The invention provides a method for the preparation of a metallocene halide salt having at least one cyclopentadiene group substituted by a basic group, the method comprising reacting together a metal halide with a cyclopentadiene substituted by a basic group. In a preferred embodiment, the substituted cyclopentadiene is substituted with an amino group and the metal halide titanium tetrachloride. The invention provides a single step process for the preparation of metallocene derivatives which are useful in the formulation of medicaments and as polymerisation catalyst precursors.