Group 4 permethylpentalene complexes as polymerisation catalysts

The primary aims of this thesis were to: (1) prepare new permethylpentalene complexes and to investigate their performance as homogeneous and heterogeneous α-olefins polymerisation catalysts, (2) investigate the polymerisation of polar monomers and (3) discover new (hydro)permethylpentalene catalysts for the Ring Opening Polymerisation (ROP) of lactide monomers. The thesis begins by offering an introduction to the chemistry of pentalene and its metal derivatives including ligand synthesis, organometallic chemistry and catalytic performances. The application of Cp*TiCl3 (Cp* = -C5Me5) and Pn*(H)TiCl3 (Pn*H = 5-C8Me6H) as olefin polymerisation catalysts, in both solution phase and immobilised on an insoluble methylaluminoxane (sMAO) support is described. Very high activities are observed for the styrene polymerisation using the supported Pn*(H)TiCl3. The systems were able to produce atactic polystyrene as well as high density polyethylene (HDPE). The ethylene/styrene copolymerisation ability of the catalysts is then demonstrated. A negative comonomer effect is described as well a low styrene incorporation. A variety of polymerisation conditions were studied, including the effects of temperature, styrene volume and solvent. Polymerisation of para-functionalised styrenes was studied using Cp*TiCl3 and Pn*(H)TiCl3. Para-functionalised styrenes containing electron donating groups NR2 (R = H, Me) and OMe lead to very high activities whereas the catalysts perform poorly in the presence of the electron-withdrawing substituent, Br. It was found that Cp*TiCl3 and Pn*(H)TiCl3 exhibited some of the highest activities for para-aminostyrene polymerisation reported in literature. Copolymerisations of 4-NR2-styrene with ethylene were attempted but no reaction occurred after poisoning of the catalyst by the comonomer. The (hydro)permethylpentalene titanium alkoxide and aryloxide complexes, Pn*(H)TiCl2(OR) were tested as ethylene and styrene polymerisation catalysts in solution and slurry phases. Pn*(H)TiCl2(O-Si(Me)2tBu) exhibited high styrene homopolymerisation activities in both phases. The three pre-catalysts tested produced high molecular weight polyethylene (Mw > 106 g/mol) but were unable to copolymerise other olefins. These complexes were also found to be initiators for the ROP of lactide. The kinetics of polymerisation, rates, effect of temperature, initiator concentration are discussed. The polymers were characterised by a range of physical methods to determine the tacticity, molecular weights and chain end groups. Finally, eight amidinate permethylpentalene complexes (Pn*ZrCl1–x[(NR’)2CR”]x) were prepared and investigated as slurry phase olefin polymerisation catalysts. Electronic and steric effects were studied by varying the amidinate substituents. Overall, low homopolymerisation activities were observed and these catalysts were unable to copolymerise ethylene with styrene and 4-NH2-styrene. The thesis concludes with experimental details and all characterisations performed as appendices.