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 monoalkylat ed complexes [Zr(CpSi2Cp)ClR] (R = Et, n-Pr, i-Pr) in 80% yield, the i sopropyl complex isomerizing to the n-propyl derivative above 10 degre es C. Addition of a second equivalent or an excess amount of the akyla ting agent resulted in the formation of the dialkyl compounds [Zr(CpSi 2Cp)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 decompositio n 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(C pSi2Cp)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 beha vior was observed for [Zr(CpSi2Cp)(n-Pr)(2)]. All of the compounds wer e characterized by elemental analysis and NMR spectroscopy, and the mo lecular structures of [Zr(CpSi2Cp)ClEt] and [{Zr(CpSi2Cp)Et}(2)(mu-CH2 =CH2)] were studied by X-ray diffraction methods. Density functional c alculations on the model compound [{ZrCp2Me}(2)(mu-CH2=CH2)] satisfact orily reproduce d(C-C) = 1.482, d1(Zr-C) = 2.327 Angstrom, and d2(Zr-C ) = 2.506 Angstrom, the geometry found experimentally.