Editing Manganese (section)

==Chemical compounds==
[[File:Chlorid manganatý.JPG|thumb|left|upright|[[Manganese(II) chloride]] crystals – the pale pink color of Mn(II) salts is due to a [[Spin-forbidden reactions|spin-forbidden]] 3d transition.<ref>{{cite book|title=Shriver and Atkins' Inorganic Chemistry|date=2010|publisher=Oxford University Press|isbn=978-0-19-923617-6|chapter=Ch. 20}}</ref>]]

Common [[oxidation state]]s of manganese are +2, +3, +4, +6, and +7, although all oxidation states from −3 to +7 have been observed. Manganese in oxidation state +7 is represented by salts of the intensely purple permanganate anion {{Chem2|MnO4-}}.{{sfn|Greenwood|Earnshaw|1997|pages=1042–1046}} [[Potassium permanganate]] is a commonly used laboratory [[reagent]] because of its oxidizing properties; it is used as a topical medicine (for example, in the treatment of fish diseases). Solutions of potassium permanganate were among the first stains and fixatives to be used in the preparation of biological cells and tissues for electron microscopy.<ref>{{cite journal |doi=10.1083/jcb.2.6.799 |last=Luft |first=J. H.|date=1956 |title=Permanganate – a new fixative for electron microscopy |journal=Journal of Biophysical and Biochemical Cytology |volume=2 |pages=799–802 |pmid=13398447 |issue=6 |pmc=2224005}}</ref>

Aside from various permanganate salts, Mn(VII) is represented by the unstable, volatile derivative Mn<sub>2</sub>O<sub>7</sub>. [[Oxyhalide]]s (MnO<sub>3</sub>F and MnO<sub>3</sub>Cl) are powerful [[oxidation|oxidizing agents]].<ref name="Holl" />  The most prominent example of Mn in the +6 oxidation state is the green anion [[manganate]], [MnO<sub>4</sub>]<sup>2−</sup>.  Manganate salts are intermediates in the extraction of manganese from its ores.  Compounds with oxidation states +5 are somewhat elusive, and often found associated to an oxide (O<sup>2−</sup>) or [[nitride]] (N<sup>3−</sup>) ligand.<ref>{{Unbulleted list citebundle|{{cite journal |doi=10.1021/ar400147y|title=Reactivity of Nitrido Complexes of Ruthenium(VI), Osmium(VI), and Manganese(V) Bearing Schiff Base and Simple Anionic Ligands |year=2014 |last1=Man |first1=Wai-Lun |last2=Lam |first2=William W. Y. |last3=Lau |first3=Tai-Chu |journal=Accounts of Chemical Research |volume=47 |issue=2 |pages=427–439 |pmid=24047467 }}|{{cite journal |doi=10.1021/ar700039y|title=Corrolazines: New Frontiers in High-Valent Metalloporphyrinoid Stability and Reactivity |year=2007 |last1=Goldberg |first1=David P. |journal=Accounts of Chemical Research |volume=40 |issue=7 |pages=626–634 |pmid=17580977 }}}}</ref>  One example is the blue anion [[hypomanganate]] [MnO<sub>4</sub>]<sup>3−</sup>.{{sfn|Greenwood|Earnshaw|1997|pages=1049–1051}}

Mn(IV) is somewhat enigmatic because it is common in nature but far rarer in synthetic chemistry. The most common Mn ore, [[pyrolusite]], is MnO<sub>2</sub>. It is the dark brown pigment of many [[cave drawing]]s<ref>{{cite journal | doi=10.1038/srep22159 | title=Selection and Use of Manganese Dioxide by Neanderthals | year=2016 | last1=Heyes | first1=Peter J. | last2=Anastasakis | first2=Konstantinos | last3=De Jong | first3=Wiebren | last4=Van Hoesel | first4=Annelies | last5=Roebroeks | first5=Wil | last6=Soressi | first6=Marie | journal=Scientific Reports | volume=6 | page=22159 | pmid=26922901 | pmc=4770591 | bibcode=2016NatSR...622159H }}</ref> and is also a common ingredient in [[dry cell]] batteries.{{sfn|Greenwood|Earnshaw|1997|pages=1048}} Complexes of Mn(IV), such as in [[manganese(IV) fluoride#Fluoromanganate(IV) complexes|K<sub>2</sub>[MnF<sub>6</sub>]]], are known but are rarer than those of manganese in the lower oxidation states. Mn(IV)-OH complexes are an intermediate in some [[enzyme]]s, including the oxygen-evolving center (OEC) in plants.{{sfn|Greenwood|Earnshaw|1997|pages=1056}}<ref>{{cite journal |doi=10.1021/cr4004874|title=Mn4Ca Cluster in Photosynthesis: Where and How Water is Oxidized to Dioxygen |year=2014 |last1=Yano |first1=Junko |last2=Yachandra |first2=Vittal |journal=Chemical Reviews |volume=114 |issue=8 |pages=4175–4205 |pmid=24684576 |pmc=4002066 }}</ref>

