A series of (alkoxymethyl)zirconocene chlorides (1, Cp2Zr(Cl)CH2OR, Cp = n5-C5H5) has been prepared by treatment of Cp2ZrCl2 with (alkoxymethyl)lithium reagents. Compound 1c, Cp2Zr(Cl)CH2OCH2C6H5, crystallizes in the orthorhombic space group Pbca, with a = 15.417 (9) A, b = 18.249 (9) A, c = 11.746 (8) A, and Z = 8. The X-ray crystal structure shows that the alkoxymethyl ligand is n2, with a significant Zr-O interaction. Compounds 1 with R= benzyl or substituted benzyl undergo a Wittig rearrangement when heated to give products 3 (Cp2Zr(Cl)OCH2R). The activation parameters that were determined for the transformation, the effects of substituents on the rate of the reaction, the identity of the reaction’s side products, and the retention of configuration at the benzylic carbon are all consistent with the formation of a short-lived radical pair intermediate.
“Synthesis of (alkoxymethyl)zirconocene chlorides: stereochemistry of carbon-carbon bond formation in a zirconocene-Wittig rearrangement”, Organometallics, 1989, 8(7), 1593-1598.