Co(I)-Mediated Removal of Addends on the C₆₀ Cage and Formation of the Monovalent Cobalt Complex CpCo(CO)(η²-C₆₀)

Abstract

The removal of addends on the fullerene C cage plays an important role in the final stage for synthesizing endohedral fullerenes by the molecular surgery method. We developed a cobalt-mediated reaction to regenerate C from N-substituted C derivatives (aziridinofullerene and azafulleroid). In these reactions, we found the formation of a green monovalent-cobalt complex of C, and its structure was unambiguously determined by X-ray analysis. The characteristic electronic structure of this cobalt complex was studied by IR and UV-vis absorption spectroscopy and electrochemical analyses.

Palladium-Catalyzed Cyclization: Regioselectivity and Structure of Arene-Fused C60 Derivatives

“…Recently, transition-metal-mediated functionalization of C 60 has received growing attention because of the potential feasibility of high conversion and yield. − For example, the successful syntheses of chiral C 60 derivatives using asymmetric catalysts such as Cu­(II) or Ag­(I) salt have been reported by Martin and co-workers. , In most cases, however, a stoichiometric amount of transition metal reagents is required. ,,,− Most recently, several methods for structural modification of C 60 using rhodium- or palladium-catalyst have been developed. , In particular, the research groups of Wang and Itami have been independently made a remarkable contribution to this research field. − As the simplest arene-fused C 60 derivatives, there is a report on the synthesis of naphthalene-fused C 60 derivative 1 containing one pentagonal ring . According to this report, 1 was prepared from C 60 and 1,8-diiodonaphthalene under the pyrolytic conditions and the yield lies in the range of 1–14%.…”

Synthesis and Oligomerization of CpM(CO)2

“…The synthesized complexes, CpM­(CO) 2 , can be stored under an inert atmosphere of N 2 at 4 °C over two years despite forming precipitates in a tiny amount during storage. The supernatant, however, worked well for the common ligand exchange reactions with olefins and did not show significant change in 1 H NMR and IR spectra. Upon seeing the precipitates, we noticed the presence of single crystals, revealing their structures as oligomers by X-ray crystallography (vide infra).…”

π-Backbonding on Group 9 Metal Complexes Bearing an η2-(H2O@C60) Ligand

“…By the reaction of C 60 with 2 equiv of CpCo(CO) 2 in o-dichlorobenzene (ODCB) at 180 °C, the desired complex CpCo(CO)(η 2 -C 60 ) (1 Co ) was obtained in 47% isolated yield (Table 1, entry 1), whose structure was previously characterized by single-crystal X-ray diffraction analysis. 13 By replacing CpCo(CO) 2 with CpRh(CO) 2 , the corresponding complex CpRh(CO)(η 2 -C 60 ) (1 Rh ) was afforded in 35% yield, which was improved to 43% by extending the reaction time to 2 h (entries 2 and 3). Under the similar conditions, CpIr(CO)(η 2 -C 60 ) (1 Ir ) was obtained albeit in 17% yield (entry 4).…”

“…Different from most group 10 metal complexes of C 60 , 9−11 1 M was stable during chromatographic purification over silica gel, whereas they gradually liberate the η 2 -C 60 ligand in a dilute CS 2 solution (<1.5 mM) presumably caused by the competitive coordination of CS 2 to the metal center (ca. 5% decomposition per a day estimated by 13 C NMR). Interestingly, 1 Rh and 1 Ir exhibited high photostability without considerable decomposition by irradiation at 365 nm over 12 h, while 1 Co was quantitatively converted into C 60 within 1 h. 13 This is again due to larger bond dissociation energies for higher-row elements.…”