A 1:2 complex of MgCl2 and tetrahydrofuran (THF) was prepared by a simple Grignard decomposition reaction using Mg metal and 1,2-dichloroethane in THF as diluent. The MgCl2.2THF complex formed a homogeneous solution with titanium-n-butoxide in xylene at 60-degrees-C. The soluble Mg-Ti complex in xylene polymerized ethylene under homogeneous conditions in the presence of organoaluminium compounds. The kinetic behaviour of the polymerization reaction was studied. It was observed that the presence of MgCl2 transformed the Ti centre from a dimerization to a polymerization catalyst.