A while ago, I explored how the 3-coordinate halogen compound ClF ₃ is conventionally analyzed using VSEPR (valence shell electron pair repulsion theory). Here I (belatedly) look at other such tri-coordinate halogen compounds using known structures gleaned from the crystal structure database (CSD). The search query specifies 7A as the central atom, defined with just three bonded (non-metallic) atoms.

Previously, I explored deviation from ideal tetrahedral arrangements of four carbon ligands around a central (sp ³ ) carbon using crystal structures. Now it is the turn of digonal (sp ¹ ) and trigonal (sp ² ) carbons.  Firstly, the digonal C≡C case. Attached to each carbon of the C≡C unit are two saturated carbon ligands; this to prevent conjugation from influencing our result.