Tungsten based catalyst system

摘要

A catalyst system including the combination of a source of tungsten; a ligand precursor containing at least N or O as a bonding atom to bond to the tungsten in the source of tungsten, the source of tungsten and the ligand precursor being selected to form an acid due to the bonding of the ligand precursor to the tungsten; and the catalyst system being characterized therein that it is substantially free of the acid formed due to the bonding of the ligand precursor to the tungsten; and that the molar ratio of the tungsten in the source of tungsten to ligand precursor is at least 1:3/n where n is the number of bonds that the ligand precursor forms with the tungsten.