The smallest bond angle in ClF4 (chlorine tetrafluoride) is approximately 81.2 degrees. This angle corresponds to the F-Cl-F bond angle, which is formed between the fluorine atoms on the axial positions of the molecular geometry.
To explain further, ClF4 has a square planar molecular geometry. In this structure, chlorine is the central atom surrounded by four fluorine atoms and two lone pairs of electrons. The two lone pairs are positioned opposite each other to minimize repulsion, which leads to a square planar arrangement of the four fluorine atoms. The bond angles between the axial fluorine atoms are compressed slightly due to the presence of the lone pairs, making the bond angles a bit less than the ideal 90 degrees found in a perfect square planar arrangement. As a result, the smallest bond angle found in ClF4 is approximately 81.2 degrees.