A New Versatile Approach to Substituted Cyclopentadienyl−Cycloheptatrienyl Complexes of Zirconium (Trozircenes)

The reactions of Zr(C7H7)(Cl)(tmeda) (tmeda = N,N,N′,N′-tetramethylethylene-1,2-diamine) with cyclopentadienyl and substituted cyclopentadienyl anions have led to the expected Zr(C7H7)(C5H4R) and Zr(C7H7)(C9H7) complexes (R = H, CH3, SiMe3, C3H5 (allyl), PPh2; C9H7 = indenyl). The R = H and PPh2 complexes had previously been reported, but their preparations were accompanied by lower yields, among other drawbacks. The approach reported herein thus appears to offer a fairly general, effective, and convenient method for the preparation of zirconium complexes containing the C7H7 and a variety of monoanionic ligands. Structural data have been obtained for the R = CH3, SiMe3, and allyl species, as well as the indenyl complex. These data are consistent with previous conclusions that the zirconium center is present in a formal +4 oxidation state. Despite the 16-electron configurations for these species, the R = allyl complex showed no coordination of this substituent. As an apparent result of the hard nature of Zr(IV), weak THF coordination to the R = SiMe3 complex was observed to take place, via a structural study. Structural data were also obtained for the previously characterized Zr(C7H7)(C5H5){CN[2,6-C6H3(CH3)2]} complex.