Abstract: | Molecular squares are among the most common supramolecular architectures, but phospha‐organometallic complexes have not been used as building blocks for this type of structure. Herein we describe the formation of the molecular square [Au{Co(P2C2tBu2)2}]4 ( 1 ) by the self‐assembly of anionic 1,3‐diphosphacyclobutadiene cobalt complexes and gold(I) cations. The X‐ray crystallographic determination of the molecular structure of 1 is complemented by solid‐state 31P and 13C NMR investigations. High‐level DFT calculations confirm the assignment of the 31P and 13C NMR resonances. |