Regiospecific Coordination of Re3Clusters with the Sumanene-Type Hexagons on Endohedral Metallofullerenes and Higher Fullerenes That Provides an Efficient Separation Method

How Can the η1-Type Fullerene-Metal Bond Survive? A Systematic Survey of Reactions between Mono-EMFs and (M'Ln)2 Dimers

Recently, one η¹-coordinated complex of endohedral metallofullerene (EMF) Y@C_2v(9)-C₈₂[Re(CO)₅] has been synthesized and characterized with a highly efficient radical-coupling methodology by performing a photochemical reaction between Y@C_2v(9)-C₈₂ and [Re(CO)₅]₂ complexes. Theoretical investigations with the density functional theory reveal that this complex is stabilized by an ionic C-Re bond. The reactions of M@C_2v(9)-C₈₂ (M = Sc, Y, La) with [Re(CO)₅]₂ suggest that the reaction energies differ little because of similar single occupied molecular orbitals (SOMOs) of M@C_2v(9)-C₈₂. In the reactions of Y@C_2v(9)-C₈₂ with various transition-metal complexes [M'L_n]₂ (M' = Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir), the C-M' bonds with Mn, Tc, Re, Fe, Ru, and Os can stably exist, whereas those with Co, Rh, and Ir are unstable. Further analyses disclose that, in each element group, the stability of the C-M' bond is mainly determined by the bond energy of the M'-M' bond, which is related to the d_σ orbital of the M'L_n species. Moreover, the very-low-energy d_σ orbitals and large geometrical distortions of M'(CO)₄ (M' = Co, Rh, Ir) lead to poor stabilities of the C-M' (M' = Co, Rh, Ir) bonds. As comparison, the reactions of Y@C_s(6)-C₈₂ and La@C₇₂ have been investigated. The Y@C_s(6)-C₈₂ structure is more reactive toward the [M'L_n]₂ complexes than Y@C_2v(9)-C₈₂ thanks to a lower SOMO of Y@C_s(6)-C₈₂ than that of Y@C_2v(9)-C₈₂, which derives from position change of the Y atom in C_s(6)-C₈₂ during the reactions. However, the formation of [Y@C_s(6)-C₈₂]₂ suppresses the formation of several C-M' bonds. The reactivity of La@C₇₂ is weak due to a high LUMO+1 of C₇₂, which leads to a high SOMO of La@C₇₂. We believe that this theoretical study provides primary principles of radical-coupling reactions of EMFs and will be valuable for future research of organometallic complexes of fullerene.

Trapping Metallic Oxide Clusters inside Fullerene Cages

The sub-nanometer sized void inside a fullerene cage permits the accommodation of a single atom, atomic cluster, or even small molecule, resulting in the formation of endohedral fullerenes. Particularly, clusterfullerenes can be formed by encapsulating multiple metallic ions in most cases along with nonmetal ions (i.e., N^3-, C₂^2-, S^2-, O^2-) inside the fullerene cage. Such an association makes clusterfullerene more functional than empty fullerenes and conventional mono-metallofullerenes. To date, a variety of clusterfullerenes have been reported, including metal nitrides, carbides, oxides, sulfides, cyanides, and so on. Among them, oxide clusterfullerenes (OCFs) can contain variable oxide clusters (i.e., M₄O₂, M₄O₃, M₃O, and M₂O; M = Sc or other metal), yielding one of the most versatile families. Thus, OCFs may provide a more convenient platform for developing new functional molecules and for studying previously less-explored topics such as formation mechanisms of clusterfullerenes. In this Account, we review recent progress in the field of OCFs, including their synthesis, isolation, and structural and electrochemical studies as well as the preliminary exploration into their potential functions and applications. Thanks to the concrete crystallographic results of an OCF series, we can track the transition of endohedral cluster and fullerene cage. It is suggested that the configuration and internal dynamics of the oxide cluster are highly dependent on not only the cage size but also cage structure. On the other hand, based on the experimental observations, two competitive transformation pathways are established for the majority of OCFs, verifying the bottom-up or top-down formation mechanism. It is also found that the redox behaviors of OCFs are more or less comparable to their isoelectronic species with common cage structure and similar cluster geometry but varied greatly with the cluster variety (i.e., Sc₂O vs Sc₄O_2-3). The mechanism behind such phenomena has been discussed. In addition, the potential of Dy-based OCFs as single molecular magnets (SMMs) is presented theoretically. Nevertheless, experimental advance remains to be achieved.

W(CO)3(Ph2PC2H4PPh2)(η2-Sc3N@Ih-C80/Sc3N@D5h-C80): regioselective synthesis and crystallographic characterization of air-stable mononuclear complexes of endohedral fullerenes

Air-stable mononuclear coordination complexes of endohedral metallofullerenes have been regioselectively synthesized and crystallographically characterized for the first time.

The Solitary Isomer of C60 H18 Is Proven to Have a C3v Crown Shape: Crystal Structure Determination and Synthesis of Its Triruthenium Cluster Complex

Analytically pure C60 H18 is obtained by a Ru3 cluster complexation and decomplexation method. The crystal structure of C60 H18 consists of one flattened hemisphere, to which all 18 hydrogen atoms are symmetrically bonded, and one curved hemisphere akin to C60 . A benzenoid ring in the flattened hemisphere is isolated from the residual π systems by a belt composed of sp(3) -hybridized CH units. The average out-of-plane distances for carbon atoms attached to the benzenoid ring (0.14 Å) is substantially larger than that found in C60 F18 (0.06 Å). Several long C(sp(3) )C(sp(3) ) single bond lengths [1.61(3)-1.65(3) Å] are observed for C60 H18 . The reaction of [Ru3 (CO)12 ] and C60 H18 produces [Ru3 (CO)9 (μ3 -η(2) ,η(2) ,η(2) -C60 H18 )] (1), where the Ru3 triangle is regiospecifically linked to the hexagon opposite to the benzenoid ring. Compound 1 is the first transition metal complex of a polyhydrofullerene (fullerane). C60 H18 and 1 have been characterized by (1) H and (13) C NMR, UV/Vis, and mass spectroscopies. The HOMO-LUMO gap of C60 H18 is evaluated to be 1.51 V by cyclic voltammetry.

Beyond the Butterfly: Sc2C2@C(2v)(9)-C86, an Endohedral Fullerene Containing a Planar, Twisted Sc2C2 Unit with Remarkable Crystalline Order in an Unprecedented Carbon Cage

The synthesis, isolation, and characterization of a new endohedral fullerene, Sc2C88, is reported. Characterization by single crystal X-ray diffraction revealed that it is the carbide Sc2C2@C(2v)(9)-C86 with a planar, twisted Sc2C2 unit inside a previously unseen C(2v)(9)-C86 fullerene cage.

Synthesis and characterization of bis-triruthenium cluster derivatives of an all equatorial [60]fullerene tetramalonate

The parallel-[Ru₃(CO)₉]₂{μ₃-η²,η²,η²-C₆₀[C(COOC₂H₅)₂]₄} is the first complex where the two face-capping trinuclear metallic clusters coordinate to C₆₀ on opposite sites, in a parallel orientation.