AbstractThe structures of the two adductsP‐1andQ‐1of bis(1,5‐cyclooctanediyl)diboroxane (1) with pyridine (P) and quinuclidine (Q), which show solid‐„solid”︁ phase transformations at about 127 and 88°C, respectively, have been determined by X‐ray diffraction at −145 and −163°C, respectively. The structure ofQ‐1has also been determined at room temperature and at +50°C. BothP‐1andQ‐1are packed in head‐to‐tail pairs and show extensive isothermal as well as temperature‐dependent dynamics in the crystalline phase. The onset of transformations into the new „fluctional solid”︁ phase is discussed in terms of these lattice packings and the observe