The 1 : 1 adduct of triphenylsilanol and 4,4 '-bipyridyl, and three pairwise-concomitant triclinic polymorphs of the 4 : 1 adduct having Z ' = 0.5, 1 and 4

Crystallization from methanol solution of mixtures of triphenylsilanol and 4,4'-bipyridyl has given a 1: 1 adduct ( I), Ph3SiOH.C10H8N2, and three polymorphic 4: 1 adducts (II) - (IV), (Ph3SiOH)(4).C10H8N2. In (I), the components are linked by a single O-H...N hydrogen bond and by a number of C-H...pi(arene) hydrogen bonds to form a continuous three-dimensional structure. Compounds ( II) -( IV) are all triclinic, space group P (1) over bar, with Z' values of 0.5, 1 and 4, respectively. The basic hydrogen-bonded aggregate is the same in each of ( II) - ( IV), having a pair of silanol molecules linked to the bipyridyl via O-N...N hydrogen bonds and a further pair of silanol molecules linked to the first pair via O-H...O hydrogen bonds. In ( II) there is just one such aggregate lying across a centre of inversion (Z' = 0.5) and in (III) there are two such aggregates, both lying across centres of inversion (Z' = 2 x 0.5 = 1). In ( IV) there are six independent aggregates of this type, four of which lie across centres of inversion and two of which lie in general positions, so that Z' = (4 x 0.5) + 2 = 4. While the components in ( I) are fully ordered, each of ( II) -( IV) exhibits extensive disorder involving both the bipyridyl units and the phenyl rings of the silanol components.