Catalyst system for polymerisation of an olefin

A polyolefin formed by the process comprising:

• contacting an olefin with catalyst system to form the polyolefin, wherein the catalyst system comprises a Ziegler-Natta type procatalyst, a co-catalyst and at least one external electron donor, wherein the external electron donor comprises a compound having the structure according to Formula I:
• Si(L)n(OR11)4−n (Formula I),
• wherein,
• Si is a silicon atom with valency 4+;
• O is an oxygen atom with valency 2− and O is bonded to Si via a silicon-oxygen bond;
• n is 1, 2, 3 or 4;
• R11 is a selected from the group consisting of linear, branched and cyclic alkyl having at most 20 carbon atoms and aromatic substituted and unsubstituted hydrocarbyl having 6 to 20 carbon atoms;
• L is a group represented by the following structure
• wherein,
• L is bonded to the silicon atom via a nitrogen-silicon bond;
• L has a single substituent on the nitrogen atom, where this single substituent is an imine carbon atom;
• and
• X and Y are each independently selected from the group consisting of:
• a) a hydrogen atom;
• b) a group comprising a heteroatom selected from group 13, 14, 15, 16 or 17 of the IUPAC Periodic Table of the Elements through which X and Y are each independently bonded to the imine carbon atom of Formula II, wherein the heteroatom is substituted with a group consisting of a linear, branched and cyclic alkyl groups having at most 20 carbon atoms, optionally containing a heteroatom selected from group 13, 14, 15, 16 or 17 of the IUPAC Periodic Table of the Elements;
• and/or with an aromatic substituted and unsubstituted hydrocarbyl groups having 6 to 20 carbon atoms, optionally containing a heteroatom selected from group 13, 14, 15, 16 or 17 of the IUPAC Periodic Table of the Elements;
• c) a linear, branched and cyclic alkyl having at most 20 carbon atoms, optionally containing a heteroatom selected from group 13, 14, 15, 16 or 17 of the IUPAC Periodic Table of the Elements;
• and
• d) an aromatic substituted and unsubstituted hydrocarbyl having 6 to 20 carbon atoms, optionally containing a heteroatom selected from group 13, 14, 15, 16 or 17 of the IUPAC Periodic Table of the Elements.