Origin of enantioselectivity M Pd

The enantioselectivity-determining alkene insertion step involves a four-membered cyclic transition state, which adopts a square-planar geometry. When a chiral bidentate ligand, such as PyOx, is employed, there are four possible isomeric alkene insertion transition states (Table 2.2). 

Source Reprinted with permission from Holder, J. C. et al., /. Am. Chem. Soc., 135, 14996-15007. Copyright 2013 American Chemical Society. 

---