Simple derivatives of Mn<sup>3+</sup> are rarely encountered but can be stabilized by suitably [[alkaline]] ligands.  [[Manganese(III) acetate]] is an oxidant useful in [[organic synthesis]]. Solid compounds of manganese(III) are characterized by a strong purple-red color and a preference for distorted [[octahedral coordination]] resulting from the [[Jahn-Teller effect]].<ref>{{Cite journal|journal=Struct Chem |date=2017 |volume=28 |pages=201–212 |doi=10.1007/s11224-016-0864-0 |title=An historic and scientific study of the properties of metal(III) tris-acetylacetonates |first1=Evrim |last1=Arslan |first2=Roger A. |last2=Lalancette |first3=Ivan |last3=Bernal|issue=1 |bibcode=2017StrCh..28..201A }}</ref> [[File:KMnO4 in H2O.jpg|thumb|left|upright=0.55|Aqueous solution of KMnO<sub>4</sub> illustrating the deep purple of Mn(VII) as it occurs in permanganate]]
A particularly common oxidation state for manganese in aqueous solution is +2, which has a pale pink color. Many manganese(II) compounds are known, such as the [[aquo complex]]es derived from [[manganese(II) sulfate]] (MnSO<sub>4</sub>) and [[manganese(II) chloride]] (MnCl<sub>2</sub>). This oxidation state is also seen in the mineral [[rhodochrosite]] ([[manganese(II) carbonate]]). Manganese(II) commonly exists with a [[Spin states (d electrons)|high-spin]] ground state, with 5 unpaired electrons, because of its high pairing energy. There are no spin-allowed d–d transitions in manganese(II), which explain its faint color.<ref>{{Cite book|last1=Rayner-Canham |first1=Geoffrey |last2=Overton |first2=Tina |date=2003 |title=Descriptive Inorganic Chemistry |publisher=Macmillan |page=491 |isbn=0-7167-4620-4}}.</ref>
{| class="wikitable floatright"
|-
! colspan=2|Oxidation states of manganese<ref name="Schmidt">{{cite book|title=Anorganische Chemie II.|chapter=VII. Nebengruppe |pages=100–109|first=Max|last=Schmidt|publisher=Wissenschaftsverlag|date=1968|language=de}}</ref>
|-
| −3 || {{chem|Mn(CO)(NO)|3|}}
|-
| −2 || [Mn([[1,5-cyclooctadiene|1,5-COD]])<sub>2</sub>]<sup>2−</sup>
|-
| −1 || [[Pentacarbonylhydridomanganese|{{chem|H|Mn|(CO)|5}}]]
|-
| 0 || [[Dimanganese decacarbonyl|{{chem|Mn|2|(CO)|10}}]]
|-
| +1 || [[Methylcyclopentadienyl manganese tricarbonyl|{{chem|MnC|5|H|4|CH|3|(CO)|3}}]]
|-
| '''+2''' || [[Manganese(II) chloride|{{chem|MnCl|2}}]], [[Manganese(II) carbonate|{{chem|MnCO|3}}]], [[Manganese(II) oxide|{{chem|MnO}}]]
|-
| +3 || [[Manganese(III) fluoride|{{chem|MnF|3}}]], [[Manganese(III) acetate|{{chem|Mn(OAc)|3}}]], [[Manganese(III) oxide|{{chem|Mn|2|O|3}}]]
|-
| '''+4''' || [[Manganese dioxide|{{chem|MnO|2}}]]
|-
| +5 || [[Potassium hypomanganate|{{chem|K|3|MnO|4}}]]
|-
| +6 || [[Potassium manganate|{{chem|K|2|MnO|4}}]]
|-
| '''+7''' || [[Potassium permanganate|{{chem|KMnO|4}}]], [[Manganese heptoxide|{{chem|Mn|2|O|7}}]]
|-
|colspan=2 style="font-size: smaller; text-align: center"|Common oxidation states are in bold.
|}

