Notably, the redox-active ester protocol requires BiOx as ligand whereas the trifluoromethyl alkene protocol requires L1, and a recent study from Diao 30 illustrates that bipyridyl complex of nickel are much more easily reduced than are the corresponding BiOx complexes, which provides a potential rationale for the differing behavior of these catalytic systems. Additionally, we attributed reactivity of 1a with redox-active esters to be derived from intermediates similar to VII in our recent report of aldehyde / redox-active ester couplings. 21c The product 11 from the current study, however, is unusual and informative in several respects. First, the putative ring-opened organometallic intermediate VII undergoes chain-walking 28g,j,32 through VIII to intermediate IX prior to capture by 2j, ultimately forming the branched isomer of product 11. In contrast, our recent report of aldehyde couplings with redox-active esters led exclusively to ring-opened products but without evidence for chain walking. 21c We attribute this difference to be the result of the changes in ligand structure between redox-active ester couplings (BiOx) and trifluoromethyl alkene couplings (L1). While we originally envisioned that VII was likely derived from VI, the recent evidence from Weix illustrating the direct formation of VII from 1q is detailed and convincing. Formation of a ketyl radical through homolysis of VI would not afford the rearranged constitution of 11 unless recombination of the radical with nickel again leads to intermediate VII. Formation of the Z-isomer of the enol silane of 11 is consistent with the formation of cyclic intermediates such as VII and IX where the alkene is constrained within a ring. Other rearrangements involving Ni(0) catalyzed cyclopropyl ketone rearrangements have been described, but only under much higher temperature conditions with different ligand types. Those studies documenting the formation of intermediates such as VII in the absence of silyl electrophiles showed that a,b-unsaturated carbonyl intermediates were produced through this pathway. While this potentially suggests that crotonaldehyde produced from intermediates analogous to VII could be an intermediate in the formation of 1q, when crotonaldehyde was used in place of aldehyde 1q, only trace quantities of 11 were observed. On this basis, we favor the pathway depicted in Scheme 3B as the operative mechanism for the production of 11. Treatment of 1q and 2j to conditions using CrCl 3 described by Wang 29 afforded no product 11, providing further evidence that the Ni and Cr procedures fundamentally differ in mechanism. With the insights from the behavior of substrate 1q, the involvement of organometallic intermediates such as I, II, and IV seem most likely in the reductive couplings described in Tables and rather than ketyl-derived additions directly to the trifluoromethyl alkene.