ON N-H...S HYDROGEN BONDS

A survey of crystals in which NH···S interactions occur leads to the result that most of these systems should be called hydrogen bonds in the sense that this term is usually used. The NH···S distances are in the range 3.25 to 3.55 Å. More important, however, are the observed shortenings of 0.2 to 0.5 Å of the H···S distance under the van der Waals radius sum of 2.75 Å. Small deviations from linearity, i.e. up to about 25 °, of the three atoms involved, may be expected. The possibility of NH···S bonds accordingly should not be overlooked in the construction of models of molecules in which both {A figure is presented}NH groups and sulfur are present. © 1969.