C−D0 (D0 = π-donor, F) Cleavage in H2CCH(D0) by (Cp2ZrHCl)n: Mechanism, Agostic Fluorines, and a Carbene of Zr(IV)

Abstract
Consistent with the C−O cleavage behavior of vinyl ethers, vinyl fluoride reacts with Cp2ZrHCl to give Cp2ZrFCl and C2H4 as primary products. DFT (B3PW91) calculations show this reaction to be highly exoenergetic (−55 kcal/mol), and reveal a σ-bond metathesis mechanism to be unfavorable compared to a Zr−H addition across the CC bond, with regiochemistry placing F on Cβ of the resulting fluoroethyl ligand. β-F elimination (onto Zr) then completes the reaction. There is no η2-olefin intermediate on the reaction path. DFT calculations seeking the energy and structure of the two carbenes Cp2ZrHCl[CF(CH3)] and Cp2ZrFCl[CH(CH3)] are also described.

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