199684-38-3Relevant academic research and scientific papers
Binding and redox properties of iron(II) bonded to an oxo surface modeled by calix[4]arene
Esposito, Vittorio,Solari, Euro,Floriani, Carlo,Re, Nazzareno,Rizzoli, Corrado,Chiesi-Villa, Angiola
, p. 2604 - 2613 (2000)
The syntheses of the parent compounds [{p-Bu(t) - calix[4] - (O)2(OR)2}Fe - L] [R = Me, L = THF, 5; R = Bu(n), L = THF, 6; R = PhCH2, L = THF, 7; R = SiMe3, L = none, 8] have been performed by reacting the protonated form of the dialkylcalix[4]arene with [Fe2Mes4] [Mes = 2,4,6-Me3C6H2]. All of them undergo one-electron oxidative functionalization. By use of different oxidizing agents, the following iron(III) derivatives have been obtained: [{p-Bu(t) - calix[4] - (O)2(OR)2}Fe - X] [X = Cl, R = Me, 9; X = I, R = Me, 10] and [{p-Bu(t) - calix[4] - (O)2(OR)2}2Fe2(μ-X] [X = O, R = Me, 11; X = O, R = Bu(n), 12; X = S, R = Me, 13], 9 and 10 being particularly appropriate for a further functionalization of the metal. The last three display typical antiferromagnetic behavior [J = - 78.6 cm-1, 11; J = - 64.1 cm-1, 13]. In the case of 7 and 8, the reaction with O2 led to the dealkylation of one of the alkoxo groups, with the formation of a dimeric iron(III) derivative {[μ-p-Bu(t) - calix[4] - (O)3(OR)}2Fe2] [R = PhCH2, 14; R = SiMe3, 15] [J = - 9.8 cm-1]. The reaction of the parent compounds with Bu(t)NC and diazoalkanes led to the formation of [Fe = C] functionalities supported by a calix[4]arene oxo surface. The following compounds have been isolated and characterized: {[p-Bu(t) - calix[4] - (O)2(OR)2}Fe = CNBu(t)] [R = SiMe3, 16, v(CN) = 2175 cm-1], {[p-Bu(t) - calix[4] - (O)2(OR)2}Fe = CPh2] [R = Me, 17; R = PhCH2, 18; R = SiMe3, 19]. The three carbene complexes 17 - 19 display quite an unusual high-spin state, which is a consequence of the formation of a weak π interaction between the metal and the carbene carbon, as confirmed by the extended Huckel calculations. The carbene functionality has been removed from the iron center in the reaction with O2 and HCl. The proposed structures have been supported by X-ray analyses of complexes 8, 9, 12, 14, 16, 17, and 19.
