Some reduced ternary and quaternary oxides of molybdenum. A family of compounds with strong metal-metal bonds

Several new, reduced ternary and quaternary oxides of molybdenum are reported, each containing molybdenum in an average oxidation state <4.0. All are prepared by reactions between a molybdate salt; metal oxide, if needed; and MoO2 sealed in Mo tubes held at 1100°C for ca. 7 days. Refinement of the substructure of the new compound Ba0.62Mo4O6 was based on an orthorhombic cell, witha = 9.509(2), b = 9.825(2), c = 2.853(1)Å, Z = 2 in space groupPbam; weak supercell reflections indicate the true structure hasc = 8(2.853) Å. The chief structural feature is closely related to that of NaMo4O6 (C. C. Torardi, R. E. McCarley,J. Amer. Chem. Soc.101, 3963 (1979)), which consists of infinite chains of Mo6 octahedral clusters fused on opposite edges, bridged on the outer edges by O atoms and crosslinked by MoOMo bonding to create four-sided tunnels in which the Ba2+ ions are located. The structure of Ba1.13Mo8O16 is triclinic,a = 7.311(1), b = 7.453(1), c = 5.726(1)Å, α = 101.49(2), β = 99.60(2), γ = 89.31(2)°,Z = 1, space groupP1¯. It is a low-symmetry, metal-metal bonded variant of the hollandite structure, in which two different infinite chains, built up from Mo4O2−8 and Mo4O0.26−8 cluster units, respectively, are interlinked via MoOMo bridge bonding to create again four-sided tunnels in which the Ba2+ ions reside. Other compounds prepared and characterized by analyses and X-ray powder diffraction data arePbxMo4O6(x ∼ 0.6), LiZn2Mo3O8, CaMo5O8, K2Mo12O19, and Na2Mo12O19.