Vicinal fluorine–fluorine coupling constants in perfluoropropyl groups

[(MeCN)3Co(C2F5)3]: A Versatile Precursor to Cobalt(III) Perfluoroethyl Complexes

“…The silver(I) salts serve the dual role of forming a stable silverbased perfluoroethyl transfer reagent as well as a one electron oxidant to oxidize Co(II) to Co(III). 13 Me 3 Si-F was detected as a byproduct by 19 F NMR spectroscopy, and a silver mirror on the reaction vessel could be observed upon completion of the reaction. The acetonitrile complex 1 is an air-stable solid that, once isolated, shows air stability even in solution (see below).…”

“…It is known, but rarely discussed, that NMR resonances of isolated perfluoroethyl groups commonly appear as two singlets and exhibit little to no vicinal coupling . The absence of or low values for 3 J FF for perfluoroalkyl groups has been suggested to arise in part from rotational averaging of coupling constants of opposite sign between the vicinal CF 2 and CF 3 groups. − Complex 5 is an interesting case study because the meridional geometry imposed by the terpyridine ligands affords two different types of isolated perfluoroethyl groups in a 2:1 ratio with the ability of the distinct perfluoroethyl groups to exhibit long-range couplings to one another despite displaying no vicinal couplings within an individual perfluoroethyl group. Thus, in complex 5 , the CF 3 resonance of the axial perfluoroethyl groups appears as a triplet since it couples to the sole CF 2 group of the other perfluoroethyl situated trans to a nitrogen.…”

Solvated Nickel Complexes as Stoichiometric and Catalytic Perfluoroalkylation Agents**

“…The CF 3 resonance that is trans to the coordinated acetonitrile appears as a quintet from the 5 J FF coupling of the other two CF 2 groups, while the resonance for the CF 3 groups that are cis to the acetonitrile appear as a triplet. The absence of 3 J FF coupling is common for perfluoroalkyl groups and is suggested to arise from the rotational averaging of coupling constants of opposite sign between the vicinal CF 2 and CF 3 groups [30–33] …”

“…Thea bsence of 3 J FF coupling is common for perfluoroalkyl groups and is suggested to arise from the rotational averaging of coupling constants of opposite sign between the vicinal CF 2 and CF 3 groups. [30][31][32][33] Thee lectrochemical properties of the newly prepared anionic complex 5 were evaluated by cyclic voltammetry (Figure 1). Theoxidation of 5 is irreversible and occurs at an onset potential of + 0.21 Vv s. the ferrocene/ferrocenium couple.Peak potentials for 5 appear at + 0.60 Vand + 1.26 V, which are slightly more positive than peaks observed for the trifluoromethyl derivative 2.…”

Solvated Nickel Complexes as Stoichiometric and Catalytic Perfluoroalkylation Agents

“…The absence of 3 JFF coupling is common for perfluoroalkyl groups and is suggested to arise from the rotational averaging of coupling constants of opposite sign between the vicinal CF2 and CF3 groups. [30][31][32][33] The electrochemical properties of the newly prepared anionic complex 5 were evaluated by cyclic voltammetry (Figure 2). The oxidation of 5 is irreversible and occurs at an onset potential of +0.21 V vs the ferrocene/ferrocenium couple.…”