The oxidation of phosphorus by sulfur at low temperatures (<100 °C) has been shown to produce complex mixtures that include 12 of the 17 known binary phosphorus sulfides. Two of these 17 sulfides have been observed in these mixtures for the first time. The rate-determining and first step in the reaction appears to be the formation of the S8 diradical. This proposal is supported by the observed rate at which the sulfides are formed and the distribution of the sulfide product stoichiometries. Photoinitiation of this oxidation at 0 °C produces a similar array of sulfides. The differences in the product distributions between the thermal and photochemical processes facilitate the understanding of the mother−daughter relationships between the products. The effects of oxidation by sulfur and reduction by phosphorus have been determined for several of the known phosphorus sulfides. The characterizations of phosphorus compounds in molten mixtures of phosphorus and sulfur were performed by 31P NMR and Raman spectroscopy directly on the reaction mixtures.
The oxidation of elemental phosphorus (P4) by elemental sulfur (S8) has been studied by a combination of 31P nmr and Raman spectroscopic techniques. At temperatures below the auto-ignition temperature, a molten mixture of the elements gives rise to a complex mixture of products which are dominated by phosphorus sulfides which have a high S/P4 ratio. Both the rate at which the products are formed and their distribution support the formation of a reactive P4S8 intermediate which then cascades through a series of reactions, incorporating the sulfur atoms into the phosphorus cage. Two new phosphorus sulfides (of composition P4S6 and P4S8) have been identified in these product mixtures. INTRODUCTION EXPERIMENTAL PROCEDUREAll reactions were performed either under vacuum or dry, oxygen free nitrogen using standard Schlenk techniques. The purity of the phosphorus (commercial vs. distilled) did not appear to affect the outcome of the chemistry.The Raman spectroscopy experiments were performed by observing reaction mixtures through a quartz flat sealed to the bottom of a mechanically stirred quartz reaction vessel. The reaction zone was a cylinder 2 cm long and 1 cm in diameter , heated with nichrome wire wound around the cylinder. The spectra were recorded using a fiber optic probe placed in contact with the quartz flat. The reaction was profiled by recording spectra at regular intervals over the course of 8-24 hours, depending on the mixture and the reaction temperature. 31P nmr spectroscopy was performed at 300 and 400 MHz (proton frequency) in standard 5 mm tubes. All reaction mixture nmr tubes were sealed under moderate vacuum (10-12 mmHg total pressure).
Products and Mechanisms in the Oxidation of Phosphorus by Sulfur at Low Temperature.-Oxidation of phosphorus by sulfur at temp. below 100 • C yields complex mixtures of phosphorus sulfides containing 10 of the 17 known binary phosphorus sulfides and the two novel sulfides, γ-P 4 S 6 (I) and γ-P 4 S 8 of the proposed structure (II). The phosphorus compounds in the molten mixtures are characterized by 31 P NMR and Raman spectroscopy directly on the reaction mixtures. The first slow step in the reaction, which can be initiated thermally at ≥ 80 • C or photochemically at low temp., seems to be the formation of the diradical · S-S 6 -S · by S-S bond cleavage. Mechanistic explanations for the initially formed product distribution in the low temp.(80 • C) reaction of P 4 and S 8 are discussed.-(JASON, M. E.; NGO, T.; RAHMAN, S.; Inorg.
Insoluble inorganic glasses are difficult to study as molecular structures. The science of soluble phosphate glasses is highly advanced and can serve as pilots for other systems. Anhydrous amorphous aluminum condensed phosphate and insoluble silicate glasses are examples of difficult systems. Anhydrous amorphous condensed phosphates in the molar composition range 0.0 Al2O3/P2O5•…0.5 were prepared. Some physical properties were studied as a function of compositions and treatments. Amorphous aluminum condensed phosphates are ionic-covalent polymers as demonstrated in classical phosphate glass theory.
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