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)

Abstract

Alkylation of [Zr(CpSi2Cp)Cl2] (CpSi2Cp = (η5-C5H3)2[Si(CH3)2]2 with 1 equiv of RMgCl in THF at 10 °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 °C. Addition of a second equivalent or an excess amount of the akylating agent resulted in the formation of the dialkyl compounds [Zr(CpSi2Cp)R2] (R = Et, n-Pr). Hydrolysis of [Zr(CpSi2Cp)ClR] led to the μ-oxo dinuclear complex [{Zr(CpSi2Cp)Cl}2(μ-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)Cl2] and an unidentified residue. Formation of [Zr(CpSi2Cp)Et2] is always accompanied by decomposition with the evolution of ethane to give [{Zr(CpSi2Cp)Et}2(μ-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(μ-CH2CH2)] were studied by X-ray diffraction methods. Density functional calculations on the model compound [{ZrCp2Me}2(μ-CH2CH2)] satisfactorily reproduce d C - C = 1.482, d1Zr - C = 2.327 Å, and d2Zr-C = 2.506 Å, the geometry found experimentally.

Intramolecular coordination of an alkene to a mixed dicyclopentadienyl benzyl zirconium cation studied by NMR spectroscopy

“…10 This description is consistent with the observed displacement of the CHN and SiCH 2 resonances to low field and of CH 2 N resonances to high field.…”

Synthesis and reactivity of new mixed dicyclopentadienyl Group 4 metal complexes with the doubly bridged bis(dimethylsilanediyl)-cyclopentadiene-(η5-cyclopentadienyl) ligand

“…However di-h 5 -cyclopentadienyl ligands singly bridged by various alkyl [2 -5] and silyl [6][7][8][9][10][11][12][13][14] groups are among the most frequently used systems to bridge dinuclear metal compounds. We have recently reported the use of the 1,1%-2,2%-(dimethylsilanediyl)dicyclopentadienyl ligand to synthesize ansadicyclopentadienyl and bridged homodinuclear monoand di-cyclopentadienyl complexes of the Group 4 and 6 metals [15][16][17][18][19][20]. This and related doubly silyl-bridged ligands have also been used [14,21] to isolate mononuclear and dinuclear Group 4 metal compounds.…”

β-Elimination and insertion of CNR in transient pentamethylcyclopentadienyl-imido-tantalum dialkyl complexes. X-ray structure of [TaCp*{N(2,6-Me2C6H3)}(CH2CH2)(PMe3)]

“…We have reported recently [4] novel aspects of the chemistry of doubly SiMe 2 -bridged dicyclopentadienylzirconium complexes with ihydrogen containing alkyl substituents and were interested in isolating similar group 5 metal compounds with the imido cyclopentadienyl fragment. The imido group is a useful stabilizing ligand for transition metal complexes in high oxidation state [5].…”