(Methylcyclopentadienyl)mangantricarbonyl

2008-03-08T14:44:43Z

Axiosaurus: corrected IUPAC name

{{Chembox new
| ImageFile = MMT-2D-skeletal.png
| ImageSize = 130px
| ImageFile1 = MMT-3D-balls.png
| ImageSize1 = 150px
| IUPACName = tricarbonyl(methyl-η5- cyclopentadienyl)manganese
| OtherNames = MMT
| Section1 = {{Chembox Identifiers
| SMILES =
| CASNo = 12108-13-3
| RTECS = OP1450000
}}
| Section2 = {{Chembox Properties
| Formula = C9H7MnO3
| MolarMass = 218.09 g/mol
| Appearance = pale yellow liquid herbaceous odor
| Density = 1.38 g/cm³
| Solubility = low
| Solvent = other solvents
| SolubleOther = [[alkane]] (petrol)
| MeltingPt = -1 °C (? K)
| BoilingPt = 232-233 °C
| Viscosity =
}}
| Section3 = {{Chembox Structure
| Coordination = Tetrahedral at Mn
| CrystalStruct = 
| Dipole =
}}
| Section7 = {{Chembox Hazards
| MainHazards = flammable
| FlashPt = 205 °F
| RPhrases = 23/24/25-40
| SPhrases = 23-26-36/37/39-45
}}
| Section8 = {{Chembox Related
| OtherCpds = [[ferrocene]] [[dimanganese decacarbonyl|Mn2(CO)10]] [[dicyclopentadiene]]
}}
}}

'''Methylcyclopentadienyl manganese tricarbonyl (MMT)''' is an [[organometallic compound]] with the formula (CH3C5H4)Mn(CO)3. Marketed initially in 1958 as a supplement to the [[gasoline additive]], [[tetraethyl lead]] to increase the fuel's [[octane rating]], MMT was later used in unleaded gasoline.<ref name="MMTHistoryatAfton">http://www.aftonchemical.com/Products/MMT/History+of+MMT®.htm</ref> Although banned as a gasoline additive in the United States from 1977 to 1995, MMT has been used in Canadian gasoline since 1976 and was recently introduced in [[Australia]]. It is sold under the tradenames HiTec 3000 and AK-33X.<ref name=Frumkin>Frumkin, Howard and Solomon, Gena; "Manganese in the US Gas Supply" American Journal of Industrial Medicine, 31: 107-115 (1997)</ref> It is also marketed as Ecotane® by [[T2 Labs]].<ref name=t2labs>{{cite web | url=http://www.t2labs.com/ecotane/ecotane.htm | title=T2 Labs is the manufacturer of Ecotane® | accessdate=December 20 | accessyear=2007 }}</ref>

==History==
Tetraethyl lead (TEL) has been, and still is, used as an additive to increase the octane rating of gasoline. TEL was manufactured and marketed by the [[Ethyl Corporation]], a joint venture between [[General Motors]] and [[DuPont]]. When the US [[United States Environmental Protection Agency|Environmental Protection Agency]] (EPA) ordered the phase out of leaded gasoline in 1972, new fuel additives were sought. Initially marketed in 1958 as a smoke suppressant for [[gas turbine]]s, MMT was used in 1974 as an additive in unleaded gasoline.

In 1977, use of MMT was banned in the US by the Clean Air Act until the Ethyl Corporation could prove that the additive would not lead to failure of new car emissions-control systems. As a result of this ruling, the Ethyl Corporation began a legal battle with the EPA, presenting evidence that MMT was harmless to automobile emissions-control systems. In 1995, the U.S. Court of Appeals ruled that the EPA had exceeded its authority and, as a result, MMT became a legal fuel additive in the US.<ref name=Kitazawa>Masashi Kitazawa, Jarrad R. Wagner, Michael L. Kirby, Vellareddy Anantharam, and Anumantha G. Kanthasamy; ''Oxidative Stress and Mitochondrial-Mediated Apoptosis in Dopaminergic Cells Exposed to Methylcyclopentadienyl Manganese Tricarbonyl'' J. Pharmacol. Exp. Ther., Jul 2002; 302: 26 - 35.</ref> MMT is nowadays manufactured by the Afton Chemical Corporation division of Newmarket Corporation.<ref name="MMTHistoryatAfton"/>

==Structure and bonding==
The compound is called a half-[[sandwich compound]]. The manganese atom in MMT is bonded to three carbonyl groups as well as to the [[methylcyclopentadiene|methylcyclopentadienyl]] ring. These hydrophobic organic ligands make MMT highly lipophilic, which may be relevant to bioacculumation. A variety of related complexes are known, including [[ferrocene]], which is also under consideration as an additive to gasoline.

==Preparation==
[[Image:MMT synthesis.svg|480px]]<ref name=MMTPatent>{{US patent|4946975}}</ref>

==Safety==
The health hazards associated with MMT have been hotly debated for decades. A 2003 study by the NICNAS in Australia suggested that MMT was highly toxic to humans in raw concentrated form, but ruled that the airborne concentrations of manganese as a result of car emissions from vehicles using fuel containing MMT posed no health hazard.<ref name=NINCAS>National Industrial Chemicals Notification and Assessment Scheme; ''Methylcyclopentadienyl Manganese Tricarbonyl'' June 2003. [http://www.nicnas.gov.au/PUBLICATIONS/CAR/PEC/PEC24/PEC_24_Full_Report_PDF.pdf]</ref> A 2002 study by Masashi Kitazawa argued that dermal absorption from accidental gasoline spills, misuse of gasoline as a solvent cleaner, and deliberate [[Inhalant|gasoline fume inhalation]] were the main sources of potential MMT exposure.

