Synthesis and Characterization of Reduced Scandium Halide Containing One- and Two-Dimensional Metal Bonded Arrays

摘要

The stabilization effect of metal-metal bond formation on reduced scandium compounds was studied. The binary compounds Sc sub 7 Cl sub 12 , Sc sub 5 Cl sub 8 , Sc sub 7 Cl sub 10 and ScCl were prepared by high temperature techniques and were characterized by single crystal x-ray diffraction. The respective metal arrays in these compounds can be viewed as fragments of scandium metal ranging from discrete six atom metal cluster species (Sc(Sc sub 6 Cl sub 12 )), through intermediate single and double infinite chain configurations ((ScCl sub 2 )(Sc sub 4 Cl sub 6 )) and ((ScCl sub 2 )(Sc sub 6 Cl sub 8 )) to double metal close-packed sheets (ScCl). The halogen atoms effectively isolate the clusters, chains and sheets by bonding face, edge or exo positions on the metal arrays. The common occurrence of isolated scandium (III) ions emphasizes that a minimum number of bonding electrons is required to stabilize what are formally anionic metal arrays. The distribution of the reduction electrons in these anisotropic materials was studied by magnetic susceptibility, EPR and uv-X photoelectron spectroscopy. The ternary compounds studied were Cs sub 3 Sc sub 2 Cl sub 9 and CsScCl sub 3 . The anion-bridged metal chain of the hexagonal perovskite structure was found to stabilize scandium (II). CsScCl sub 3 was found to be grossly nonstoichiometric on the transition metal site and the effects of the mixed valence character were studied between the single valence extremes Cs sub 3 Sc/sub 2 + x/Cl sub 9 ; 0