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{FeCp} + ‐Induced Hexafunctionalization of Hexamethylbenzene with Dendrons for the Direct Synthesis of Redox‐Active Iron‐Centered Metallodendrimers
Author(s) -
Nlate Sylvain,
Nieto Yolanda,
Blais JeanClaude,
Ruiz Jaime,
Astruc Didier
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20020104)8:1<171::aid-chem171>3.0.co;2-4
Subject(s) - dendrimer , hexamethylbenzene , chemistry , redox , ferrocene , cyclic voltammetry , alkyl , ligand (biochemistry) , electron transfer , crystallography , photochemistry , polymer chemistry , inorganic chemistry , electrochemistry , organic chemistry , benzene , biochemistry , receptor , electrode
Abstract Phenol tri‐ and nonaallyl dendrons ( 3 and 7 , respectively) were functionalized at the focal position to give the new triallyl dendrons 4 and 6 and the nonaallyl dendrons 11 and 13 that contain a iodoalkyl or a bromobenzyl termini. All these dendrons were used for the {FeCp} + ‐induced hexafunctionalization of hexamethylbenzene in [FeCp( η 6 ‐C 6 Me 6 )][PF 6 ] ( 1 ) under mild conditions in the presence of KOH. These reactions directly yielded the 18‐allyl and 54‐allyl dendrimers 9, 10 , and 14 with a [FeCp( η 6 ‐arene)] + unit located at the dendrimer core. Cyclic voltammetry studies were recorded in THF and DMF with these metallodendrimers and compared with those of analogous dendrimers or complexes of smaller size that contain a [FeCp( η 6 ‐arene)] + unit at the core. The decreased rate of heterogeneous electron transfer when the dendritic size increases first disclosed by Diederich and Gross is confirmed. The variation of the redox potential of the Fe II/I redox system with increasing dendritic size is negligible even in a solvent of high dielectric constant such as DMF. This trend is attributed to fact that the involved “redox” orbital is buried on the metal center, well protected by the shell of alkyl chains (electron‐reservoir nature), unlike in ferrocene. The chemical irreversibility increases in THF as the dendrimer size increases, due to more facile ligand substitution with THF at the 19‐electron level when the chain bulk increases.