Synthesis and characterization of new reduced scandium chlorides stabilized by interstitial atoms

Abstract

<p>A series of ternary scandium chlorides compounds that contain an interstitial atom in the center of a distorted octahedron of scan- dium atoms have been synthesized in high yield with high tempera- ture techniques. The compounds characterized by single crystal X-ray diffraction have the stoichiometries Sc(,7)Cl(,12)X, Sc(,4)Cl(,6)X, Sc(,5)Cl(,8)Y, Sc(,7)Cl(,10)C(,2), 1T-Sc(,2)Cl(,2)Y, and 3R-Sc(,2)Cl(,2)C (X = B or N; Y = C or N). The respective metal arrays in these compounds can be viewed as fragments of scandium metal ranging from discrete Sc(,6) cluster species Sc Sc(,6)(X)Cl(,6) , through intermediate single and double infinite chain configurations Sc(,4)(X)Cl(,6), (ScCl(,2)) Sc(,4)(Y)Cl(,6) , and (ScCl(,2)) Sc(,6)(C)(,2)Cl(,8) to double metal close-packed sheets Sc(,2)(Y)Cl(,2) , respectively;The stabilizing effect of scandium-interstitial bond formation was studied. Extended Huckel calculations on nonmetal-centered clusters demonstrate that the valence s and p orbitals of the inter- stitial atom interact with four orbitals primarily involved in Sc-Sc bonding to give four low-lying scandium-interstitial bonding orbitals. Other cluster orbitals obtain mainly Sc-Sc bonding character. Band calculation and photoelectron spectroscopy on 1T-Sc(,2)Cl(,2)C suggest the Sc-C covalent bonding. The magnetic susceptibility data of Sc(,7)Cl(,12)B, Sc(,5)Cl(,8)C, and Sc(,7)Cl(,10)C(,2) reveal interesting but complicated magnetic properties;Another series of scandium monochloride hydrides have also been quantitatively synthesized at high temperatures. The compositions are ScClH(,x) (0 < x (LESSTHEQ) 1.0) and M(,z)ScClH(,x) (M = Li, Na, K; 0.1 (LESSTHEQ) z < 0.5; 0.3 (LESSTHEQ) x < 0.9). Two types of structures have been formed in ScClH(,x), ZrBr-type (0 < x < 0.67) and ZrCl-type (x (GREATERTHEQ) 0.67);The X-ray powder diffraction of intercalated M(,z)ScClH(,x) has shown that the ZrBr-type structure is retained for z (LESSTHEQ) 0.1; ('1)DOE Report IS-T-1172. This work was performed in part under contract No. W-7405-Eng-82 with the U.S. Department of Energy.</p>