Synthesis of Silylene-Bridged Endohedral Metallofullerene Lu₃N@I_h-C₈₀

Abstract

Functionalization of endohedral metallofullerenes has been shown to differ depending on photochemical or thermal pathways. We report that Lu(3)N@I(h)-C(80) reacts with thermally generated bis(2,6-diethylphenyl)silylene with high selectivity and forms monosilylated derivative 1b. Unexpectedly, 1b undergoes photochemical conversion to afford isomer 1a under ambient light. These adducts were characterized using NMR, visible-near-IR spectroscopy, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Single-crystal X-ray structure determination of 1a reveals a rare example of an open 1,2-adduct at the [5,6]-ring junction of the I(h)-C(80) cage. The electrochemical study reveals that the redox potentials of 1a and 1b are shifted cathodically compared to those of pristine Lu(3)N@I(h)-C(80) and that monosilylation is effective to fine-tune the electronic properties of endohedral metallofullerenes as well as empty fullerenes. Density functional theory calculations were also performed, which provide a theoretical basis for the structures and the behavior of the encapsulated Lu(3)N cluster.

[5,6]‐Open Methanofullerene Derivatives of Ih‐C80

“…[12] Cyclopropanation-type reactions have been used to modify EMFs to yield methanofullerenes [13] and recently, azafulleroids [14] and silylene-bridged derivatives. [15] There are two distinct addition sites available on the I h isomer of C 80 fullerenes: C À C bonds at [6,6] ring junctions (pyrene-type sites) and CÀC bonds at [5,6] ring junctions (corannulenetype sites). In 2005, Poblet and co-workers [16] reported that the corannulene [5,6] bonds closest to the Sc atoms have the highest strain of all bonds in the I h -C 80 cage.…”

“…[13, 19,20] Although nitrogen [14] and silicon bridges [15] at [5,6] bonds have been reported, the corresponding methano adducts have remained elusive.…”

Emergence of Highly Elaborated π-Space and Extending Its Functionality Based on Nanocarbons: New Vistas in the Fullerene World

“…In fact, thermal reaction of Lu 3 N@I h (7)-C 80 with the precursor yielded two isomers of the silylene adducts, of which a major isomer was isolated and the structure solved by single-crystal XRD (Figure 19). 131 The other was rather unstable. It was transformed slowly into the major isomer under ambient light.…”

Thermal Reactions of Fullerenes with Cyclic Organosilicon and Organogermanium Compounds: Silylation and Germylation of C60 and C70

“…Chemical functionalization of fullerenes has been attracting much attention from both mechanistic and synthetic viewpoints . An introduction of heteroatoms such as electropositive silicon has been known as an effective method to modify the electronic characteristics of empty fullerenes and endohedral metallofullerenes . The facile silylation reactions of fullerenes have been described using reactive silicon compounds such as silylenes , disiliranes , and silyl radicals .…”

“…Therefore, alternative procedures for silylation of fullerenes are desirable for the development of various silylated fullerene‐based materials. Recently, thermal addition reactions of endohedral metallofullerenes with disiliranes, digermiranes , siliranes , and silylenes have been demonstrated to afford the corresponding silylated derivatives. In addition, thermal reactions of C 60 with siliranes have been reported to afford carbosilylated and monosilylated products .…”