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

A new calcium-based Room temperature Stable Electride (RoSE), K[{Ca[N(Mes)(SiMe₃)]₃(e)}₂K₃] (2), is successfully synthesized from the reaction of a calcium tris-amide, [Ca{N(Mes)(SiMe₃)}₃K] (1) (Mes = 2,4,6-trimethylphenyl), with potassium under mechanochemical treatment. The dimeric structure of K[{Ca[N(Mes)(SiMe₃)]₃(e)}₂K₃] 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(η⁶-C₆H₆)₄][{Ca[N(Mes)(SiMe₃)](H)}₂K₃] (3). Computational DFT analysis reveals the crucial role played by the ligand framework in the stabilization of this new Ca-hydride complex.