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

ABSTRACT

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.

GRAPHICAL ABSTRACT

KEYWORDS:

• Hydrogen storage
• oxyacid beryllium derivatives
• angular strain
• ab initio calculations

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials.

ORCID

Ibon Alkorta http://orcid.org/0000-0001-6876-6211

M. Merced Montero-Campillo http://orcid.org/0000-0002-9499-0900

José Elguero http://orcid.org/0000-0002-9213-6858

Manuel Yáñez http://orcid.org/0000-0003-0854-585X

Otilia Mó http://orcid.org/0000-0003-2596-5987

Additional information

Funding

This work was carried out with financial support from the Comunidad Autónoma de Madrid (Project FOTOCARBON, ref. S2013/MIT-2841), from the Ministerio de Economía, Industria y Competitividad (Projects No. CTQ2015-63997-C2 and CTQ2016-76061-P) and from the COST Action CM1204. Storage and computational resources from CTI (CSIC) and Centro de Computación Científica (CCC, UAM) are gratefully acknowledged.