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Two Regioisomers of Endohedral Pyrrolidinodimetallofullerenes M 2 @ I h ‐C 80 (CH 2 ) 2 NTrt (M=La, Ce; Trt=trityl): Control of Metal Atom Positions by Addition Positions
Author(s) -
Yamada Michio,
Okamura Mayuko,
Sato Satoru,
Someya Chika I.,
Mizorogi Naomi,
Tsuchiya Takahiro,
Akasaka Takeshi,
Kato Tatsuhisa,
Nagase Shigeru
Publication year - 2009
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/chem.200900993
Subject(s) - paramagnetism , adduct , pyrrolidine , chemistry , cerium , metal , crystallography , endohedral fullerene , structural isomer , ring (chemistry) , fullerene , stereochemistry , inorganic chemistry , physics , organic chemistry , quantum mechanics
Abstract The two regioisomers of endohedral pyrrolidinodimetallofullerenes M 2 @ I h ‐C 80 (CH 2 ) 2 NTrt (M=La, Ce; Trt=trityl) were synthesized, isolated, and characterized. X‐ray crystallographic analyses of [6,6]‐La 2 @ I h ‐C 80 (CH 2 ) 2 NTrt and [6,6]‐Ce 2 @ I h ‐C 80 (CH 2 ) 2 NTrt revealed that the encapsulated metal atoms are located at the slantwise positions on the mirror plane that parallels the pyrrolidine ring. Paramagnetic NMR analyses of [6,6]‐ and [5,6]‐Ce 2 @ I h ‐C 80 (CH 2 ) 2 NTrt were also carried out to clarify the metal positions. As for the [6,6]‐adduct, the metal positions obtained by paramagnetic NMR analysis agree well with the X‐ray structure. In contrast, paramagnetic NMR analysis of the [5,6]‐adduct showed that the two Ce atoms are collinear with the pyrrolidine ring. We also compared the observed paramagnetic effects of the pyrrolidinodimetallofullerenes with those of other cerium‐encapsulating fullerene derivatives such as bis‐silylated Ce 2 @ I h ‐C 80 and a carbene adduct of Ce 2 @ I h ‐C 80 . We found that the metal positions can be explained by the electrostatic potential maps of the corresponding [6,6]‐ and [5,6]‐adducts of [ I h ‐C 80 (CH 2 ) 2 NTrt] 6− . These findings clearly show that metal positions inside fullerene cages can be controlled by means of the addition positions of the addends. In addition, the radical anions of the pyrrolidinodimetallofullerenes were prepared by bulk controlled‐potential electrolysis and characterized by X‐band EPR spectral study.