Dialkyl and Methyl-Alkyl Zirconocenes: Synthesis and Characterization of Zirconocene-Alkyls That Model the Polymeryl Chain in Alkene Polymerizations

• Zirconocene precatalysts with sterically bulky alkyl groups were designed as model systems for the propagating species in zirconocene-catalyzed alkene polymerization. Specialty alkyllithium reagents Li(CH2CEt3) and Li(CH2CMe2CH2Ph) were prepared and utilized in the synthesis of dialkyl and methyl-alkyl zirconocenes of the form CpCp*ZrR2, Cp2Zr(CH3)(R), and CpCp*Zr(CH3)(R) (Cp = (5-C5H5); Cp* = (5-C5Me5); R = CH2CMe3, CH2SiMe3, CH2CEt3, CH2CMe2CH2Ph). These new zirconocene alkyls were isolated and fully characterized by NMR spectroscopy and in some cases by X-ray diffraction. The molecular structures determined display the bent-sandwich coordination mode common for zirconocenes. The steric influence of the alkyl group on the observed structural parameters is reflected in slightly expanded C-Zr-C or C-Zr-Cl angles in the equatorial plane and long zirconium-alkyl bond distances.

Subject headings

NATURVETENSKAP  -- Kemi -- Organisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Organic Chemistry (hsv//eng)

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art (subject category)

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