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

Abstract

The reactions of (η 5-C 5H 4CH 2CH 2Br)TiBr 3, (η 5-C 5H 4CH 2CH 2OCH 3)TiCl 3, (η 5-C 5H 4-CH 2- cyclo-C 4H 7O)TiCl 3 and (η 5-C 5H 5)TiCl 3 with an equivalent of 2-MeOC 6H 4NHLi in the presence of Et 3N afford μ-arylimido complexes, [(η 5-C 5H 4CH 2CH 2Br)Ti(Br)(μ-NC 6H 4OCH 3-2)] 2 ( 1), [(η 5-C 5H 4CH 2CH 2OCH 3)Ti(Cl)( μ-NC 6H 4OCH 3-2)] 2 ( 2), [(η 5-C 5H 4-CH 2- cyclo-C 4H 7O)Ti(Cl)(μ-NC 6H 4OCH 3-2)] 2 ( 3), [(η 5-C 5H 5)Ti(Cl)(μ-NC 6H 4OCH 3-2)] 2 ( 4), which include intramolecular titanium and oxygen coordination. Complex 4 can also be obtained by reaction of the (η 5-C 5H 5) 2TiCl 2 with 2-MeOC 6H 4NHLi. Meanwhile refluxing of (η 5-C 5H 5) 2TiCl 2 with an equivalent of 2-Me 2NC 6H 4NMg·THF in toluene gives another μ-arylimido complex, [(η 5-C 5H 5)Ti(Cl)(μ-NC 6H 4NMe 2-2)] 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 Et 3N lead to [(η 5-C 5H 4CH 2CH 2Br)Ti(Br)(μ-NPh)] 2, [(η 5-C 5H 4CH 2CH 2OCH 3)Ti(Cl)(μ-NPh)] 2. The addition of 2-MeC 6H 4NHLi to (η 5-C 5H 4CH 2CH 2OCH 3)TiCl 3 and (η 5-C 5H 5)TiCl 3 affords imido derivatives [(η 5-C 5H 5)Ti(Cl)(μ-NC 6H 4CH 3-2)] 2 and [(η 5-C 5H 4CH 2CH 2OCH 3)Ti(Cl)(μ-NC 6H 4CH 3-2)] 2. [(η 5-C 5H 5)Ti(Cl)(μ-NC 6H 3Me 2-2,6)] 2 is prepared by refluxing of (η 5-C 5H 5)TiCl 3 and 2,6-Me 2C 6H 3NMg·THF in toluene. The titanium μ-pyridylimido complexes, [(η 5-C 5H 5)Ti(Cl)(μ-NPy-2)] 2, [(η 5-C 5H 4CH 2CH 2OCH 3)Ti(Cl)(μ-NPy-2)] 2 and [(η 5-C 5H 4CH 2CH 2Br)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 Et 3N, 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) Å 3, Z=2. The catalytic activity and selectivity of compound 4 for the styrene polymerization is also investigated.