Long range interactions between nonconjugated π-systems - on the interaction of two CpCo-stabilized cyclobutadiene units

Oligoalkyne-Bridged (η4-Cyclobutadiene)(η5-cyclopentadienyl)cobalt Fragments − Syntheses and Properties

“…The positive charge of the resulting radical cation is delocalized over both Co atoms through the alkyne backbone, resulting in a higher second oxidation potential. The potential separation of 230 mV suggests that the electronic interaction is relatively weak, [38] therefore, we assign 15 to class II in the Robin and Day classification of mixed-valent compounds. [37] A different situation is observed for 18 and 21, where the first reversible oxidation potential is shifted towards a higher potential (by 50 mV) with respect to 14.…”

Synthesis and Properties of Donor/Acceptor-Substituted Metal-Capped Twofold-Sila-Bridged Cyclobutadieno Superphanes

“…[20] As reference we used the oxidation potentials of 1 and 32. [21] The latter species serves as a model for systems Table 1. Average distances [Å ] between the metal and the C(Cp) atoms (a) and the C(Cbd) atoms (b), respectively, the distances between the cyclobutadiene rings on the short-bridged side (c) and opposite (d) as well as the average angle (γ) [ Compound 32 shows only one oxidation potential ( Table 2) whereas for 1 two oxidation steps are observed.…”

“…The one at E 1 1/2 ϭ 656 mV was found to be reversible, whereas the second one at E 2p ox ϭ 1101 mV is irreversible. [9,21] The observed half-wave potentials for the reversible redox steps (E 1 1/2 and E 2 1/2 ) and the oxidation peak potentials for the irreversible steps (E 1p ox and E 2p ox ) of 10Ϫ18 are compiled in Table 2.…”

Toward a Square Grid Polymer: Electrochemistry of Tentacled Tetragonal Star Connectors, C4R4−Co−C5(HgY)5, on Mercury

“…The unsubstituted parent compound, CbCoCp, undergoes two irreversible oxidation processes at +0.79 and +1.14 V vs saturated calomel electrode (SCE), but its reduction has apparently not been examined. A derivative with four alkyl substituents on the Cb ring shows a reversible oxidation wave at +0.46 V vs SCE, and some more complicated structures with two Co centers have also been investigated, but once again, the reduction seems not to have been examined. A related cation, tetraphenylcyclobutadiene(benzene)cobalt(I), is reduced reversibly at −1.22 V vs SCE, then irreversibly at −1.75 V and finally again reversibly at −2.06 V, and the product is oxidized irreversibly at −0.23 V. A replacement of the four phenyl substituents with four methyl groups changes the reduction pattern; only one irreversible reduction at −1.92 V and one irreversible oxidation at −0.80 V are observed.…”