Detalle de: Complexes between H2 and neutral oxyacid beryllium derivatives. The role of angular strain

The complexes between 14 different Be-salts of oxyacids from groups 13 to 16 with one and two molecules of H2 have been investigated by means of the MP2/aug-cc-pVTZ ab initio molecular orbital theory method, which was found to be reliable for the treatment of these weakly bound species. The main conclusion is that these Be-salts yield rather stable complexes with dihydrogen, with binding energies one order of magnitude larger than other typical H2 complexes reported in the literature. This strong binding is shown to be due to an enhancement of the electron-deficient nature of Be when attached to an oxyacid moiety, which depends more on the type of coordination of the central atom of the oxyacid moiety. The formation of these complexes is followed by a significant lengthening of the H2 internuclear distance and a concomitant red-shift of the H–H stretching frequency, which becomes a good indicator of the strength of the interaction. The charge shifting from the bonding region of the H2 molecule to the interboundary Be···H2 region is the physical phenomenon behind the stability of these complexes. Accordingly, the most important contributor to this stability is the inductive term, followed by the electrostatic interactions. The ability of Be to bind H2 is enhanced by the angular arrangement of the O–Be–O electron-acceptor group.