Although most of the MC-type metallofullerenes (EMFs) tend to form carbide cluster EMFs, we report herein that Lu-containing EMFs LuC (2n = 82, 84, 86) are actually dimetallofullerenes (di-EMFs), namely, Lu@C(6)-C, Lu@C(8)-C, Lu@D(23)-C, and Lu@C(9)-C. Unambiguous X-ray results demonstrate the formation of a Lu-Lu single bond between two lutetium ions which transfers four electrons in total to the fullerene cages, thus resulting in a formal divalent state for each Lu ion. Population analysis indicates that each Lu atom formally donates a 5d electron and a 6s electron to the cage with the remaining 6s electron shared with the other Lu atom to form a Lu-Lu single bond so that only four electrons are transferred to the fullerene cages with the formal divalent valence for each lutetium ion. Accordingly, we confirmed both experimentally and theoretically that the dominating formation of di-EMFs is thermodynamically very favorable for LuC isomers.

A series of iridium tetrahydride complexes [Ir(H)(4)(PSiP-R)] bearing a tridentate pincer-type bis(phosphino)silyl ligand ([{2-(R(2)P)C(6)H(4)}(2)MeSi](-), PSiP-R, R=Cy, iPr, or tBu) were synthesized by the reduction of [IrCl(H)(PSiP-R)] with Me(4)N·BH(4) under argon. The same reaction under a nitrogen atmosphere afforded a rare example of thermally stable iridium(III)-dinitrogen complexes, [Ir(H)(2)(N(2))(PSiP-R)]. Two isomeric dinitrogen complexes were produced, in which the PSiP ligand coordinated to the iridium center in meridional and facial orientations, respectively. Attempted substitution of the dinitrogen ligand in [Ir(H)(2)(N(2))(PSiP-Cy)] with PMe(3) required heating at 150 °C to give the expected [Ir(H)(2)(PMe(3))(PSiP-Cy)] and a trigonal bipyramidal iridium(I)-dinitrogen complex, [Ir(N(2))(PMe(3))(PSiP-Cy)]. The reaction of [Ir(H)(4)(PSiP-Cy)] with three equivalents of 2-norbornene (nbe) in benzene afforded [Ir(I)(nbe)(PSiP-Cy)] in a high yield, while a similar reaction of [Ir(H)(4)(PSiP-R)] with an excess of 3,3-dimethylbutene (tbe) in benzene gave the C-H bond activation product, [Ir(III)(H)(Ph)(PSiP-R)], in high yield. The oxidative addition of benzene is reversible; heating [Ir(III)(H)(Ph)(PSiP-Cy)] in the presence of PPh(3) in benzene resulted in reductive elimination of benzene, coordination of PPh(3), and activation of the C-H bond of one aromatic ring in PPh(3). [Ir(III)(H)(Ph)(PSiP-R)] catalyzed a direct borylation reaction of the benzene C-H bond with bis(pinacolato)diboron. Molecular structures of most of the new complexes in this study were determined by a single-crystal X-ray analysis.

The long-sought Y–Y bonding is experimentally observed in organometallic complexes for the first time by encapsulation inside the hollow cavity of C3v(8)-C82 and Cs(6)-C82 fullerene cages.

A series of giant metallofullerenes YC (2n = 92-130) have been successfully obtained through the treatment of the fraction enriched by 1,2-dichlorobenzene with SnCl. Subsequent chromatographic separation gives a pure sample with a composition of YC. Crystallographic results reveal that this endohedral takes the carbide form, namely YC@C(1660)-C, representing as the largest metallofullerene that has been characterized by crystallography to date. Despite the disorder of the metal cluster, the major YC adopts a previously predicted linear configuration, indicating that the compression of the internal cluster by the cage is almost negligible in this giant cage. Electrochemical studies suggest that YC@C(1660)-C is a good electron donor instead of an electron acceptor.