{{chembox | Verifiedfields = changed | verifiedrevid = 464210357 | ImageFile = Polythiazyl-2D-dimensions.png | ImageSize = 240px | ImageFile1 = (SN)x.png | ImageSize1 = 240px | ImageFile2 = Polythiazyl-chain-from-neutron-3D-vdW.png | ImageSize2 = 240px | IUPACName = | OtherNames = polythiazyl<br />poly(sulfur nitride) |Section1={{Chembox Identifiers | CASNo = 56422-03-8 | CASNo_Ref = {{cascite|changed|??}} | PubChem = | ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}} | ChemSpiderID = none | SMILES =}} |Section2={{Chembox Properties | Formula = {{chem2|(SN)_{''x''}|}} | MolarMass = | Appearance = Golden or bronze-coloured crystalline solid with metallic lustre<ref name="G&E">{{ Greenwood&Earnshaw | pages = 725–727}}</ref> | Density = | MeltingPt = | BoilingPt = | Solubility =}} |Section3={{Chembox Hazards | MainHazards = | FlashPt = | AutoignitionPt =}} }}
'''Polythiazyl''' (polymeric sulfur nitride), {{chem2|(SN)_{''x''}|}}, is an electrically conductive, gold- or bronze-colored polymer with metallic luster. It was the first conductive inorganic polymer discovered<ref name="G&E" /><ref name=":02">{{Cite journal|last1=Goehring|first1=Margot|last2=Voigt|first2=Dietrich|date=1953|title=Über die Schwefelnitride (SN)<sub>2</sub> und (SN)<sub>x</sub>|journal=Die Naturwissenschaften|language=de|volume=40|issue=18|pages=482|doi=10.1007/BF00628990|bibcode=1953NW.....40..482G|s2cid=8181710|issn=0028-1042}}</ref> and was also found to be a superconductor at very low temperatures (below 0.26 K).<ref>{{ cite journal | title = Polysulfur Nitride - a Metallic, Superconducting Polymer |author1=Labes, M. M. |author2=Love, P. |author3=Nichols, L. F. | journal = Chemical Reviews | year = 1979 | volume = 79 | issue = 1 | pages = 1–15 | doi = 10.1021/cr60317a002}}</ref><ref name="Allcock2011">{{cite book|author=Harry R. Allcock|title=Introduction to Materials Chemistry|url=https://books.google.com/books?id=CnnbJG7f7dwC&pg=PT131|accessdate=29 June 2012|date=20 September 2011|publisher=John Wiley & Sons|isbn=978-1-118-21098-7|page=131}}</ref> It is a fibrous solid, described as "lustrous golden on the faces and dark blue-black", depending on the orientation of the sample. It is air stable and insoluble in all solvents.<ref>{{cite book |author1=A. G. MacDiarmid |author1-link=A. G. MacDiarmid |title=Inorganic Syntheses |author2=C. M. Mikulsk |author3=A. J. Heeger |author3-link=A. J. Heeger |author4=A. F. Garito |author-link4=A. F. Garito |year=1983 |isbn=9780470132531 |volume=22 |pages=143–149 |chapter=Polymeric Sulfur Nitride (Polythiazyl), (SN)<sub>''x''</sub> |doi=10.1002/9780470132531.ch31}}</ref>
==History== The compound was first reported as early as 1910 by F.P. Burt, who obtained it by heating tetrasulfur tetranitride in vacuum over silver wool.<ref>{{Cite journal|last=Burt|first=Frank Playfair|date=1910|title=XCIX.—A new sulphide of nitrogen|journal=J. Chem. Soc., Trans.|language=en|volume=97|pages=1171–1174|doi=10.1039/CT9109701171|issn=0368-1645|url=https://zenodo.org/record/2250224}}</ref>
