Shohei Katao

Effect of ligand substituents in olefin polymerisation by half-sandwich titanium complexes containing monoanionic iminoimidazolidide ligands–MAO catalyst systems

Various half-sandwich titanium complexes containing iminoimidazolidide ligands, CpTiCl(2)[1,3-R(2)(CH(2)N)(2)C=N] (1a-d) [R = Ph (a), 2,6-Me(2)C(6)H(3) (b), cyclohexyl (c), (t)Bu (d)], have been employed as the catalyst precursors for ethylene polymerisation, syndiospecific styrene polymerisation, and copolymerisation of ethylene with 1-hexene in the presence of MAO cocatalyst; 1d showed the highest catalytic activity for ethylene polymerisation whereas 1b showed the highest activity for syndiospecific styrene polymerisation.

Synthesis, Structure, and Properties of α,β‐Linked Oligothiazoles with Controlled Sequence

α,β-Linked oligothiazoles with head-to-tail connectivity are presented as a new family of helical scaffolds. Combinations of palladium-catalyzed cross-coupling reactions at the 5- and 4-positions of 2-phenylthiazole led to the synthesis of oligo(2-phenylthiazoles) with ortho linkages with a variety of defined sequences. The secondary structures of the α,β-linked oligo(2-phenylthiazoles) showed a clear dependence on their sequences. X-ray crystallography of the trimer, tetramer, and hexamer with head-to-tail connection revealed the formation of a helical structure, which was stabilized by a combination of intramolecular forces, including interheteroatom (S⋅⋅⋅N), CH-π, and π-π interactions. The introduction of a chiral end-group successfully led to the induction of chirality into the helical conformations. Programmable sequences for controlled geometries and photofunctions have been demonstrated through the manifold connection pathways in α,β-linked oligothiazoles.

Synthesis of half-titanocenes containing 1,3-imidazolidin-2-iminato ligands of type, Cp*TiCl2[1,3-R2(CH2N)2CN]: highly active catalyst precursors in ethylene (co)polymerisation

A series of (pentamethylcyclopentadienyl)titanium(IV) dichloride complexes containing 1,3-imidazolidin-2-iminato ligands of type, Cp*TiCl2[1,3-R2(CH2N)2CN] [R = tBu (1a), cyclohexyl (Cy, 1b), C6H5 (1c), 2,6-Me2C6H3 (1d), 2,6-iPr2C6H3 (1e)] have been prepared and structures of 1b–e have been determined by X-ray crystallography. These complexes, especially 1d,e showed notable catalytic activities not only for ethylene polymerisation, but also for ethylene/1-hexene copolymerisation (activity 482 000–1 750 000 kg-polymer per mol-Ti per h) in the presence of MAO.