On the Structure of the Cation N2H with an NH ċ N Hydrogen Bond in the Monoammonia Adduct of Ammonium Iodide

In spite of the great importance of the NH ċ N hydrogen bridge in chemistry and biochemistry, the solid‐state structure of the simplest system containing this bond, [H3NH ċ NH3]⊕, was previously unknown. Single crystal X‐ray diffraction studies on NH4I · NH3 have shown that the interaction NH ċ NH3 leads to the formation of the cation N2H . The N  N distance determined by least squares refinement is 269(5) pm, somewhat shorter than the equilibrium distance of 273.1 pm calculated in 1982 by Scheiner and Harding.