Ligand influences on the structures of molybdenum oxide networks

The influence of organonitrogen Ligands on the network structure of molybdenum oxides was examined by preparing three new molybdenum oxide phases [MoO3(4,4'-bpy)(0.5)] (MOXI-8), [HxMoO3(4,4'-bpy)(0.5)] (MOXI-9) and [MoO3-(triazole)(0.5)] (MOXI-32). The structure of [MoO3(4,4'-bpy)(0.5)] consists of layers of corner-sharing MoO5N octahedra, buttressed by bridging 4,4'-bipyridyl ligands into a three-dimensional covalently bonded organic-inorganic composite material. Partial reduction of [MoO3(4,4'-bpy)(0.5)] yields the mixed-valence material [HxMoO3(4,4'-bpy)(0.5)] (x approximate to 0.5). The most apparent structural change upon reduction is found in the Mo-ligand bond lengths of the MoO5N octahedra, which exhibit the usual (2 + 2 + 2) pattern in [MoO3(4,4'-bpy)(0.5)] and a more regular (5 + 1) pattern in [HxMoO3(4,4'-bpy)(0.5)]. Substitution of triazole for 4,4'-bipyridine yields [MoO3(triazole)(0.5)], which retains the layer motif of corner-sharing MoO5N octahedra but with distinct sinusoidal ruffling in contrast to planar layers of [MoO3(4,4'-bpy)(0.5)] and [HxMoO3(4,4'-bpy)(0.5)]. The folding reflects the ligand constraints imposed by the triazole ligand that bridges adjacent Mo sites within a layer. MOXI-8, C5H4NMoO3: monoclinic P2(1)/c, a = 7.5727(6) Angstrom, b = 7.3675(7) Angstrom, c = 221433(3) Angstrom, beta = 90.396(8)degrees, Z = 8. MOXI-9, C5H4.5NMoO3: monoclinic I2/m, a = 5.2644(4) Angstrom, b = 5.2642(4) Angstrom, c = 22,730(2) Angstrom, beta = 90.035(1)degrees, Z = 4. MOXI-32, C2H3N3Mo2O6: orthorhombic Pbcm, a = 3.9289(5) Angstrom, b = 13.850(2) Angstrom, c = 13.366(2) Angstrom, Z = 4.