Experimental and computational studies on solvent-free rare-earth metal borohydrides R (B H4) 3 (R=Y, Dy, and Gd)

Solvent-free trivalent rare-earth metal borohydrides R (B H4) 3 (R=Y, Dy, and Gd) were synthesized from R Cl3 and LiB H4 through solid-state metathesis reactions and characterized by powder x-ray or neutron diffraction measurement and Raman spectroscopy combined with first-principles calculations. The crystal structure of R (B H4) 3 was clarified to adopt a primitive cubic structure with Y (B H4) 3: a=10.852 (1), Dy (B H4) 3: a=10.885 (3), and Gd (B H4) 3: a=10.983 (5) in space group Pa 3̄ (No. 205), the [B H4] - complex anions of which locate on the edges of a distorted cube composed of R3+. Based on the crystal structure, the observed Raman scattering positions are theoretically assigned such that the B H4 bending is at 1050-1300 cm-1 and B H4 stretching is at 2250-2400 cm-1, respectively. In addition, the computational studies on Y (B H4) 3 suggested it to be an insulator that occupied B 2s,2p and H 1s orbitals with little contribution from Y, and the heat of formation was ΔH=-113 kJ mol B H4, which was estimated from (13) Y+B+2 H2 → (13) Y (B H4) 3.