Ionic Sn2 type mechanism

Activation of Substrates with Polar Single Bonds 

Though the stereochemistry for oxidative addition of allylic halide had been rather ambiguous until 1990s, it was found to vary depending on the reaction conditions. Cyclic allylic carboxylates were mainly employed to obtain the stereochemical information for the oxidative addition of allylic electrophiles in general (cf. Section 3.3). As shown in Eq. 3.3 the oxidative addition of the trans allylic chloride to Pd2(dba)3 in a polar solvent such as acetonitrile or DMSO dominantly gives the cis product (trans/cis = 3/97 in DMSO), suggesting conventional Sn2  

The prior r -coordination is also proposed for oxidative addition of phenyl-propargyl halides to zero-valent platinum complex Pt(PPh3)4, where Pt(PPh3)2 and Pt(PPh3)3 are active species for the oxidative addition. Kinetic study reveals slow formation of Pt(r/ -PhC=CCH2X)(PPh3) n = 2, 3), from which 

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