Chemical compound, method for the production thereof and its use in catalyst systems for producing polyolefins

A catalyst system comprising

• A) at least one organometallic transition metal compound,
• B) at least one compound of formula IV
• wherein R20 are identical or different and are each halogen atoms, a hydrogen atom, C1–C20-alkyl, C1–C20-haloalkyl, C6–C20-aryl, C6–C20-haloaryl, C7–C40-arylalkyl, C7–C40-haloarylalkyl, C7–C40-alkylaryl or C7–C40-haloalkylaryl,
• C) at least one support component and
• D) at least one compound of formula I
• wherein
• M1 is boron,
• x is 4,
• y in 2,
• A is nitrogen
• R1 are identical or different and are each C6–C40-haloaryl, C6–C40-aryloxy, C7–C40-arylalkyl, C7–C40-haloarylalkyl, C7–C40-haloalkylaryl or C4–C40-cycloalkyl,
• R2 are identical or different and are each C1–C6-alkyl,
• R3 is C7–C20-arylalkyl, or
• R3 is C3–C9-cycloalkyl which may be substituted by C1–C20-alkyl, C1C20haloalkyl, C1–C10-alkoxy, C6–C40-haloaryl, C7–C40-alkylaryl, C7–C40-arylalkyl, C7–C40-haloarylalkyl or C7–C40-haloalkylaryl, and
• R4 is a hydrogen atom.