Mechanism of the Reaction of Vinyl Chloride with (α-diimine)PdMe+ Species

The reaction of vinyl chloride (VC) with (α-diimine)PdMe+ species yields (α-diimine)PdCl(propene)+. Isotope labeling experiments using the deuterium-labeled vinyl chlorides 1-VC-d1 and Z-VC-d1 combined with DFT computations establish that this reaction proceeds by 2,1-insertion of VC to produce β-H agostic (α-diimine)Pd(CHClCH2Me)+, chain-walking isomerization to generate β-Cl dative (α-diimine)Pd(CHMeCH2Cl)+, and syn β-Cl elimination. The labeling experiments rule out mechanisms involving initial 1,2-insertion or C−Cl oxidative addition. The computational results and the observation of small amounts of propene-d2 argue against mechanisms involving 2,1-insertion followed by α-Cl elimination and a 1,2 H-shift.