来源：ACS Publications
Reactions between carbon and lithium hydride in a mixed metal europium/lithium flux led to the synthesis of Eu2Li(C3)H. At room temperature, the compound crystallizes in the tetragonal space group P4/mbm (no. 127, Z = 2; Ca2Li(C3)H type) and undergoes a second-order structural phase transition below ∼250 K to an orthorhombic low-temperature modification (no. 55, Pbam; Z = 4), crystallizing in a new structure type. The phase transition was monitored by using single-crystal X-ray diffraction (SCXRD) and temperature-dependent high-resolution powder diffraction data. Infrared (IR) spectroscopy and gaschromatographic analysis (GC) of the hydrolysis products confirm the existence of a first europium compound with an allylenide anion (C34–). Magnetic susceptibility measurements and 151Eu Mössbauer spectroscopy reveal the presence of divalent europium, suggesting a charge-balanced carbide hydride (Eu2+)2(Li+)(C34–)(H–). A transition to a (soft) ferromagnetic ground state is observed below 42 K. In situ high-pressure, high-temperature (HPHT) investigations indicate a surprisingly high stability of Eu2Li(C3)H and yield a bulk modulus K0 = 65 GPa. Quantum chemical calculations (DFT + U) reveal a pseudogap at the Fermi level and allow the classification as a rare-earth metal Zintl phase exhibiting both ionic and covalent bonding contributions.