Catalysts for preparation of ultra high molecular weight polyethylene (UHMWPE) and process for preparation thereof

An olefin polymerization catalyst comprising a metal complex of Formula (I)

• wherein
• M is a transition metal atom of Group 3 to Group 11 of the periodic table;
• A is sulfonate (SO3) or carboxylate (CO2);
• when n=0, D=N═CH—or when n=1, D=N;
• X=Cl, Br, I, BF4, or OAc;
• and
• R, and R1 to R4 are the same or different, and are each a hydrogen atom, a halogen atom, a hydrocarbon group, a heterocyclic group, an oxygen-containing group, a nitrogen-containing group, a boron-containing group, a sulfur-containing group, a phosphorus-containing group, a silicon-containing group, a germanium-containing group or a tin-containing group, and two or more of them may be bonded to each other to form a ring.