The paper reports on the experimental and theoretical investigation of bonding properties of potassium amidoborane, IJKijNH 2 BH 3 ]), which is one of the most promising compounds for hydrogen storage material among metallated derivatives of ammonia borane (NH 3 BH 3 ). For this purpose, in situ Raman spectroscopy, synchrotron X-ray diffraction measurements and complementary ab initio calculations study have been performed under static pressure conditions in the range from ambient pressure up to 25 GPa. Unusual interplay between strong electrostatic and weak dispersive interactions has been revealed, resulting in experimental observation of pressure induced formation of relatively strong conventional hydrogen bonding between negatively charged molecular ions. This finding provides new insight for tailoring materials with desirable properties for various uses.First discovered in 1955, 1 ammonia borane IJNH 3 BH 3 ) has attracted considerable attention as one of the promising candidates for chemical hydrogen storage materials; moreover, it undoubtedly is in the spotlight of this hot research field. 2 High temperatures of hydrogen desorption (from~110 to >300°C) and release of substantial amount of contaminating byproducts are main drawbacks that preclude large-scale practical application of ammonia borane to date. This intensifies experimental efforts, aiming at the destabilization of ammonia borane in order to obtain materials with lower temperature of hydrogen desorption. This is mostly realized by chemical doping or catalysis, usually on the basis of empirical rules or by trial and error method. Moreover, there is still an evident gap in understanding the mechanism beyond the decomposition, better knowledge of which should significantly facilitate the design of new material with reduced emission of unwanted byproducts.Ammonia borane also represents an interesting case of compound, in which dispersive interactions, such as dihydrogen bonds IJN-H δ+ ⋯ δ− H-B), largely define the structure and dynamics of the material at ambient pressure. 3 The dihydrogen bonds, i.e. protonic-hydridic, are known to have strength and directionality comparable with those found in conventional hydrogen-bonded systems. 4,5 Relatively strong dihydrogen bond interaction also plays an important role in decomposition of ammonia borane, allowing dimerization of NH 3 BH 3 molecules and formation of diammoniate of diborane. 6 Recent high-pressure study has revealed a key role of dihydrogen bonds in formation of new polymorphic phases. 7 Ammonia borane derivatives, which are called metal amidoboranes (MAB), have been recently developed as novel hydrogen storage materials, where a cation Me + (Me = Li, Na, etc.) replaces one of the protons (H + ) of the '-NH 3 ' group, leading to the ionic molecular crystal M + ijNH 2 BH 3 ] − . 8,9 Alkali metal amidoboranes (LiNH 2 BH 3 , NaNH 2 BH, KNH 2 BH 3 ) exhibit improved performance with respect to hydrogen desorption. They were recently shown to release 10.9, 7.5, and 6.5 mass% H 2 at temperatures of 80-90...