Chronic exposure to manganese has been known to cause [[manganism]]. The symptoms of manganism are similar to those of [[Parkinson's disease]]. MMT has been shown to be [[cytotoxic]] and especially damaging to dopaminergic PC-12 cells.<ref name=Kitazawa/> [[Toxicokinetic]] studies have shown that manganese derived from MMT absorbs into rat blood plasma at a rate 37 times that of inorganic manganese.<ref name=Zheng>Zheng W, Kim H and Zhao Q (2000) ''Comparative toxicokinetics of manganese chloride and methylcyclopentadienyl manganese tricarbonyl (MMT) in Sprague-Dawley rats.'' Toxicol Sci 54: 295-301.</ref>

Immediate symptoms of MMT exposure are mild skin and eye irritation. Short-term symptoms resulting from MMT poisoning include giddiness, headache, neausea, and difficulties in breathing. Animal studies have shown that long-term exposure to MMT can result in damage to the liver and kidneys.<ref name=WorldHealth>United Nations Environment Programme with the [[World Health Organization]]; ''Manganese''; Geneva, 1981.</ref>

A [[Jacksonville, Florida]] facility owned by [[T2 Labs]] that manufactured MMT under the trade name Ecotane® was destroyed by an explosion on December 19th, 2007. The blast, which sounded like a "gunshot" according to one witness and produced thick black smoke, killed four people and injured fourteen others.<ref name=cnn>{{cite web | url=http://www.cnn.com/2007/US/12/19/florida.explosion/index.html | title=Four dead in chemical plant explosion, officials say | accessdate=December 20 | accessyear=2007 }}</ref>

==References==
{{reflist}}

[[Category:Organometallic compounds]]
[[Category:manganese compounds]]
[[Category:Carbonyl complexes]]
[[Category:Antiknock agents]]

Paulingsche Verknüpfungsregeln

2007-12-20T09:24:44Z

Axiosaurus: added reference and content

'''Pauling's rules''' are five rules published by [[Linus Pauling]] in 1929<ref>{{cite journal
|last= |first= |authorlink= Pauling L |coauthors= |year= 1929|month= |title= The principles determining the structure of complex ionic crystals |journal= J. Am. Chem. Soc.|volume= 51 |issue= 4 |pages= 1010 - 1026 |doi= 10.1021/ja01379a006 |id= |url= |accessdate= |quote= }}</ref> for determining the [[molecular structure]]s of complex [[crystal]]s.

1. A coordinated [[polyhedron]] of [[anion]]s is formed about each [[cation]], the cation-anion distance determined by the sum of [[Ion|ionic]] radii and the [[coordination number]] (C.N.) by the radius ratio.

{| class="wikitable"
|+ Examples of radius ratios and related polyhedra
! Radius ratio !! C.N.!! polyhedron
|-
| .225 || 4 ||[[tetrahedral molecular geometry|tetrahedron]]
|-
| .414 || 6 ||[[octahedral molecular geometry|octahedron]]
|-
| .592|| 7 ||capped octahedron
|-
| .645 || 8 ||square antiprism (anti cube)
|-
| .732 || 8 ||cube
|-
| .732 || 9 || tri-capped trigonal prism
|-
| 1.00|| 12|| cube octahedron
|}

2. An ionic structure will be stable to the extent that the sum of the strengths of the [[electrostatic bond]]s that reach an anion equal the [[electric charge|charge]] on that anion. ("The electrostatic valence rule".)

: i.e. A stable ionic structure must be arranged to preserve Local Electroneutrality.
This is expressed mathematically as:
:<math> \xi = \sum_{i} s_i </math>
:where <math> \xi </math> is the charge of the anion and the summation is over the adjacent cations. 
Some examples are:

{| class="wikitable"
|+ Cations with oxide O2<nowiki>−</nowiki> ion
! Cation !! Radius ratio|| CN || Electrostatic bond strength
|-
| Li+ || 0.34||4|| 0.25
|-
| Mg2+ || 0.47||6||0.33
|-
| Sc3+ ||0.60|| 6||0.5
|}

3. The sharing of edges and particularly faces by two anion polyhedra decreases the stability of an ionic structure.

:Effect is largest for cations with high charge and low C.N (especially when r+/r- approaches the lower limit of the polyhedral stability).

4. In a [[crystal]] containing different cations, those of high [[valency (chemistry)|valency]] and small coordination number tend not to share polyhedron elements with one another.

5. The number of essentially different kinds of constituents in a crystal tends to be small.("The rule of parsimony".)

:Similar environments for chemically similar atoms.
==References==
<references/>

[[Category:Molecular geometry]]

[[fr:Règles de Pauling]]
[[ru:Правила Полинга]]

Wikipedia - Benutzerbeiträge [de]

(Methylcyclopentadienyl)mangantricarbonyl

Paulingsche Verknüpfungsregeln