Structure, Deprotonation Energy, and Cation Affinity of an Ethynyl-Expanded Cubane

The ethynyl-expanded cubane 2 is examined at the B3LYP/6-31G* level for its structure, ring-strain energy, deprotonation energy, and affinity toward lithium and sodium cation. The estimate of the ring-strain energy of 2 is 48.3 kcal mol-1. Its free energy of deprotonation is 325 kcal mol-1. Lithium cation coordinates to the face of 2, while sodium coordinates to the cage center. These properties are compared with those of simple acyclic alkynes and cyclododeca-1,4,7,10-tetrayne, the analogue of the face of 2.