141886-52-4Relevant academic research and scientific papers
Polyalkoxybenzylation of [FeCp(arene)]+ complexes and polyfunctionalization of the tentacles with iron sandwich redox centers
Fillaut, Jean-Luc,Astruc, Didier
, p. 945 - 957 (2008/10/08)
The reaction of [FeIICp(C6Me6)]+PF6 -, 1, (Cp = η5-C5H5) wih t-BuOK and para-alkoxybenzylbromides of various chain lengths in DME for 1 day at 40°C reproducibly gives the hexa[p-alkoxybenzylation] complexes [FeIICp{C6(CH2CH2PhOR) 6}]+PF6-, 3, [R = Me (a), Et (b), C7H15 (c), C6H12OCH3 (d), or C11H23 (e)] resulting from single branching in yields around 60%. Double branching is achieved upon octamethoxybenzylation of [FeCp(durene)]+PF6- 6, using KOH and p-MeOPhCH2Br in DME which gives [FeCp(1,2,4,5-{CH(CH2PhOMe)2}4C 6H2)]+PF6-, 7, and triple branching is achieved upon trimethoxybenzylation of [FeCp(toluene)]+PF6-, 4, which gives [FeCp{C6H5C(CH2PhOMe)3}] +PF6-, 5, under analogous conditions. Decomplexation of the iron sandwich derivatives 3 proceeds in yields around 90% by photolysis with visible light in MeCN in the presence of 1 equiv. of PPh3 to give the ether-soluble free aromatics 10a-d and [FeIIICp(NCMe)2(PPh3)]+PF 6-. Reaction of the hexa[p-methoxybenzyl] derivatives 3a and 10a with BBr3 in CH2Cl2 gives nearly quantitative yields of the hexaphenols 11 and 12. The latter are alkylated by reaction with BrCH2CN and K2CO3 in THF to give the hexanitriles 13 and 14. Efficient esterification of the hexaphenols requires prior formation of the hexathallium phenates, which precipitate upon reaction of the hexaphenols with TlOEt in THF. The hexathallium phenate 12 reacts with organic acyl chlorides in THF to give high yields of the hexaesters 17. The hexaphenols 11 and 12 react in this way with Fc COCl (Fc = ferrocenyl), giving the heptametallic hexaester [FeCp{C6(CH2CH2PhOCOFc)6}) +PF6-, 15, and the hexaferrocene hexaester C6(CH2CH2PhOCOFc)6, 16, respectively. The organic hexaphenol 12 undergoes nucleophilic substitution of the chloride by phenate in [FeCp(p-ClPhMe)]+PF6- to give the hexanuclear hexacationic complex C6[CH2CH2PhO(-PhFe+Cp)] 6(PF6-)6, 18, in 65% yield. The cyclic voltammogram (CV) of the heptanuclear complex 15, at - 35°C in DMF, shows two reversible waves with an intensity ratio of 1:6.3 ± 0.3, indicating the presence of six ferocene units per [FeCp(arene)]+ in the molecule; similarly, the CV of the hexametallic complexes 16 and 18 show electrochemically reversible waves; the oneness of the hexaelectron wave in 15, 16 and 18 (ΔEp ≤ 80 mV) shows the independence of the six redox centers located at the periphery of these molecules. CNRS-Gauthier-Villars.
