C2F4 Coupling constants have been evaluated at EOM-CCSD/(qzp,qz2p) in binary complexes With electron donors X (X = HLi, Cl-, CN-) and with the electron acceptor FH, and in tertiary complexes FH:C2F4:X in which X and FH are located on opposite faces of the C2F4 pi Cloud. The electron donors X and the electron acceptor FH have opposite effects on (1)J(C-C), (1)J/(C-F), (2)J(C-F), and (3)J(F-F) in binary complexes. Effects of X and FH on a particular Coupling constant in a ternary complex are additive if the change in the coupling constant in this complex relative to C2F4 is within 1 Hz of the SLIM of the changes in the corresponding binary complexes. This is the case for (1)J(C-F). Both positive and negative nonadditivities are computed for the remaining Coupling constants. Although the values Of Most Coupling constants lie between the Values for FH:C2F4 and C2F4:X, that is not the case for (2)J/(C-F), and the effect of FH is enhanced by the presence of X. Moreover, values of, 3./(F-F) trans and cis for FH:C2F4:X when X is Cl- or CN- bonded through C are within I Hz of the values For the corresponding binary complex C2F4:X Significant differences can be Found between the relative contributions of the PSO, FC, and SD terms to total J and to the nonadditivities of J in ternary complexes FH:C2F4:X.