Strontium Phosphide (12504-16-4) Physical and Chemical Properties
Strontium Phosphide
Highly reactive inorganic phosphide used in specialized R&D and manufacturing applications, requiring dry handling and controlled environments due to its water reactivity.
| CAS Number | 12504-16-4 |
| Family | Alkaline earth metal phosphides |
| Typical Form | Powder or crystalline solid |
| Common Grades | EP, USP |
Strontium phosphide is an inorganic binary phosphide of an alkaline-earth metal; it belongs to the class of metal phosphides and exists as an ionic/crystalline solid with nominal stoichiometry \(\mathrm{Sr}_3\mathrm{P}_2\). Structurally it can be considered a lattice composed of multiply charged strontium cations and phosphide anions, formally represented by \(\mathrm{Sr}^{2+}\) and \(\mathrm{P}^{3-}\) species in a 3:2 ratio. Electronically, the phosphide anion is highly reducing and carries localized lone-pair character on phosphorus, while the strontium centers provide charge balance and lattice stabilisation; this combination yields a material that is strongly basic at the anion site and prone to redox and hydrolytic reactivity.
Chemically, metal phosphides such as strontium phosphide are water-reactive and act as strong reducing agents. Hydrolysis or acidification of the solid generates phosphine gas (\(\mathrm{PH}_3\)), a flammable and highly toxic gaseous product; hydrolysis also produces metal hydroxide species in solution, leading to corrosive, alkaline conditions. In air or on heating the material can decompose, emitting phosphorus oxides and other toxic fumes; it is generally incompatible with oxidizers and strong acids, and can ignite on contact with moisture. Because of these hazards, handling and use require strict moisture exclusion and appropriate protective measures.
Technically, strontium phosphide finds niche use as a laboratory reagent and as a component in devices that exploit controlled water-reactivity or solid-state phosphide chemistry. Its reactivity profile (water-reactive, reducing, pyrophoric tendencies in finely divided forms) governs selection for applications where in‑situ generation of reactive phosphorus species or high chemical reactivity is required. Common commercial grades reported for this substance include: EP, USP.
Basic Physical Properties
Density
No experimentally established value for this property is available in the current data context.
Melting or Decomposition Point
The material does not exhibit a simple melting transition under usual conditions; the experimental property reported is "Decomposes." On heating to decomposition it emits toxic fumes including phosphorus oxides, consistent with thermal breakdown of the phosphide lattice.
Solubility in Water
No experimentally established value for this property is available in the current data context.
Solution pH (Qualitative Behavior)
Contact of strontium phosphide with water or moisture results in rapid hydrolysis, producing phosphine gas (\(\mathrm{PH}_3\)) and strontium hydroxide species. The resulting aqueous phase is expected to be strongly alkaline and corrosive because of hydroxide formation; concurrent evolution of \(\mathrm{PH}_3\) poses an acute inhalation and flammability hazard.
Chemical Properties
Acid–Base Behavior
Strontium phosphide contains the strongly basic phosphide anion (\(\mathrm{P}^{3-}\)). In the presence of acids or protic media the anion is protonated to form phosphine (\(\mathrm{PH}_3\)), a volatile, flammable, and highly toxic gas. The solid is therefore acid-sensitive and reacts vigorously with acids; neutralization or acid contact is contraindicated unless carried out in controlled, ventilated laboratory conditions with appropriate capture of gases.
Reactivity and Stability
The substance is water‑reactive and a strong reducing agent. It is reactive or pyrophoric on exposure to moisture and may ignite spontaneously on contact with water or moist air in some circumstances. It is incompatible with oxidizing agents and strong acids, which can lead to violent reactions. Thermal decomposition evolves phosphorus oxides and other toxic fumes. In solid form it should be regarded as chemically unstable toward protic and oxidizing environments and handled under dry, inert conditions.
Molecular and Ionic Parameters
Formula and Molecular Weight
- Molecular formula: \(\mathrm{Sr}_3\mathrm{P}_2\) (also recorded as P2Sr3)
- Molecular weight: 324.8
- Exact mass: 325.6643608
- Monoisotopic mass: 325.6643608
Additional computed descriptors: Topological polar surface area = 0; heavy atom count = 5; formal charge = 0; H-bond donor count = 0; H-bond acceptor count = 2; rotatable bond count = 0.
SMILES: [P-3].[P-3].[Sr+2].[Sr+2].[Sr+2]
InChI: InChI=1S/2P.3Sr/q2-3;3+2
InChIKey: ATAJSUOOOWSVGL-UHFFFAOYSA-N
Constituent Ions
Stoichiometry is three strontium cations and two phosphide anions per formula unit, providing overall electrical neutrality: 3 × \(\mathrm{Sr}^{2+}\) and 2 × \(\mathrm{P}^{3-}\). The phosphide anion is the chemically reactive site responsible for hydrolysis to \(\mathrm{PH}_3\) and for strong reducing behavior.
