Syntheses of titanium μ-arylimido and μ-pyridylimido complexes bearing (un)substituted cyclopentadienyl ligand

The reactions of (η5-C5H4CH2CH2Br)TiBr3, (η5-C5H4CH2CH2OCH3)TiCl3, (η5-C5H4-CH2-cyclo-C4H7O)TiCl3 and (η5-C5H5)TiCl3 with an equivalent of 2-MeOC6H4NHLi in the presence of Et3N afford μ-arylimido complexes, [(η5-C5H4CH2CH2Br)Ti(Br)(μ-NC6H4OCH3-2)]2 (1), [(η5-C5H4CH2CH2OCH3)Ti(Cl)( μ-NC6H4OCH3-2)]2 (2), [(η5-C5H4-CH2-cyclo-C4H7O)Ti(Cl)(μ-NC6H4OCH3-2)]2 (3), [(η5-C5H5)Ti(Cl)(μ-NC6H4OCH3-2)]2 (4), which include intramolecular titanium and oxygen coordination. Complex 4 can also be obtained by reaction of the (η5-C5H5)2TiCl2 with 2-MeOC6H4NHLi. Meanwhile refluxing of (η5-C5H5)2TiCl2 with an equivalent of 2-Me2NC6H4NMg·THF in toluene gives another μ-arylimido complex, [(η5-C5H5)Ti(Cl)(μ-NC6H4NMe2-2)]2, which contains intramolecular titanium and nitrogen coordination. In addition, the analogous reactions of the above substituted half-sandwich Cp titanium complexes with PhNHLi in the presence of Et3N lead to [(η5-C5H4CH2CH2Br)Ti(Br)(μ-NPh)]2, [(η5-C5H4CH2CH2OCH3)Ti(Cl)(μ-NPh)]2. The addition of 2-MeC6H4NHLi to (η5-C5H4CH2CH2OCH3)TiCl3 and (η5-C5H5)TiCl3 affords imido derivatives [(η5-C5H5)Ti(Cl)(μ-NC6H4CH3-2)]2 and [(η5-C5H4CH2CH2OCH3)Ti(Cl)(μ-NC6H4CH3-2)]2. [(η5-C5H5)Ti(Cl)(μ-NC6H3Me2-2,6)]2 is prepared by refluxing of (η5-C5H5)TiCl3 and 2,6-Me2C6H3NMg·THF in toluene. The titanium μ-pyridylimido complexes, [(η5-C5H5)Ti(Cl)(μ-NPy-2)]2, [(η5-C5H4CH2CH2OCH3)Ti(Cl)(μ-NPy-2)]2 and [(η5-C5H4CH2CH2Br)Ti(Br)(μ-NPy-2)]2, are synthesized by reactions of the above corresponding half sandwich Cp titanium complexes with an equivalent of 2-PyNHLi in the presence of Et3N, respectively. Compound 1 crystallizes in the triclinic space group P1̄ (no. 2) with a=9.942(2), b=10.057(3), c=8.457(2) Å, α=111.28(2), β=106.71(2), γ=98.12(2)°, V=725.5(4) Å3, Z=2. The catalytic activity and selectivity of compound 4 for the styrene polymerization is also investigated.