beta-Hydrogen-containing zirconium alkyls with the doubly-bridged bis(dimethylsilanediyl)dicyclopentadienyl ligand. X-ray molecular structures of [Zr{(SiMe2)(2)(eta(5)-C5H3)(2)}ClEt] and [Zr{(SiMe2)(2)(eta(5)-C5H3)(2)}Et](2)(mu-CH2=CH2)

Alkylation of [Zr(CpSi2Cp)Cl-2] (CpSi2Cp = (eta(5)-C5H3)(2)[Si(CH3)(2)](2) with 1 equiv of RMgCl in THF at 10 degrees C gave the monoalkylated complexes [Zr(CpSi2Cp)ClR] (R = Et, n-Pr, i-Pr) in 80% yield, the isopropyl complex isomerizing to the n-propyl derivative above 10 degrees C. Addition of a second equivalent or an excess amount of the akylating agent resulted in the formation of the dialkyl compounds [Zr(CpSi2Cp)R-2] (R = Et, n-Pr). Hydrolysis of [Zr(CpSi2Cp)ClR] led to the mu-oxo dinuclear complex [{Zr(CpSi2Cp)Cl}(2)(mu-O)]. Thermal decomposition of THF solutions of [Zr(CpSi2Cp)ClR] takes place with the evolution of an equimolar amount of alkane and alkene and the formation of [Zr(CpSi2Cp)Cl-2] and an unidentified residue. Formation of [Zr(CpSi2Cp)Et-2] is always accompanied by decomposition with the evolution of ethane to give [{Zr(CpSi2Cp)Et}(2)(mu-CH2=CH2)] in 70% yield. A similar behavior was observed for [Zr(CpSi2Cp)(n-Pr)(2)]. All of the compounds were characterized by elemental analysis and NMR spectroscopy, and the molecular structures of [Zr(CpSi2Cp)ClEt] and [{Zr(CpSi2Cp)Et}(2)(mu-CH2=CH2)] were studied by X-ray diffraction methods. Density functional calculations on the model compound [{ZrCp2Me}(2)(mu-CH2=CH2)] satisfactorily reproduce d(C-C) = 1.482, d1(Zr-C) = 2.327 Angstrom, and d2(Zr-C) = 2.506 Angstrom, the geometry found experimentally.