Polyolefin catalyst and use thereof

A complex, wherein said complex is formed by a compound of formula I and a divalent or trivalent metal salt, and the complex of the structure represented by following formula II:

• wherein,
• Y1 is C1-C8 alkyl, C1-C8 haloalkyl, or unsubstituted or substituted phenyl;
• Y2 is CR4R5, O or S, R4 and R5 are independently C1-C4 alkyl or haloalkyl;
• or Y1 and Y2, and the C—C bond attached to both of them together forms unsubstituted or substituted 5-12 member ring;
• together with Y3, is substituted 5-7 member monocyclic, or bicyclic or tricyclic group containing said 5-7 member monocyclic ring, wherein the 5-7 member monocyclic ring contains 1-3 N, O or S atoms, and contains at least one N;
• Y3 is one or more substituents on the 5-7 member monocyclic ring, or bicyclic or tricyclic group containing said 5-7 member monocyclic ring, at least one Y3 is halogen, C1-C8 alkyl, C1-C8 haloalkyl, unsubstituted or substituted phenyl, unsubstituted or substituted benzyl, —O—R7, —CH2—O—R8, —SR9, or —CH2—S—R10, wherein R7, R8, R9 and R10 are independently C1-C8 alkyl, or unsubstituted or substituted phenyl;
• Z is C1-C8 alkyl, C1-C8 haloalkyl, unsubstituted or substituted phenyl, or unsubstituted or substituted naphthyl, provided that Y1 and Z, and the C═N bond attached to both of them together do not form unsubstituted or substituted 5-12 member ring;
• wherein, the “substituted” in the above definitions means that the group possesses 1-5 substituents selected from the group consisting of C1-C4 alkyl, C1-C4 haloalkyl, halogen, nitro, cyano, CF3, —O—R1, —N(R2)2, —Si(R3)3, —CH2—O—R8, —SR9, —CH2—S—R10, —CH—(R10)2, and phenyl which is unsubstituted or substituted by 1-5 substituents selected from the group consisting of C1-C4 alkyl and C1-C4 haloalkyl, wherein R1, R2 and R3 are independently C1-C4 alkyl or haloalkyl;
• while R8, R9 and R10 are independently C1-C8 alkyl or phenyl;
• M is nickel or palladium;
• X is independently halogen, C1-C4 alkyl, C2-C6 alkenyl, allyl (), −OAc, −OTf, or benzyl.