Trihydrogen cation

Tlie simplest known example of a 3c-2e bond is that in the trihydrogen cation (H3+), the existence of which, in the gas phase, was first demonstrated... 

Like the dihydrogen cation, hJ, the trihydrogen cation, H, is known only in the gas phase. Both ions have, however, been found in interstellar space. The structure of is that of an equilateral triangle with the three H-H distances equal to 87.5 pm as compared to 74 pm in H2 or 106 pm in hJ. These distances are so short as to imply the existence of three H-H bonds, though the total number of electrons in the molecule is just two The dissociation energy, defined as the energy of the reaction... 

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