Synthesis and characterisation of quinonide bridged dinuclear complexes of titanium and zirconium

Abstract

Cyclopentadienyl-zirconium(IV) and -titanium(IV) halides and alkyls react with hydroquinones to give bridged dinuclear complexes. Such compounds are also formed upon treatment of titanium(III) precursors with benzoquinone. Various cyclopentadienyl derivatives were used [cyclopentadienyl (C₅H₅), pentamethylcyclopentadienyl (C₅Me₅), ethyltetramethylcyclopentadienyl (C₅Me₄Et) and trimethylsilylcyclopentadienyl (C₅H₄SiMe₃)]. Several synthetic routes are described leading to the products [{Zr(C₅H₅)₂Cl}₂(µ-OC₆H₄O)]1a, [{Zr(C₅H₅)₂Cl}₂{µ-O(C₆H₃Bu^t-2)O}]1b, [{Zr(C₅H₅)₂Cl}₂{µ-O(C₆H₂Bu^t₂-2,5)O}]1c, [{Zr(C₅Me₄Et)₂Cl}₂(µ-OC₆H₄O)]1d, [{Ti(C₅Me₄Et)Cl₂}₂(µ-OC₆H₄O)]2, [{Ti(C₅Me₅)₂Cl}₂(µ-OC₆H₄O)]3, [{Ti(C₅Me₅)F₂}₂{µ-O(C₆H₂Bu^t₂-2,5)O}]4, [{Zr(C₅Me₄Et)₂F}₂(µ-OC₆H₄O)]5, [{Ti(C₅Me₅)₂F}₂(µ-OC₆H₄O)]6a, [{Ti(C₅H₄SiMe₃)₂F}₂(µ-OC₆H₄O)]6b, [{Ti(C₅Me₅)Me₂}₂{µ-O(C₆H₂Bu^t₂-2,5)O}]7 and [{Ti(C₅Me₅)Cl₂}₂O]8. Furthermore it is shown that the formation of the monobridged products is independent of the steric requirements of the substituents of the quinonide ring. The structures of [{Zr(C₅Me₄Et)₂Cl}₂(µ-OC₆H₄O)]1d and [{Ti(C₅Me₅)₂Cl}₂(µ-OC₆H₄O)]3 were solved by X-ray diffraction analysis.