Transition Metal/Lanthanide-Nitrogen Double Bonds Co-stabilized in a Carbon Cage

Metal−nitrogen double bonds have been commonly reported for conventional metal complexes,but the coexistence of both transition metal−nitrogen and lanthanide−nitrogen double bonds bridged by nitrogen within one compound has never been reported.Herein,by encapsulating a ternary transition metallanthanide heteronuclear dimetallic nitride into a C_(84) fullerene cage,transition metal−nitrogen and lanthanide-nitrogen double bonds are costabilized simultaneously within the as-formed clusterfullerene TiCeN@C_(1)(12)-C_(84),which is a representative heteronuclear dimetallic nitride clusterfullerene.Its molecular structure was unambiguously determined by single-crystal X-ray diffraction,revealing a slightly bentμ2-bridged nitride cluster with short Ti−N(1.761Å)and Ce−N(2.109Å)bond lengths,which are comparable to the corresponding Ti=N and Ce=N double bonds of reported metal complexes and consistent with the theoretically predicted values,confirming their coexistence within TiCeN@C_(1)(12)-C_(84).Density functional theory(DFT)calculations unveil three-center two-electron(3c-2e)bonds delocalized over the entire TiCeN cluster,which are responsible for costabilization of Ti�N and Ce�N double bonds.An electronic configuration of Ti4+Ce^(3+)N^(3−)@C_(84)^(4−)is proposed featuring an intramolecular four-electron transfer,drastically different from the analogous actinide dimetallic nitride clusterfullerene(U_(2))^(9+)N^(3−)@C_(80)^(6−)and trimetallic nitride clusterfullerene(Sc_(2))^(6+)Ti^(3+)^(N3−)@C_(80)^(6−),indicating the peculiarity of 4-fold negatively charged fullerene cage in stabilizing the heteronuclear dimetallic nitride cluster.

ScY@C_(3v)(8)-C_(82):Metal-Metalσ^(2)Bond in Mixed Rare-Earth Di-metallofullerenes

Comprehensive Summary The experimental investigation of rare-earth metal-metal bonds remains a challenge in the study of chemical bonds.Herein,we report the synthesis and characterization of a novel heteronuclear di-metallofullerene,ScY@C_(3v)(8)-C_(82),which contains a mixed rare-earth metal-metal bond.ScY@C_(3v)(8)-C_(82)was successfully synthesized by arc-discharging method and characterized by mass spectrometry,UV-vis-NIR spectroscopy and single-crystal X-ray diffraction crystallography,which unambiguously determined its molecular structure.Theoretical calculations were also performed to study the optimized positions of Sc-Y metallic dimer and the electronic configuration.The combined experimental and theoretical results confirmed that both Sc and Y atoms transfer two electrons to the C_(3v)(8)-C_(82)cage,i.e.,(ScY)4+@(C_(3v)(8)-C_(82))4-.In particular,a covalent Sc-Yσ2 bond,which has never been reported before,is proven to be formed inside C_(3v)(8)-C_(82)fullerene cage.This work presents a novel di-metallofullerene containing mixed rare-earth metal-metal bond and expands the understanding of metal-metal bonding of rare earth elements.

Atomically Precise Insights into Metal–Metal Bonds Using Comparable Endo-Units of Sc_(2) and Sc_(2)C_(2)

The precise identification of metal-metal bonds is critical to fully understanding the nature of metal-metal bonding but remains a fundamental challenge.Herein,we show the essence of Sc-Sc bonds with a metal-metal distance of 3.36 Å in a C_(3v)(8)-C_(82) fullerene cage using crystallography.