A series of bis(peralkylindenyl)zirconocene and hafnocene complexes were synthesised and characterised by NMR spectroscopy, mass spectrometry and elemental analyses.


We report the synthesis of two zirconocenes, dimethylsilylbis(hexamethylindenyl) zirconium dichloride, rac-(SBI*)ZrCl2, and nbutyldimethylsilyl(hexamethylindenyl) zirconium trichloride, [(Ind*SiMe2nBu)Zr(μ-Cl)Cl2]2. The complexes were characterised by NMR spectroscopy and X-ray crystallography, and the bonding was evaluated using density functional theory. 



Unsymmetrical permethylindenyl bent metallocene complexes have been synthesised and reacted with inorganic solid supports to afford catalysts for the slurry phase polymerisation of ethylene. Those supported on solid polymethylaluminoxane were both highly active catalysts and afforded polymers with a desirable, low aggregation, “popcorn” morphology.


Permethylindenyl constrained geometry complexes of the type Me2SB(RN,I*)TiCl2({(η5-C9Me6)Me2Si(RN)}TiCl2; R = i-Pr, t-Bu,n-Bu, Ph, 4-t-BuPh and 4-n-BuPh). Reaction with solid polymethylaluminoxane (sMAO) yields solid catalysts active for the slurry phase polymerisation of ethylene. 



Solid polymethylaluminoxane (sMAO) supported ansa-bridged permethylindenyl zirconocenes Me2SB(CpR,I*)ZrX2 ({(η5-C9Me6)Me2Si(η5-C5H3R)}ZrX2; R = H, Me, and nBu; X = Cl, Br, Me, and CH2Ph) have been investigated as catalysts for the slurry-phase polymerization of ethylene in the presence of H2. The catalysts demonstrated remarkable stability to H2 both in a high-throughput screening system and in a 2 L batch reactor, with an almost constant ethylene uptake maintained throughout the polymerization runs. The catalysts demonstrated very high ethylene polymerization activities, almost 3 times higher than sMAO-(CpnBu)2ZrCl2 (industrial standard zirconocene catalyst) under the same conditions. The presence of small quantities of H2 (<1%) led to significant decreases in polymer molecular weights to produce commercially desirable polyethylene waxes (Mn < 10 kg mol–1) in a batch reactor.



The synthesis and characterisation of constrained geometry scandium and aluminium permethylindenyl complexes Me2SB(RN,I*)ScCl(THF), Me2SB(iPrN,I*)Sc(O-2,6-iPr-C6H3)(THF), Me2SB(iPrN,I*)Sc(O-2,4-tBu-C6H3)(THF),Me2SB(nBuN,I*)Sc(O-2,6-iPr-C6H3)(THF), Me2SB(PhN,I*)Sc(O-2,6-iPr-C6H3)(THF), Me2SB(tBuN,I*)AlCl(THF), Me2SB(tBuN,I*)Al(O-2,6-Me-C6H3)(THF) and Me2SB(tBuN,I*)Al(O-2,4-tBu-C6H3)(THF) are reported. Ring-opening polymerisation of L- and rac-lactide using all complexes show first-order dependence on monomer concentration and produced polylactide with unimodal molecular weight distribution. 


Recent publications:

L  and rac-lactide polymerisation using scandium and aluminium permethylindenyl complexes, N. Diteepeng, I.A.P. Wilson, J.-C. Buffet, Z.R. Turner and D. O'Hare, Polym. Chem., (2020) 2020, 11, 6308 – 6318.

Metallocene polyethylene wax synthesis, J.V. Lamb, J.-C. Buffet, Z. R. Turner, T. Khamnaen, and D. O′Hare, Macromolecules, (2020),  53, 5847–5856. 

Ethylene polymerization using zirconocenes supported on pentafluorophenyl-modified solid polymethylaluminoxane, J.V. Lamb, J.-C. Buffet, Z.R. Turner and D. O′Hare, Macromolecules, (2020), 53(3), 929-935.

Slurry-phase ethylene polymerisation using group 4 ansa-bridged permethylindenyl complexes supported on polymethylaluminoxane, J.V. Lamb, J.C. Abell, J.E. McLaren, J.C. Buffet, Z.R. Turner and D. O'Hare, J. Mol, Catal., (2020) 484, p.110735.  

Group 4 constrained geometry complexes for olefin (co)polymerisation, Thomas J.Williams, Alexander D.H.Smith, Jean-Charles Buffet, Zoë R. Turner, Dermot O'Hare, Molecular Catalysis, (2020), 486, 110872. 

Constrained geometry scandium permethylindenyl complexes for the ring-opening polymerisation of L- and rac-lactide, N. Diteepeng, J.-C. Buffet, Z. Turner, D. O'Hare, Dalton Trans., (2019), 48, (42), 16099-16107.  

Group 4 permethylindenyl complexes for the polymerisation of L‑ and rac‑lactide monomers, J.V. Lamb, J.E. Matley, C.M.R. Wright, Z.R. Turner, J.‑C. Buffet and D. O'Hare, Dalton Trans., (2019), 48, 2510-2520. 

Group 4 permethylindenyl complexes for slurry-phase polymerisation of ethyleneJ.V. Lamb, J.-C. Buffet, Z.R. Turner and D. O'Hare, Polym. Chem., 2019, 10, 1386-1398.

Synthesis, characterisation and slurry phase ethylene polymerisation of rac-(PhBBI*)ZrClimmobilised on modified layered double hydroxides, G.E. Hickman, C.M.R. Wright, A. F.R. Kilpatrick, Z.R. Turner, J.-C. Buffet, D. O’Hare, Mol. Catal., (2019), 468, 139-147. 

Popcorn-shaped polyethylene synthesised using highly active supported permethylindenyl metallocene catalyst systems, J.-C. Buffet, Z. R. Turner and D. O’Hare, Chem. Commun. (2018), 54, 10970-10973.

Group 4 permethylindenyl constrained geometry complexes for ethylene polymerisation catalysis, T. J. Williams, J.-C. Buffet, Z. R. Turner and D. O’Hare, Catal. Sci. Technol. (2018).

Synthesis and Characterisation of Permethylindenyl zircononium Complexes and their use in ethylene polymerisation, J.-C. Buffet, T.A. Q. Arnold, P. Angpanitcharoen, Z. R. Turner, RSC Adv., (2015), 5, 87456-87464.

Synthesis, Characterisation, and Polymerisation Studies of Hexamethylindenyl Zirconocenes and Hafnocenes, T.A.Q. Arnold, J.-C. Buffet, Z.R. Turner and D. O’Hare, J. Organomet. Chem., (2015), 792, 55-56.