Gold Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! === Rare oxidation states === Less common oxidation states of gold include β1, +2, and +5. The β1 oxidation state occurs in aurides, compounds containing the {{chem2|Auβ}} [[anion]]. [[Caesium auride]] (CsAu), for example, crystallizes in the [[caesium chloride]] motif;<ref name="relativist_Au_Pt">{{Cite journal |title=Effects of relativistic motion of electrons on the chemistry of gold and platinum |first=Martin |last=Jansen |journal=Solid State Sciences |volume=7 |issue=12 |date=2005 |doi=10.1016/j.solidstatesciences.2005.06.015 |pages=1464β1474 |bibcode=2005SSSci...7.1464J|doi-access=free}}</ref> rubidium, potassium, and [[tetramethylammonium]] aurides are also known.<ref name="Holleman">{{cite book |last1=Holleman |first1=A. F. |last2=Wiberg |first2=E. |title=Inorganic Chemistry |publisher=Academic Press |location=San Diego |year=2001 |isbn=978-0-12-352651-9}}</ref> Gold has the highest [[electron affinity]] of any metal, at 222.8 kJ/mol, making {{chem2|Auβ}} a stable species,<ref name="martin08">{{cite journal |last=Jansen |first=Martin |title=The chemistry of gold as an anion |journal=Chemical Society Reviews |date=2008 |volume=37 |issue=9 |pages=1826β1835 |doi=10.1039/b708844m |pmid=18762832}}</ref> analogous to the [[halide]]s. Gold also has a β1 oxidation state in covalent complexes with the [[Group 4 element|group 4]] transition metals, such as in titanium tetraauride and the analogous zirconium and hafnium compounds. These chemicals are expected to form gold-bridged [[dimer (chemistry)|dimer]]s in a manner similar to [[titanium(IV) hydride]].<ref>{{cite journal |title= Gold Behaves as Hydrogen in the Intermolecular Self-Interaction of Metal Aurides MAu<sub>4</sub> (M=Ti, Zr, and Hf) |first1= Jaehoon |last1= Jung |first2= Hyemi |last2= Kim |first3= Jong Chan |last3= Kim |first4= Min Hee |last4= Park |first5= Young-Kyu |last5= Han |journal= Chemistry: An Asian Journal |volume= 6 |issue= 3 |year= 2011 |pages= 868β872 |doi= 10.1002/asia.201000742 |pmid= 21225974 }}</ref> Gold(II) compounds are usually [[diamagnetic]] with AuβAu bonds such as [{{chem2|Au(CH2)2P(C6H5)2]2Cl2}}. The evaporation of a solution of {{chem2|Au(OH)3}} in concentrated {{chem2|H2SO4}} produces red crystals of [[gold(II) sulfate]], {{chem2|Au2(SO4)2}}. Originally thought to be a mixed-valence compound, it has been shown to contain {{chem2|Au2(4+)}} cations, analogous to the better-known [[mercury(I)]] ion, {{chem2|Hg2(2+)}}.<ref>{{Cite journal |last=Wickleder |first=Mathias S. |doi=10.1002/1521-3749(200109)627:9<2112::AID-ZAAC2112>3.0.CO;2-2 |date=2001 |title=AuSO<sub>4</sub>: A True Gold(II) Sulfate with an Au<sub>2</sub><sup>4+</sup> Ion |journal=Journal of Inorganic and General Chemistry |volume=627 |pages=2112β2114 |issue=9}}</ref><ref>{{Cite book |last=Wickleder |first=Mathias S. |title=Handbook of chalcogen chemistry: new perspectives in sulfur, selenium and tellurium |editor-first=Francesco A. |editor-last=Devillanova |publisher=Royal Society of Chemistry |date=2007 |isbn=978-0-85404-366-8 |pages=359β361 |url=https://books.google.com/books?id=IvGnUAaSqOsC&pg=PA359}}</ref> A gold(II) complex, the [[tetraxenonogold(II)]] cation, which contains [[xenon]] as a ligand, occurs in {{chem2|[AuXe4](Sb2F11)2}}.<ref>{{Cite journal |last1=Seidel |first1=S. |last2=Seppelt |first2=K. |title=Xenon as a Complex Ligand: The Tetra Xenono Gold(II) Cation in AuXe<sub>4</sub><sup>2+</sup>(Sb<sub>2</sub>F<sub>11</sub><sup>β</sup>)<sub>2</sub> |journal=Science |date=2000 |volume=290 |issue=5489 |pages=117β118 |doi=10.1126/science.290.5489.117 |pmid=11021792 |bibcode=2000Sci...290..117S}}</ref> In September 2023, a novel type of [[Perovskite (structure)|metal-halide perovskite material]] consisting of Au<sup>3+</sup> and Au<sup>2+</sup> cations in its crystal structure has been found.<ref>{{Cite web |last=University |first=Stanford |title=Striking rare gold: Researchers unveil new material infused with gold in an exotic chemical state |url=https://phys.org/news/2023-09-rare-gold-unveil-material-infused.html |access-date=2 October 2023 |website=phys.org |language=en}}</ref> It has been shown to be unexpectedly stable at normal conditions. [[Gold pentafluoride]], along with its derivative anion, {{chem2|AuF6-}}, and its [[difluorine complex]], [[gold heptafluoride]], is the sole example of gold(V), the highest verified oxidation state.<ref>{{Cite journal |last1=Riedel |first1=S. |last2=Kaupp |first2=M. |title=Revising the Highest Oxidation States of the 5d Elements: The Case of Iridium(+VII) |journal=Angewandte Chemie International Edition |date=2006 |volume=45 |issue=22 |pmid=16639770 |pages=3708β3711 |doi=10.1002/anie.200600274}}</ref> Some gold compounds exhibit ''[[aurophilicity|aurophilic bonding]]'', which describes the tendency of gold ions to interact at distances that are too long to be a conventional AuβAu bond but shorter than [[Van der Waals force|van der Waals bonding]]. The interaction is estimated to be comparable in strength to that of a [[hydrogen bond]]. Well-defined cluster compounds are numerous.<ref name="Holleman" /> In some cases, gold has a fractional oxidation state. A representative example is the octahedral species {{chem2|{Au([[triphenylphosphine|P(C6H5)3]])}6(2+)}}. Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here. You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see Christianpedia:Copyrights for details). Do not submit copyrighted work without permission! Cancel Editing help (opens in new window) Discuss this page