Tandem catalysis using group 5 and 6 imido complexes and group 4 permethylindenyl catalysts

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Complexes known as constrained geometry catalysts (CGC) of the form R2Si(C5R'4)(R''N)MX2 are of great interest for the synthesis of polyethylene; both industrially and scientifically. Furthermore, in recent years, the O'Hare group have synthesised a number of novel metallocenes based on group 4 permethylindenyl (I*) complexes for use as ethylene polymerisation catalysts.Ethylene oligomerisation, generating higher alpha-olefins from ethylene, is as the forefront of industrial research. This includes the Dimersol, Alphabutol and Phillips trimerisation processes. Work within the O'Hare group has shown that tungsten imido complexes to be extremely active and selective towards the ethylene dimerisation to 1-butene in both the solution and slurry phase. Recently niobium imido complexes of the form Nb(CHSiMe3)(NAr)(OC(CF3)3)(PMe3)2 (Figure 2(b)) were found to be active towards the ring opening metathesis polymerisation of norbornene.Tandem catalysis involves the cooperative action of two or more catalysts to afford a product that is not accessible by the individual catalyst alone. There have been a number of reported tandem catalytic systems reported in the literature, both in solution, and more recently in the heterogeneous phase. Karbach and co-workers developed a silica-supported system that allowed incorporation of 1-hexene into at polymer chain.Ethylene polymerisation catalysts - the aim of this part of the project is to synthesise new group 4 constrained geometry I* complexes of the general formula R12SB(R2N,I*)MX2 with intention of developing them into commercial viable ethylene polymerisation catalysts. Ethylene oligomerisation catalysts - the aims of this project include the synthesis of niobium and tantalum imido complexes of the form M(NAr)Cl3.THF, M(NAr)Me2Cl and the solid supported equivalents. These complexes will then be developed into commercially viable ethylene oligomerisation catalysts for higher alpha-olefins, in particular 1-octene or 1-butene with high selectivity.Tandem catalysis - the final aim is to simultaneously support both an ethylene polymerisation and an oligomerisation catalyst on a solid support, such as polymethylaluminoxane, in order to form LLDPE from a single ethylene feed source.This project falls within the EPSRC Physical Sciences research area. In particular this project focuses on catalysis with the aim to develop new catalysts for ethylene polymerisation and oligomerisation.