Gas phase dissociation energies of saturated AHn*+ radical cations and AHn neutrals (A = Li-F, Na-Cl): dehydrogenation, deprotonation, and formation of AHn-2*+ - H2 complexes.

Abstract

The dissociation energies corresponding to the two possible A-H cleavages of A (A = Li-F and Na-Cl) radical cations (loss of a H(+) and loss of a H(.)) have been computed at the CCSD(T)/ 6-311++G(3df,2pd) level of theory and compared to those of their neutral precursors. Removing an electron from AH(n)() decreases dramatically its deprotonation energy, especially for the A molecules (C and ), which become one of the most acidic species of the row, their acid character being only exceeded by FH(.+) and ClH(.+), respectively. However, dehydrogenation energies only decrease for the systems on the left side of the row (up to C and SiH(4)(.+)) for which the electron is removed from a A-H bonding orbital. Nevertheless, the loss of hydrogen is the more favorable cleavage in all cases except FH(.+). Ionization of SiH(4) leads to a Jahn-Teller distorted structure that corresponds to a Si - H(2) complex. Other - eta(2)H(2) complexes in the doublet spin state have also been found to be stable for A = Be, Mg, Al, and P, the hydrogen molecule complexes being more stable than their corresponding radical cations, for Be, Mg, and Al.