The compound was the first compound with only non-metallic elements in which superconductivity could be demonstrated.<ref>{{cite journal | last1=Labes | first1=M. M. | last2=Love | first2=P. | last3=Nichols | first3=L. F. | title=Polysulfur nitride - a metallic, superconducting polymer | journal=Chemical Reviews | date=1979 | volume=79 | pages=1–15 | doi=10.1021/cr60317a002 }}</ref><ref name="Riedel">Klapötke, Thomas M.: "Nichtmetallchemie" [Chemistry of nonmetals] (in German). In ''Moderne Anorganische Chemie'' [''Modern Inorganic Chemistry''], E. Riedel (ed.), 3rd ed. (2007). Walter de Gruyter GmbH & Co. KG: Berlin/Boston, {{ISBN|978-3-11-019060-1}}, pp. 129–132 (via De Gruyter Online).</ref>
== Properties == Polythiazyl is a metallic-golden and shiny, crystalline but fibrous material with anisotropic electrical conductivity.<ref name="Riedel" /> It has at least two crystal polymorphs, which are usually intermixed after chemical synthesis. About 90% is the monoclinic form I, while the remainder is an orthorhombic form II.<ref name=King/>{{rp|10}} The orthorhombic portion can be increased mechanically through e.g. grinding,<ref name="Baughman">{{cite journal | last1=Baughman | first1=R. H. | last2=Apgar | first2=P. A. | last3=Chance | first3=R. R. | last4=MacDiarmid | first4=A. G. | last5=Garito | first5=A. F. | title=A new phase of (SN)<sub>x</sub> | journal=Journal of the Chemical Society, Chemical Communications | date=1977 | issue=2 | page=49 | doi=10.1039/C39770000049 }}</ref> "although full conversion is unlikely."<ref name=King/>{{Rp|10}}
Along the fibres (SN chains), polythiazyl is electrically conductive; perpendicular, an insulator. The one-dimensional conductivity arises from bonding conditions in the S-N chain, where each sulfur atom provides two π electrons and each nitrogen atom provides one π electron to form two-center 3π electron bonding units.<ref name=Riedel/> At temperatures below 0.3 K, it becomes a electrical superconductor.<ref name="Riedel" /> The Peierls distortion is inhibited by weak inter-chain interactions, which resist the characteristic bond alternation.<ref name=King>King, R.S.P.: ''[https://dspace.lboro.ac.uk/dspace-jspui/handle/2134/12571 Novel chemistry and applications of polythiazyl]'' (Doctoral Thesis). From Loughborough University, 2009</ref>{{rp|pp=12-13}}
Polythiazyl is "completely insoluble";<ref name=King/>{{rp|13}} and mostly inert to oxygen and water.<ref name="MacDiarmid"/><ref name=Roempp>{{RömppOnline|Name=Schwefel-Stickstoff-Verbindungen |Datum=2 March 2017 |ID=RD-19-01408}}</ref> But it decomposes rapidly in alkaline solutions,<ref name=King/>{{rp|13}} and slowly in air to a grey powder after months of exposure.<ref name="MacDiarmid"/><ref name=Roempp/> Halogens intercalate between the strands.<ref name=King/>{{Rp|pp=15-16}}
At temperatures above 240 °C explosive decomposition can occur.<ref name="Holleman-Wiberg2017">Wiberg, E.; Wiberg, N.; Holleman, A.F.: ''Anorganische Chemie'' (in German), 103rd printing (2017) by Walter de Gruyter GmbH & Co. KG, Berlin/Boston, {{ISBN|978-3-11-026932-1}}, p. 681, (retrieved via De Gruyter Online).</ref> The compound also explodes on impact.<ref name="Roempp" /> Explosion generally proceeds via decomposition to the elements.
