Studies on ansa-zirconocene-butadiene derivatives

The new compounds [Zr{Me2C(eta-C5H4)(2)}(cis-eta-C4H6)] (2*), [Zr{Me2C(eta- C5H4)(2)}Ph-2] (3), [Zr{Me2C(C5H4)(2)}(cis-eta(4)-C4H4Me2)] (4*), [Zr{Me2C( eta-C5H4)(2)}(cis-eta(4)-PhC4H4Ph)] (5), [Zr{Me2C(eta-C5H4)(2)Cl}(2)-mu-O] (6*), [Zr{Me2C(eta-C5H4)(2)}{eta(3)-C4H6B(C6F5)(3)}] (7), [Zr{Me2C(eta-C5H4 )(2)}{exo-eta(3)-C4H6B(C6F5)(3)}PMe3] (8*), [Zr{Me2C(eta-C5H4)(2)}{endo-eta (3)-C4H6B(C6F5)(3)}C6H5N] (9*), and [Zr{Me2C(eta-C5H4)(2)}{endo- and exo-et a(3)-C4H6B(C6F5)(3)}(NCBu)-Bu-t] (10a) and (10b) have been prepared. An ast erisk indicates the crystal structure has been determined. The photoelectro n spectra of 2 and 4 have been determined and assigned with the assistance of density functional methods. The factors relating to the relative stabili ty of cis- and trans-butadiene structures for 2 and 4 are discussed.