Mechanochemical Synthesis, Characterization and Reactivity of a Room Temperature Stable Calcium Electride

Abstract

A new calcium-based Room temperature Stable Electride (RoSE), K[{Ca[N(Mes)(SiMe 3 )] 3 (e − )} 2 K 3 ] (2), is successfully synthesized from the reaction of a calcium tris-amide, [Ca{N(Mes)(SiMe 3 )} 3 K] (1) (Mes = 2,4,6-trimethylphenyl), with potassium under mechanochemical treatment. The dimeric structure of K[{Ca[N(Mes)(SiMe 3 )] 3 (e − )} 2 K 3 ] is calculated using ab initio random structure searching (AIRSS) methods. This shows the existence of highly localized anionic electrons (e − ) and suggests poor electrical conductance, as confirmed via electroconductivity measurements. The two anionic electrons in 2 are strongly antiferromagnetically coupled, thus in agreement with the largely diamagnetic response from magnetometry. Reaction of 2 with pyridine affords 4,4′bipyridine, while reaction with benzene gives C−H activation and formation of a calcium hydride complex, [K(η 6 -C 6 H 6 ) 4 ][{Ca[N(Mes)(SiMe 3 )](H)} 2 K 3 ] (3). Computational DFT analysis reveals the crucial role played by the ligand framework in the stabilization of this new Ca-hydride complex.