Structure and Properties of La(2)Mo(2)0(7), a Quasi-Two dimensional metallic oxide with strong Mo-Mo bonds.

Single crystals of La(2)Mo(2)0(7), prepared by fused salt *electrolysis, were used for structural and electronic characterization. La (2)mo(2)0(7) is orthorhombic with a=6.034A, b=12.236A and c=3. 888A. The dominant feature of the structure, which was refined in space group Pnnm, is Mo(2)0(10) units formed by edge sharing Mo0(6) octahedra which contain Mo-Mo distances of only 2,478A, the shortest yet reported for molybdenum oxide systems. These groups then share corners in two dimensions to give rise to Mo-0 layers which are held together by the lanthanum ions. The relationship of the La(2)Mo(2)0(7) structure to those of other reduced oxides is discussed. La(2)mo(2)0 (7) is a metallic conductor down to 125K where a phase transition takes place. A similar transition is seen in the magnetic susceptibility. The anamolous electric and magnetic behavior of this compound may be associated with a charge density wave instability of the type often found in quasi two-dimensional materials.