Single-crystal synthesis of low-valency molybdenum compounds by slow cooling of electrolyzed Li₂MoO₄MoO₃ melts

Li₂MoO₄MoO₃ melts in Al₂O₃ crucibles were electrolyzed at 650°C and then slowly cooled to obtain crystals of the reduced molybdates formed. Crystallization occurred throughout the melt and not on the electrodes. In addition to MoO₂ and the known bronze Li_0.33MoO₃, single crystals of three new compounds have been identified: (1) Li₂Al₂Mo₄O₁₅ triclinic; a = 6.636 ± 0.002 Å, b = 7.158 ± 0.002 Å, c = 7.055 ± 0.002 Å, α = 90.95 ± 0.03°, β = 105.32 ± 0.03°, γ = 110.9 ± 0.03°; (2) Li_1.3Mo₃O₈, triclinic; a = 8.256 ± 0.006 Å, b = 8.550 ± 0.007 Å, c = 11.36 ± 0.01 Å, α = 96.7 ± 0.1°, β = 70.5 ± 0.1°, γ = 87.5 ± 0.1°; (3) Li_0.1Mo₄O₇, orthorhombic, space group Pbnb, a = 7.475 ± 0.007 Å, b = 24.94 ± 0.07 Å, c = 29.4 ± 0.1 Å. The formation of these compounds depends on the composition of the melt and the duration of electrolysis. There is some evidence that these compounds are not products of electrode reactions but are formed by secondary reactions in the melt between the primary products of electrolysis.