Identifiers and Synonyms
Registry Numbers and Codes
- CAS number: 12504-16-4
- EC number: 235-678-9
- UN number (shipping identifier): UN 2013 (Strontium phosphide)
- DSSTox Substance ID: DTXSID30894176
- Wikidata: Q4492130
- InChI: InChI=1S/2P.3Sr/q2-3;3+2
- InChIKey: ATAJSUOOOWSVGL-UHFFFAOYSA-N
- SMILES: [P-3].[P-3].[Sr+2].[Sr+2].[Sr+2]
Synonyms and Common Names
Common synonyms and designations reported include: - Strontium phosphide - Strontium phosphide (Sr3P2) - Tristrontium diphosphide - tristrontium bis(phosphorus(3-)) - Tristrontium;phosphorus(3-)
(These names are used interchangeably in vendor and scientific contexts to designate the \(\mathrm{Sr}_3\mathrm{P}_2\) composition.)
Industrial and Commercial Applications
Functional Roles and Use Sectors
Strontium phosphide is used as a specialty laboratory reagent and in the manufacture of chemically reactive devices where controlled generation of phosphorus-containing species or strong reducing behavior is required. Its primary technical role is as a source of phosphide reactivity in solid‑state and synthetic applications; selection is driven by the material's water‑reactive and reducing characteristics. Reported commercial grades include: EP, USP. The substance has an inactive commercial activity status in one inventory listing (noting that commercial availability and regulatory status vary by jurisdiction).
Typical Application Examples
Typical, high‑level application contexts are: reagent for research-scale syntheses involving phosphide chemistry, and incorporation into devices or assemblies that exploit water‑reactive or reducing properties. Use is restricted to operations with engineering controls and emergency provisions that address the generation of phosphine and corrosive by-products.
Safety and Handling Overview
Health and Environmental Hazards
Strontium phosphide is a water‑reactive inorganic phosphide that liberates phosphine (\(\mathrm{PH}_3\)) on contact with water or acids. Phosphine is flammable and highly toxic by inhalation; exposure can be life-threatening. Hydrolysis can also produce corrosive alkaline solutions (metal hydroxides). Environmental release or firefighting runoff may cause contamination; combustion or decomposition generates irritating, corrosive and toxic phosphorus oxides.
Acute exposure guideline levels for the phosphine hydrolysis product are reported as follows (units as reported: ppm):
- 10 min: AEGL‑1: NR; AEGL‑2: \(2.0\,\mathrm{ppm}\); AEGL‑3: \(3.6\,\mathrm{ppm}\)
- 30 min: AEGL‑1: NR; AEGL‑2: \(2.0\,\mathrm{ppm}\); AEGL‑3: \(3.6\,\mathrm{ppm}\)
- 60 min: AEGL‑1: NR; AEGL‑2: \(1.0\,\mathrm{ppm}\); AEGL‑3: \(1.8\,\mathrm{ppm}\)
- 4 hr: AEGL‑1: NR; AEGL‑2: \(0.25\,\mathrm{ppm}\); AEGL‑3: \(0.45\,\mathrm{ppm}\)
- 8 hr: AEGL‑1: NR; AEGL‑2: \(0.13\,\mathrm{ppm}\); AEGL‑3: \(0.23\,\mathrm{ppm}\)
First‑aid and emergency measures for exposures emphasize immediate removal from exposure, oxygen support for respiratory compromise, prolonged flushing of skin or eyes with water, and urgent medical treatment for suspected phosphine inhalation or chemical burns. If ingestion or significant inhalation is suspected, do not induce vomiting; obtain emergency medical care and inform responders of the phosphide/phosphine hazard.
Storage and Handling Considerations
- Store under dry, inert atmosphere conditions with strict exclusion of moisture. Maintain containers tightly closed and protected from sources of ignition and from oxidizing materials and acids.
- Keep material dry during handling, transfer and storage; avoid mechanical forms that produce dust or fine particulates which raise pyrophoric/ignition potential.
- In the event of spills, prevent contact with water or aqueous drains. For solid spills, cover with dry earth or sand and isolate the area; do not use water for cleanup. Containment and cleanup should be performed by trained personnel with appropriate respiratory protection and chemical‑resistant PPE.
- Firefighting: do not apply water directly to burning or hot material where hydrolysis would produce \(\mathrm{PH}_3\); extinguishing options for small fires include dry chemical, dry sand, or lime/soda ash where appropriate. Firefighting and emergency response should employ positive‑pressure respiratory protection and full chemical protective clothing.
- Segregate from acids, oxidizers and other incompatible substances. Monitor storage areas for signs of moisture ingress or container breach. For disposal or long‑term management, consult qualified hazardous‑waste specialists and comply with applicable regulations.
For detailed and product‑specific hazard, transport and regulatory information, users should consult the product Safety Data Sheet (SDS) and applicable local legislation.
