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

Consistent with the C-O cleavage behavior of vinyl ethers, vinyl fluoride reacts with Cp(2)ZrHCl to give Cp(2)ZrFCl and C(2)H(4) as primary products. DFT (B3PW91) calculations show this reaction to be highly exoenergetic (-55 kcal/mol), and reveal a sigma-bond metathesis mechanism to be unfavorable compared to a Zr-H addition across the C=C bond, with regiochemistry placing F on C(beta) of the resulting fluoroethyl ligand. beta-F elimination (onto Zr) then completes the reaction. There is no eta(2)-olefin intermediate on the reaction path. DFT calculations seeking the energy and structure of the two carbenes Cp(2)ZrHCl[CF(CH(3))] and Cp(2)ZrFCl[CH(CH(3))] are also described.