A Tetraethynyl[5]cumulene

The first example of a new class of carbon‐rich molecules is introduced, namely, a derivative of tetraethynyl[5]cumulene (TE5C). The use of sterically demanding pendent groups is the decisive structural feature to provide a stable product. Whereas triisopropylsilyl groups are seemingly not sufficiently large to afford an isolable cumulene product, switching to the larger tris(3,5‐di‐ tert ‐butylphenyl)methyl (‘supertrityl’) groups gives a crystalline, stable compound ( [5]TE ). The structural and electronic properties of [5]TE are examined in comparison to its closest known molecular relatives, tetraaryl[5]cumulenes.