Compounds for use in catalyst compositions for the production of polyolefins

The present invention relates to compds. according to formula I wherein: .bul. each R1-​R10 may individually be H, a halogen, an alkoxy moiety, a siloxy moiety, a nitrogen-​contg. moiety, an alkyl moiety, an aryl moiety, or an aralkyl moiety, wherein each R1-​R10 comprises ≤ 10 carbon atoms, wherein each of R1-​R10 may form a cyclic moiety with an adjacent R1-​R10 moiety; .bul. Y is O or N-​R11, wherein R11 is an alkyl, cycloalkyl, aryl or aralkyl moiety comprising 1-​12 carbon atoms; .bul. M is a group 3 or 4 transition metal, preferably Ti, Zr or Hf, more preferably Ti; .bul. X is .bul. a sigma-​bonded ligand, for example: (i) a halogen, (ii) an amine, or (iii) a moiety wherein each X may contain 1 to 10 carbon atoms, selected from an alkyl moiety, an aralkyl moiety, an alkoxy moiety, and an aryloxy moiety; or .bul. a diene, for example a butadiene moiety or an isoprene moiety; .bul. z is the no. of ligands X that are bonded to M. Such compds. may be used in a catalyst system for olefin polymn., particularly ethylene copolymn., providing at least one of a high catalyst activity, a high comonomer incorporation, and​/or a high mol. wt. polymer.