The polymerization of 2-butene and its copolymerization with ethylene have been investigated using four kinds of dichlorobis(beta-diketonato)titanium complexes, [ArN(CH2)(3)NAr]TiCl2 (Ar=2,6-(Pr2C6H3)-Pr-i) and typical metallocene catalysts. The obtained copolymers display lower melting points than those produced of homopolyethylene under the same polymerization conditions. C-13 NMR analysis indicates that 9.3 mol-% of 2-butene units were incorporated into the polymer chains with Ti(BFA)(2)Cl-2-MAO as the catalyst system. With the trans-2-butene a higher copolymerization rate was observed than with cis-2-butene. A highly regioselective catalyst system for propene polymerization, [ArN(CH2)(3)NAr]TiCl2 complex using a mixture of triisobutylaluminium and Ph3CB(C6F5)(4) as cocatalyst, was found to copolymerize a mixture of 1-butene and trans-2-butene with ethylene up to 3.1 mol-%. Monomer isomerization-polymerization proceeds with typical metallocene catalysts to produce copolymers consisting of ethylene and 1-butene.