To understand the selectivity of the stoichiometric C-F bond-cleavage reaction, we performed a series of DFT calculations at the M06/6-311++G(d,p)//B3LYP-D3/6-31g(d) level in which IiPr (L) was employed as a truncated model for ICy in order to reduce computational costs (Figure ). The results revealed that the reaction of difluoroenolate A and Ni2(IiPr)4(cod) (B), which is generated from Ni(cod)2 and L, to form the η 2complex C is a thermally favored process. The subsequent coordination of LiCl(thf)2 to give complex D is also thermally favored. The transition state TS1 (Figure , left) for fluoride elimination assisted by the Li cation was calculated to produce complex E with an energetic barrier of 28.7 kcal/mol. The abstraction of chloride by the cationic nickel center furnishes the oxidative-addition product F. The oxidative addition of the C-F bond without the support of a lithium salt via TS2 (Figure , right) was calculated to require 35.5 kcal/mol, which is significantly higher than the barrier for TS1. These calculations are in agreement with the experimentally observed requirement for a lithium salt for the oxidative addition to proceed smoothly. We propose that the critical factor determining the E/Z selectivity of the oxidative addition is the different degrees of steric congestion around the two fluorine atoms. We prepared topographic steric maps using SambVca 2.1 to visualize the steric environment around the fluorine atoms located cis and trans to the siloxy group, which are labeled as F 1 and F 2 , respectively (Figure ). The topographic steric map with F 1 -Ni oriented along the z-axis indicated that F 1 is shielded by three methyl groups, two of which are attached to the TMS group and one of which belongs to the isopropyl group of L. In contrast, F 2 is located in a plane surrounded by a phenyl group and two methyl groups of TMS and L. The %Vbur values for F 1 and F 2 were 28.4 and 19.8, respectively, which supports the notion of significantly different steric hindrance around the fluorine atoms. Hence, it seems feasible to assume that the lithium cation coordinates exclusively to the less-congested F 2 , which results in a selective cleavage of that C-F bond that produces the E isomer. b Yields were determined via F NMR analysis of the crude reaction mixture using trifluoromethyl cyclohexane as an internal standard; n.d. = not detected. c Using isolated ZnPh2 (purified by sublimation).