Metal hydrides as sodium bond acceptors: hydride-sodium bond in the XH ··· NaH (X = HBe, LiBe, NaBe, HMg, LiMg, and NaMg) complexes

Abstract

New kinds of sodium bonding complexes XH ··· NaH (X = HBe, LiBe, NaBe, HMg, LiMg, and NaMg) have been predicted and characterized in the present paper. For each XH ··· NaH complex, the hydride-sodium bond is formed between the negatively charged H atom of XH and the positively charged Na atom of NaH. Due to the formation of the complexes, both the X–H and the Na–H bonds are elongated, and the Na–H stretching vibrational frequency is redshifted. The interaction energies in the XH ··· NaH complexes at the MP2/6-311++G(3df, 3pd) level increased in the order: HBeH ··· NaH (−4.50 kcal/mol) < HMgH ··· NaH (−8.69 kcal/mol) < LiBeH ··· NaH (−11.07 kcal/mol) < NaBeH ··· NaH (−11.38 kcal/mol) < LiMgH ··· NaH (−14.90 kcal/mol) < NaMgH ··· NaH (−15.35 kcal/mol). It is found that, the more metallicity of the X part in the XH molecule, the stronger sodium bond interaction between XH and NaH. By comparisons with some related systems, it is concluded that the strength of hydridic H bond is increased in the order: dihydrogen bond < hydride-sodium bond < lithium–Hydride lithium bond.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant No. 21173095).