Vapor sublimed from polythiazyl is actually a cracked form of the polymer, the six-membered radical ring (SN)<sub>3</sub>. Condensation reverts it back to the chain form.<ref>{{cite book|p=305|title=Progress in Inorganic Chemistry|editor-first=Stephen L.|editor-last=Lippard|volume=36|publisher=Interscience|location=NY, NY|lccn=59-13035|isbn=0-471-61144-1|chapter=Cyclic and heterocyclic thiazines|first=Richard T.|last=Oakley}}</ref>
===Molecular structure and bonding=== The material is a polymer, containing trivalent nitrogen and divalent and tetravalent sulfur. The S and N atoms on adjacent chains align.<ref name=":02" /><ref>{{Cite journal|last=Goehring|first=Margot|date=1956|title=Sulphur nitride and its derivatives|journal=Quarterly Reviews, Chemical Society|language=en|volume=10|issue=4|pages=437|doi=10.1039/qr9561000437|issn=0009-2681}}</ref><ref>{{cite journal|title=Solid state polymerization of S<sub>2</sub>N<sub>2</sub> to (SN)<sub>x</sub>|author1=Cohen, M.J .|author2=Garito, A. F.|author3=Heeger, A. J.|author4=MacDiarmid, A. G.|author5=Mikulski, C. M.|author6=Saran, M. S.|author7=Kleppinger, J. |journal=Journal of the American Chemical Society|year=1976|volume=98|pages=3844–3848|doi=10.1021/ja00429a018}}</ref> Several resonance structures can be written.<ref>{{ cite journal | title = Examination of Electronic Phase of the Hartree-Fock Solution of an Isolated Polythiazyl Chain |author1=Okada, M. |author2=Tanaka, K. |author3=Takata, A. |author4=Yamabe, T. | journal = Synthetic Metals | volume = 59 | issue = 2 | year = 1993 | pages = 223–230 | doi = 10.1016/0379-6779(93)91029-2}}</ref> :Polythiazyl resonance structures|upright=3.5|class=skin-invert-image The structure of the crystalline compound was resolved by X-ray diffraction. This showed alternating S–N bond lengths of 159 pm and 163 pm and S–N–S bond angles of 120 ° and N–S–N bond angles of 106 °.<ref>{{cite journal |last=Boudeulle |first=M. |year=1975 |title=Beta poly-(sulfur nitride), (SN)<sub>x</sub> |journal=Crystal Structure Communications |volume=4 |pages=9–13}}</ref><ref>{{cite journal | last1=MacDiarmid | first1=Alan G. | last2=Mikulski | first2=Chester M. | last3=Russo | first3=Peter J. | last4=Saran | first4=Mohan S. | last5=Garito | first5=Anthony F. | last6=Heeger | first6=Alan J. | title=Synthesis and structure of the polymeric metal, (SN)<sub>x</sub> , and its precursor, S<sub>2</sub>N<sub>2</sub> | journal=Journal of the Chemical Society, Chemical Communications | date=1975 | issue=12 | page=476 | doi=10.1039/C39750000476 }}</ref><ref name="MacDiarmid">{{cite book | last1=MacDiarmid | first1=A. G. | last2=Mikulski | first2=C. M. | last3=Saran | first3=M. S. | last4=Russo | first4=P. J. | last5=Cohen | first5=M. J. | last6=Bright | first6=A. A. | last7=Garito | first7=A. F. | last8=Heeger | first8=A. J. | title=Inorganic Compounds with Unusual Properties | chapter=Synthesis and Selected Properties of Polymeric Sulfur Nitride, (Polythiazyl), (SN)<sub>x</sub> | series=Advances in Chemistry | date=1976 | volume=150 | pages=63–72 | doi=10.1021/ba-1976-0150.ch006 | isbn=978-0-8412-0281-8 }}</ref><ref name="Riedel" />
