel permeation chromatography (GPC), H-1 and C-13 NMR. Vinylidene double bonds (front beta-hydrogen elimination) are solely found for the tert-butyl-substituted zirconocenes and for most of the unsymmetrical methyl-substituted CP'(C5H5)ZrCl2 systems (except Cp' = phospholyl). With (C4Me4P)(C5H5)ZrCl2 and with the symmetrical methyl-containing Cp'2ZrCl2 pre-catalysts, also vinyl end groups (from P-methyl elimination) are observed in the case of oligopropenes. The vinylidene/vinyl ratio depends on the ligand and the vinyl content increases from C5HMe4 (65/35) over C4Me4P (61/39) to C5Me5 (9/91). The phospholyl zirconocenes and (C5HMe4)(2)ZrCl2, also exhibit chain-transfer to aluminum thereby giving saturated oligomers. (C) 2002 Elsevier Science B.V. All rights reserved.