Phosphorus heptabromide

{{for|the pigment code PBr7|List of inorganic pigments#Brown pigments}}

{{Chembox

| ImageFile =Phosphorus heptabromide.svg

| ImageSize =240px

| ImageAlt = Skeletal formula of phosphorus heptabromide

| ImageFile1 = Phosphorus heptabromide ions spacefill.png

| ImageSize1 = 215

| ImageAlt1 = Space-filling models of the ions in phosphorus heptabromide

| IUPACName = Tetrabromophosphanium tribromide

| OtherNames = {{ubl|Perbromophosphonium tribromide|Phosphorus heptabromide|Tetrabromophosphonium tribromide}}

|Section1={{Chembox Identifiers

| CASNo =14337-11-2

| CASNo_Ref = {{cascite|correct|CAS}}

| ChemSpiderID = 57450667

| PubChem = 71308257

| DTXSID = DTXSID60745445

| InChI = 1S/Br4P.Br3/c1-5(2,3)4;1-3-2/q+1;-1

| InChIKey = QBFSXBUUGDHSFY-UHFFFAOYSA-N

| SMILES = Br[P+](Br)(Br)Br.Br[Br-]Br}}

|Section2={{Chembox Properties

| Formula = {{chem2|PBr7}}

| P=1|Br=7

| Appearance = Red prismatic crystals

| Density =

| MeltingPt =

| BoilingPt =

| Solubility = }}

|Section3={{Chembox Structure

| Structure_ref =

| CrystalStruct = Orthorhombic

| SpaceGroup = Pnma, No. 64

| LattConst_a = 9.35 Å

| LattConst_b = 7.94 Å

| LattConst_c = 14.69 Å

}}

|Section4={{Chembox Hazards

| MainHazards =

| FlashPt =

| AutoignitionPt = }}

}}

Phosphorus heptabromide is an inorganic compound with the chemical formula {{chem2|PBr7|auto=1}}. It is one of the phosphorus bromides. At normal conditions, it forms red prismatic crystals. {{chem2|PBr7}} can be prepared by the sublimation of a mixture of phosphorus pentabromide and bromine.{{Cite web |url=http://www.ebooksread.com/authors-eng/t-e-thomas-edward-thorpe/a-dictionary-of-applied-chemistry-volume-4-hci/1-a-dictionary-of-applied-chemistry-volume-4-hci.shtml |title=T. E. (Thomas Edward) Thorpe. A dictionary of applied chemistry (Volume 4) |access-date=2011-08-06 |archive-date=2019-04-10 |archive-url=https://web.archive.org/web/20190410003805/http://www.ebooksread.com/authors-eng/t-e-thomas-edward-thorpe/a-dictionary-of-applied-chemistry-volume-4-hci/1-a-dictionary-of-applied-chemistry-volume-4-hci.shtml |url-status=dead }}

:{{chem2|PBr5 + Br2 → PBr7}}

The structure of {{chem2|PBr7}} consists of a tetrabromophosphonium cation {{chem2|[PBr4]+}}, paired with a tribromide anion {{chem2|[Br3]–}}, and the tribromide anion is non-symmetric.{{cite journal | doi = 10.1107/S0365110X67002981 | title = The crystal structure of phosphorus heptabromide, PBr7 | year = 1967 | last1 = Breneman | first1 = G. L. | last2 = Willett | first2 = R. D. | journal = Acta Crystallographica | volume = 23 | issue = 3 | pages = 467–471| bibcode = 1967AcCry..23..467B }}