Compared to crown ethers with functions to capture metal cation, inverse crown ethers (ICEs) with a similar cavity architecture have the alternating polarity of cationic metal ring and encapsulated ion to construct the skeleton. Here we introduce a new tridentate aryloxide‐N‐heterocyclic carbene ligand to stabilize μ4‐oxo [Mg4O] cores in ICEs, which open up a path towards synthetic methodology for ICEs. The reaction of N‐Heterocyclic carbene (NHC) lithium complex (L)Li2(L1) (1; L={1‐C(NDippCH2CH2N)}2(CH2)2PhO−, Dipp=2,6‐iPr2‐C6H3; L1=(SiMe3)2N−) with MgBr2 afforded a mixture of (L)Mg2Br3 (2), (L)2Mg4OBr4 (3) and (L)Mg4OBr5(THF)2 (4), via the salt metathesis. Symmetric 3 and unsymmetric 4 including the same μ4‐Oxo [Mg4O] unit possess ICEs character, where O2− atoms lie in the centroid binding to all four Mg2+ centers.

The Cover Feature shows a new inverse‐crown‐ether species appearing with a colorful glow. This glow features a cavity architecture and a bright encapsulated ring to construct the skeleton. The fragment of colorful light looks like the monoanionic bis‐NHC‐pincer‐type ligands and the center of ring is regarded as the core of the [Mg4OBr4] moiety. In our article, we report a tridentate aryloxide‐NHC ligand to obtain a NHC‐magnesium‐bromine adduct, which can further provide access to the inverse crown ethers featuring CNHC‐Mg‐Br moieties and μ4‐oxo [Mg4O] cores. More information can be found in the Full Paper by Y. Li, L. Shen, D. Wu and co‐workers.