==Synthesis== The oldest-known polythiazyl synthesis is the polymerization of the cyclic formal dimer disulfur dinitride ({{chem2|S2N2}}), which is in turn synthesized from the formal tetramer tetrasulfur tetranitride ({{chem2|S4N4}}),<ref name=":02" /> in the presence of hot silver wool.<ref name=":02" /><ref name="G&E" /><ref name="Archer2001" /> The reaction begins when silver abstracts sulfur from {{chem2|S4N4}} to produce a {{chem2|Ag2S}} catalyst; the resulting gaseous {{chem2|S2N2}} is then isolated through sublimation onto a cold surface: :S<sub>4</sub>N<sub>4</sub> + 8 Ag → 4 Ag<sub>2</sub>S + 2 N<sub>2</sub> :S<sub>4</sub>N<sub>4</sub> (low-pressure gas at 250-300 °C; Ag<sub>2</sub>S catalyst) → 2 S<sub>2</sub>N<sub>2</sub> (gas) → 2 S<sub>2</sub>N<sub>2</sub> (stable solid at 77 K) When warmed to room temperature, the additional heat induces impurity-catalyzed polymerization:<ref name=Oakley>{{cite book|p=304|title=Progress in Inorganic Chemistry|editor-first=Stephen L.|editor-last=Lippard|volume=36|publisher=Interscience|location=NY, NY|lccn=59-13035|isbn=0-471-61144-1|chapter=Cyclic and heterocyclic thiazines|first=Richard T.|last=Oakley}}</ref> :S<sub>2</sub>N<sub>2</sub> (0 °C) → (SN)<sub>x</sub>
An alternative is the azide reduction of thiazyl chloride trimer,<ref name=Radicals>{{cite book|page=322|title=Stable Radicals|editor-first=Robin G.|editor-last=Hicks|publisher=Wiley|year=2010|isbn=978-0-470-77083-2|chapter=The synthesis and characterization of stable radicals containing the thiazyl (SN) fragment and their use as building blocks for advanced functional materials|first=Robin G.|last=Hicks}}</ref> itself made from thiazyl fluoride:<ref name=Sulf>{{cite book|title=Sulfur in Organic and Inorganic Chemistry|volume=1|editor-first=Alexander|editor-last=Senning|year=1971|publisher=Marcel Dekker|location=New York|lccn=70-154612|isbn=0-8247-1615-9|first=H. W.|last=Roesky|chapter=The Sulfur–Nitrogen Bond|pages=20–23}}</ref> :(NSF)<sub>3</sub> + Cl<sub>2</sub> → (SNCl)<sub>3</sub> + ClF :(SNCl)<sub>3</sub> + NaN<sub>3</sub> → NaCl + N<sub>2</sub> + (SN)<sub>∞</sub> To eschew explosive reagents entirely, iron filings in nitromethane reduce the thiazyl chloride trimer to [(SN)<sub>5</sub>]<sup>+</sup>[FeCl<sub>4</sub>]<sup>−</sup>,<ref>{{cite journal|pages=1457–1460|title=Some reductions of sulphur-nitrogen-chloride compounds to give tetrasulphur tetranitride|first1=Arthur J.|last1=Banister|first2=Andrew J.|last2=Fielder|first3=Richard G.|last3=Hey|first4=Nigel R. M.|last4=Smith|journal= J. Chem. Soc., Dalton Trans.|orig-date=21 June 1979|year=1980|issue=8 |doi=10.1039/DT9800001457 }}</ref> which a platinum cathode reduces to polythiazyl.<ref>{{cite journal|pages=1016–1018|journal=Journal of the Chemical Society, Chemical Communications|year=1983|title=Electrochemical synthesis of poly(sulphur nitride)|first1=Arthur J.|last1=Banister|first2=Zdenek V.|last2=Hauptman|first3=Aidan G.|last3=Kendrick|issue=18 |doi=10.1039/c39830001016 |orig-date=1 June 1983}}</ref>
==Uses== Due to its electrical conductivity, polythiazyl is used in LEDs, transistors, battery cathodes, and solar cells.<ref name="Archer2001">{{cite book|author=Ronald D. Archer|title=Inorganic and Organometallic Polymers|url=https://books.google.com/books?id=9KFwwpv6bGcC&pg=PA213|accessdate=29 June 2012|date=26 February 2001|publisher=John Wiley & Sons|isbn=978-0-471-24187-4|page=213}}</ref>
==References== {{reflist}}
Category:Inorganic polymers Category:Nitrides Category:Superconductors Category:Sulfur–nitrogen compounds Category:Conductive polymers