Spontaneous H2 Loss through the Interaction of Squaric Acid Derivatives and BeH2 |
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Authors: | Dr. M. Merced Montero‐Campillo Prof. Manuel Yáñez Dr. Al Mokhtar Lamsabhi Prof. Otilia Mó |
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Affiliation: | Departamento de Química, Facultad de Ciencias, Módulo 13, Universidad Autónoma de Madrid, Campus de Excelencia UAM‐CSIC, Cantoblanco, 28049 Madrid (Spain), Fax: (+34)?91‐497‐5238 |
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Abstract: | The most stable complexes between squaric acid and its sulfur‐ and selenium‐containing analogues (C4X4H2; X=O, S, Se) with BeY2 (Y=H, F) were studied by means of the Gaussian 04 (G4) composite ab initio theory. Squaric acid derivatives are predicted to be very strong acids in the gas phase; their acidity increases with the size of the chalcogen, with C4Se4H2 being the strongest acid of the series and stronger than sulfuric acid. The relative stability of the C4X4H2 ? BeY2 (X=O, S, Se; Y=H, F) complexes changes with the nature of the chalcogen atom; but more importantly, the formation of the C4X4H2 ? BeF2 complexes results in a substantial acidity enhancement of the squaric moiety owing to the dramatic electron‐density redistribution undergone by the system when the beryllium bond is formed. The most significant consequence of this acidity enhancement is that when BeF2 is replaced by BeH2, a spontaneous exergonic loss of H2 is observed regardless of the nature of the chalcogen atom. This is another clear piece of evidence of the important role that closed‐shell interactions play in the modulation of physicochemical properties of the Lewis acid and/or the Lewis base. |
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Keywords: | beryllium chalcogens cooperative phenomena hydrogen noncovalent interactions |
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