Unconventional Ionic Hydrogen Bonds. 2. NH(1+)...? Complexes of Onium Ions with Olefins and Benzene Derivatives

Article abstract of DOI:10.1021/ja00288a034

Unconventional strong ionic hydrogen bonds of the -XH(1+)...? type, where the electron donor is a ?-bond or an aromatic ?-system, are formed in the clustering reactions of NH4(1+) and MeNH3(1+) with C2H4 and benzene derivatives.The interaction energies range from 10 to 22 kcal mol^-1.The experimental results and ab initio calculations on C2H4*NH4(1+), C6H6*NH4(1+), and C6H5F*NH4(1+) indicate that the interaction is primarily electrostatic in nature with little ?-donation into the bond.The most stable structure of C2H4*NH4(1+) is the conformer where one N-H(1+) bond points at the center of the double bond.For C6H6*NH4(1+) and C6H5F*NH4(1+), the lowest energy ?-dimers have two NH4(1+) hydrogens directed towards the ring.The F...H-NH3(1+) ?-complex was studied also for C6H5F*NH4(1+).The latter complex is the more stable of the two at this level of calculation.