Molybdenum and Chlorine

Exploring the Role of Miniemulsion Nanodroplet Confinement on the Crystallization of MoO3: Morphology Control and Insight on Crystal Formation by In Situ Time-Resolved SAXS/WAXS

“…With all synthetic approaches, reaction times shorter than 18 h did not lead to the crystallization of any MoO 3 polymorphs. The formation of several ammonium polyoxomolybdates with different nuclearities, such as (NH 4 ) 4 (Mo 8 O 26 )(H 2 O) 4 , (NH 4 ) 6 (Mo 9 O 30 )(H 2 O) 5 , (NH 4 ) 2 (Mo 3 O 10 ) and (NH 4 ) 2 (Mo 4 O 13 ), characterized by quite big unit cells (i.e., most intense reflections at low Bragg angles, 2 θ < 15°) and constituted by MoO 6 octahedra sharing vertices or edges [ 50 , 51 ], was instead evidenced. Such a finding was expected, as it is well-known from the complex chemistry of polyoxometalates that the acidification of a [MoO 4 ] 2− solution gives rise to polyoxomolybdates, which increase in nuclearity as the pH of the solution decreases, until the most stable product (i.e., the metal oxide itself) is formed [ 38 ].…”

“…Moreover, by following the evolution of the pattern for 5000–10,000 s ( Figure 7 b) it could be appreciated that, with higher amounts of acid, the observed peaks firstly grew, but subsequently their intensity decreased, suggesting the formation and disappearance of a reaction intermediate(s), more stable (i.e., stable for a longer period of time) in the experiments performed with lower amounts of acid (1:10 and 1:15 mol). Such intermediate species could likely be identified in a (mixture of) polyoxomolydate(s), known intermediates in the polycondensation reactions occurring in acidified Mo(VI) solution [ 50 ].…”

Ultraviolet–Visible Absorption Spectroscopy of MoCl5, MoOCl4, and MoO2Cl2 Vapors

“…Solid MoO 3 has a similarly low vapor pressure compared with Mo subchlorides and is not expected to coexist with MoCl 5 in the vapor phase. If fused with MoCl 5 , MoO 3 is reported to participate in the following solid-state reaction M o O 3 + M o C l 5 → M o O C l 3 + M o O 2 normalC l 2 Reaction is reported to be highly exothermic and proceeds at 85 °C to produce the involatile oxytrichloride MoOCl 3 and the highly volatile dioxydichloride MoO 2 Cl 2 . Whether MoO 2 Cl 2 would exist in the presence of excess MoCl 5 is not known, but the reaction between the two species is reported to produce MoOCl 3 and MoOCl 4 , the latter being a volatile oxychloride species.…”

“…Besides existing impurities in MoCl 5 originating from synthesis and purification, there are pathways for impurity generation that could arise during material handling and sample collection. The first such pathway is the thermal decomposition of MoCl 5 at sampling temperature M o C l 5 → M o C l 4 + 1 / 2 normalC l 2 Reaction is reported to occur at temperatures as low as 65 °C and the reaction at 120 °C gives a Cl 2 mole fraction of 9.0% in the vapor . The other decomposition product, MoCl 4 , has a calculated vapor pressure which is ≈7 orders of magnitude lower than MoCl 5 at ≈400 °C .…”

“…The other decomposition product, MoCl 4 , has a calculated vapor pressure which is ≈7 orders of magnitude lower than MoCl 5 at ≈400 °C . Furthermore, MoCl 4 melts incongruously near 277 °C and disproportionates to MoCl 3 and MoCl 5 at temperatures of >127 °C under vacuum. ,, Given the low likelihood of MoCl 4 being present in the vapor phase, Cl 2 is expected to be the main impurity if the thermal decomposition of MoCl 5 is operative during measurements.…”