===Organomanganese compounds===
{{main|Organomanganese chemistry}}
Manganese forms a large variety of organometallic derivatives, i.e., compounds with Mn-C bonds. The organometallic derivatives include numerous examples of Mn in its lower oxidation states, i.e. Mn(−III) up through Mn(I). This area of organometallic chemistry is attractive because Mn is inexpensive and of relatively low toxicity.<ref>{{cite journal |doi=10.1021/acs.inorgchem.9b00941 |title=Resurgence of Organomanganese(I) Chemistry. Bidentate Manganese(I) Phosphine–Phenol(ate) Complexes |date=2019 |last1=Kadassery |first1=Karthika J. |last2=MacMillan |first2=Samantha N. |last3=Lacy |first3=David C. |journal=Inorganic Chemistry |volume=58 |issue=16 |pages=10527–10535 |pmid=31247867 }}</ref>

Of greatest commercial interest is [[methylcyclopentadienyl manganese tricarbonyl]] (MMT), which is used as an [[anti-knock]] compound added to [[gasoline]] in some countries, featuring Mn(I).<ref name="ullmann" /> Consistent with other aspects of Mn(II) chemistry, [[manganocene]] ({{chem2|Mn(C5H5)2}}) is high-spin. In contrast, its neighboring metal, iron, forms an air-stable, low-spin derivative in the form of [[ferrocene]] ({{chem2|Fe(C5H5)2}}).  When conducted under an atmosphere of [[carbon monoxide]], reduction of Mn(II) salts gives [[dimanganese decacarbonyl]] {{chem2|Mn2(CO)10}}, an orange and volatile solid.  The air-stability of this Mn(0) compound (and its many derivatives) reflects the powerful electron-acceptor properties of carbon monoxide. Many [[alkene complex]]es and [[alkyne complex]]es are derived from {{chem2|Mn2(CO)10}}.{{sfn|Greenwood|Earnshaw|1997|pages=1062-1069}}

In Mn(CH<sub>3</sub>)<sub>2</sub>(dmpe)<sub>2</sub>, Mn(II) is low spin, which contrasts with the high spin character of its precursor, MnBr<sub>2</sub>(dmpe)<sub>2</sub> ([[dmpe]] =  (CH<sub>3</sub>)<sub>2</sub>PCH<sub>2</sub>CH<sub>2</sub>P(CH<sub>3</sub>)<sub>2</sub>).<ref>{{cite journal |doi=10.1021/ja00360a054|title=Hydrido, alkyl, and ethylene 1,2-bis(dimethylphosphino)ethane complexes of manganese and the crystal structures of MnBr2(dmpe)2, &#91;Mn(AlH4)(dmpe)2&#93;2 and MnMe2(dmpe)2 |year=1983 |last1=Girolami |first1=Gregory S. |last2=Wilkinson |first2=Geoffrey |last3=Thornton-Pett |first3=Mark |last4=Hursthouse |first4=Michael B. |journal=Journal of the American Chemical Society |volume=105 |issue=22 |pages=6752–6753 |bibcode=1983JAChS.105.6752G }}</ref> Poly[[Alkyl group|alkyl]] and poly[[Aryl group|aryl]] derivatives of manganese often exist in higher oxidation states, reflecting the electron-releasing properties of alkyl and aryl ligands.  One example is [Mn(CH<sub>3</sub>)<sub>6</sub>]<sup>2−</sup>.<ref>{{cite journal |author1=Robert J. Morris |author2=Gregory S. Girolami |title=Permethylmanganates. Synthesis and characterization of divalent [MnMe<sub>4</sub><sup>2-</sup>], trivalent [MnMe<sub>5</sub><sup>2-</sup>], and tetravalent [MnMe<sub>6</sub><sup>2-</sup>] |journal=Journal of the American Chemical Society |date=1988 |volume=110 |issue=18 |pages=6245–6246 |doi=10.1021/ja00226a049 |publisher=ACS Publications |pmid=22148809 |bibcode=1988JAChS.110.6245M |language=en}}</ref>