Yu Pengyuan, Bao Lipiao, Yang Le, Hao Debo, Jin Peng, Shen Wangqiang, Fang Hongyun, Akasaka Takeshi, Lu Xing
State Key Laboratory of Materials Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan 430074 China.
School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 China.
Inorg Chem. 2020 Jul 6;59(13):9416-9423. doi: 10.1021/acs.inorgchem.0c01304. Epub 2020 Jun 17.
Fullerene cages are ideal hosts to encapsulate otherwise unstable metallic clusters to form endohedral metallofullerenes (EMFs). Herein, a novel TiC cluster with two titanium atoms bridged by a C-unit has been stabilized by three different fullerene cages to form TiC@(5)-C, TiC@(8)-C, and TiC@(6)-C, representing the first examples of unsupported titanium carbide clusters. Crystallographic results show that the configuration of the TiC cluster changes upon cage variation. In detail, the TiC cluster adopts a butterfly shape in TiC@(8)-C and TiC@(6)-C with Ti-C-Ti dihedral angles of 156.35 and 147.52° and Ti-Ti distances of 3.633 and 3.860 Å, respectively. In sharp contrast, a stretched planar geometry of TiC is observed in TiC@(5)-C, where a Ti-C-Ti angle of 176.87° and a long Ti-Ti distance of 5.000 Å are presented. Consistently, theoretical calculations reveal that the cluster configuration is very sensitive to the cage shape which eventually determines the electronic structures of the hybrid EMF-molecules, thus adding new insights into modern coordination chemistry.
富勒烯笼是封装原本不稳定的金属簇以形成内嵌金属富勒烯(EMF)的理想主体。在此,一种由一个C单元桥接两个钛原子的新型TiC簇已被三种不同的富勒烯笼稳定化,形成TiC@(5)-C、TiC@(8)-C和TiC@(6)-C,代表了无支撑碳化钛簇的首个实例。晶体学结果表明,TiC簇的构型随笼的变化而改变。具体而言,TiC簇在TiC@(8)-C和TiC@(6)-C中呈蝶形,Ti-C-Ti二面角分别为156.35°和147.52°,Ti-Ti距离分别为3.633 Å和3.860 Å。形成鲜明对比的是,在TiC@(5)-C中观察到TiC呈拉伸的平面几何构型,其中Ti-C-Ti角为176.87°,Ti-Ti距离为5.000 Å。一致地,理论计算表明簇构型对笼形状非常敏感,最终决定了混合EMF分子的电子结构,从而为现代配位化学增添了新的见解。