Disclosed herein are methods of making bis(phenol) ligand compounds and transition metal bis(phenolate) compounds. The transition metal bis(phenolate) compounds can be used as components in catalyst systems for the polymerization of olefins.

The objectives of the present invention are to provide an olefin oligomerization catalyst that allows properties of particles of a polymer component by-produced in an -olefin production process to be obtained in such a shape that does not negatively affect a separation process for the particles and to provide a method for producing an olefin oligomer performed in the presence of the olefin oligomerization catalyst. The objectives can be achieved by the olefin oligomerization catalyst obtained by contacting (D) a transition metal compound with a preliminary contact solid catalyst component (II) obtained by contacting a solid catalyst component (I) formed by supporting (B) an organoaluminum oxy-compound (b-2) on (A) a solid carrier with (C) at least one compound selected from the group consisting of an organometallic compound (c-1), an organoaluminum oxy-compound (c-2), and a compound (c-3) that reacts with the transition metal compound (D) to form a pair of ion.