β-Hydrogen-Containing Zirconium Alkyls with the Doubly-Bridged Bis(dimethylsilanediyl)dicyclopentadienyl Ligand. X-ray Molecular Structures of [Zr{(SiMe2)2(η5-C5H3)2}ClEt] and [Zr{(SiMe2)2(η5-C5H3)2}Et]2(μ-CH2CH2)

Alkylation of [Zr(CpSi 2 Cp)Cl 2 ] (CpSi 2 Cp = (η 5 -C 5 H 3 ) 2 [Si(CH 3 ) 2 ] 2 with 1 equiv of RMgCl in THF at 10 °C gave the monoalkylated complexes [Zr(CpSi 2 Cp)ClR] (R = Et, n-Pr, i -Pr) in 80% yield, the isopropyl complex isomerizing to the n -propyl derivative above 10 °C. Addition of a second equivalent or an excess amount of the akylating agent resulted in the formation of the dialkyl compounds [Zr(CpSi 2 Cp)R 2 ] (R = Et, n-Pr). Hydrolysis of [Zr(CpSi 2 Cp)ClR] led to the μ-oxo dinuclear complex [{Zr(CpSi 2 Cp)Cl} 2 (μ-O)]. Thermal decomposition of THF solutions of [Zr(CpSi 2 Cp)ClR] takes place with the evolution of an equimolar amount of alkane and alkene and the formation of [Zr(CpSi 2 Cp)Cl 2 ] and an unidentified residue. Formation of [Zr(CpSi 2 Cp)Et 2 ] is always accompanied by decomposition with the evolution of ethane to give [{Zr(CpSi 2 Cp)Et} 2 (μ-CH 2 CH 2 )] in 70% yield. A similar behavior was observed for [Zr(CpSi 2 Cp)(n-Pr) 2 ]. All of the compounds were characterized by elemental analysis and NMR spectroscopy, and the molecular structures of [Zr(CpSi 2 Cp)ClEt] and [{Zr(CpSi 2 Cp)Et} 2 (μ-CH 2 CH 2 )] were studied by X-ray diffraction methods. Density functional calculations on the model compound [{ZrCp 2 Me} 2 (μ-CH 2 CH 2 )] satisfactorily reproduce d C - C = 1.482, d 1 Zr - C = 2.327 Å, and d 2 Zr-C = 2.506 Å, the geometry found experimentally.