(Methylcyclopentadienyl) manganese tricarbonyl
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| Surname | (Methylcyclopentadienyl) manganese tricarbonyl | |||||||||||||||
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| Molecular formula | C 9 H 7 MnO 3 | |||||||||||||||
| Brief description |
dark orange liquid with a pleasant odor |
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| properties | ||||||||||||||||
| Molar mass | 218.09 g mol −1 | |||||||||||||||
| Physical state |
liquid |
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| density |
1.39 g cm −3 |
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| Melting point |
2.2 ° C |
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| boiling point |
232.8 ° C |
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| Vapor pressure |
0.063 mbar (20 ° C) |
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| solubility |
very heavy in water (10 mg l −1 at 20 ° C) |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | ||||||||||||||||
(Methylcyclopentadienyl) manganese tricarbonyl (abbr .: MMT or MCMT ) is an organometallic half-sandwich complex of manganese with the half-structural formula [(CH 3 C 5 H 4 ) Mn (CO) 3 ]. It is a dark orange liquid with a faint, pleasant odor. The compound was used from 1958 as an additive to the additive tetraethyl lead , later it was used in unleaded fuel. The purpose was to increase the octane number .
Although MMT was banned as a gasoline additive in the US from 1977 to 1995, it was used in Canada from 1976. Between 1997 and 1998 it was no longer used due to health risks.
MMT is sold under the trade names HiTec 3000 and AK-33X . It is marketed by T2 Labs under the name Ecotane .
history
Tetraethyl lead (TEL) is selected as an additive for older gasoline engines in order to reduce knocking by increasing the octane number. TEL was manufactured and sold by Ethyl Corporation (a joint venture between General Motors and DuPont ). When the US Environmental Protection Agency (EPA) ordered the phasing out of fuel lead in 1972, ethyl was looking for alternatives. One of them was MMT, which was used from 1958 as a smoke suppressor in gas turbines and from 1974 as an additive in unleaded petrol.
In 1977 the use of MMT as an additive was banned in the USA by the Clean Air Act until the manufacturer Ethyl provided evidence that the additive did not lead to the failure of the catalytic converters. As a result, a legal battle between Ethyl and EPA began, in which in 1995 the appellate court ruled that the EPA had exceeded its competences. This made MMT a legal petrol additive in the USA. MMT is currently being marketed by the ethyl successor Afton Chemical (part of NewMarket Corporation ) and by Cestoil Chemical Inc. in Canada (there under the name Cestoburn ).
In Germany, the use of (methylcyclopentadienyl) manganese tricarbonyl was prohibited by the lead gas law.
Manufacturing
The first step is the reaction between methylcyclopentadiene and sodium in diethylene glycol dimethyl ether . Sodium methylcyclopentadiene is formed with the release of hydrogen gas. By adding manganese (II) chloride , the sandwich complex manganese dimethylcyclopentadiene and sodium chloride is formed .
The reaction of manganese (II) acetate , triethylaluminum and carbon monoxide with the manganese dimethylcyclopentadiene produces (methylcyclopentadienyl) manganese tricarbonyl in the last step of the synthesis.
properties
(Methylcyclopentadienyl) manganese tricarbonyl is a dark orange, little volatile and hardly inflammable liquid with a pleasant odor, which is very sparingly soluble in water.
The connection is known as the half-sandwich or piano chair complex . The manganese atom in MMT is bound to three carbonyl groups and a methylcyclopentadienyl ring. These hydrophobic organic ligands make MMT highly lipophilic, which favors bioaccumulation .
safety instructions
The health risks associated with MMT have been heatedly and controversially discussed for decades. A study published in Australia in 2003 allows the conclusion that MMT in concentrated form is highly toxic to humans, but at the same time mentions that the manganese concentrations measured in the air as a result of car exhaust when using MMT did not pose a health risk. A study from 2002 (Kitazawa et al.) Indicated that skin absorption from accidental fuel spills, misuse of fuel as a solvent for degreasing, and (deliberate) inhalation of vapors are the main routes of potential MMT exposure.
Long-term exposure to manganese will develop symptoms of manganism that are similar to Parkinson's disease . A cytotoxic effect has also been demonstrated for MMT and, in particular, damage to dopaminergic PC-12 cells. Toxicokinetic studies have shown that manganese from MMT is absorbed into blood plasma of rats at 37 times the rate of inorganic manganese.
Immediate symptoms of contact with MMT are mild skin and eye irritation. Short-term symptoms associated with MMT poisoning include headache, vomiting, and difficulty breathing. Animal studies have shown that long-term exposure to MMT can result in liver and kidney damage.
The vapors of (methylcyclopentadienyl) manganese tricarbonyl can form an explosive mixture with air ( flash point 96 ° C).
Recommendations from automakers
Before using MMT, it is recommended to clarify whether the manufacturer recommends the use of MMT additives or not. General Motors, for example, explicitly advises against it.
literature
- RJ Minjares, M. Walsh, K. Blumberg: Methylcyclopentadienyl manganese tricarbonyl (MMT): a science and policy review. In: International Council on Clean Transportation , (2009).
Web links
- Curves showing relationships between metal concentration and achievable RON
- Manganese fuel lobby puts pressure on US government: car manufacturers should no longer decide on catalyst tests (PDF; 13 kB)
Individual evidence
- ↑ a b c d e f g h i j k l Entry on tricarbonyl (methylcyclopentadienyl) manganese in the GESTIS substance database of the IFA , accessed on January 9, 2019(JavaScript required) .
- ↑ David C. Dorman, Melvin E. Andersen, Jerry M. Roper and Michael D. Taylor: Update on a Pharmacokinetic-Centric Alternative Tier II Program for MMT — Part I: Program Implementation and Lessons Learned Journal of Toxicology 2012, Article ID 946742 , doi: 10.1155 / 2012/946742
- ^ Threat of NAFTA Case Kills Canada's MMT Ban . In: The Globe and Mail , July 20, 1998: Challenge over gasoline additive could have cost Ottawa millions .
- ^ H. Frumkin, G. Solomon: Manganese in the US gasoline supply. In: American journal of industrial medicine. Volume 31, Number 1, January 1997, pp. 107-115, PMID 8986262 .
- ↑ T2 Labs is the manufacturer of Ecotane . Retrieved December 20, 2007.
- ↑ a b M. Kitazawa, JR Wagner, ML Kirby, V. Anantharam, AG Kanthasamy: Oxidative stress and mitochondrial-mediated apoptosis in dopaminergic cells exposed to methylcyclopentadienyl manganese tricarbonyl. In: The Journal of pharmacology and experimental therapeutics. Volume 302, Number 1, July 2002, pp. 26-35, PMID 12065696 .
- ↑ Text of the Gasoline Lead Act
- ↑ National Industrial Chemicals Notification and Assessment Scheme: Methylcyclopentadienyl Manganese Tricarbonyl June 2003 ( Memento from March 3, 2016 in the Internet Archive ) (PDF file; 1.08 MB)
- ↑ W. Zheng, H. Kim, Q. Zhao: Comparative toxicokinetics of manganese chloride and methylcyclopentadienyl manganese tricarbonyl (MMT) in Sprague-Dawley rats. In: Toxicol. Sci. 54, 2, 2000, pp. 295-301, 10.1093 / toxsci / 54.2.295 .
- ^ United Nations Environment Program with the World Health Organization ; Manganese ; Geneva, 1981.
- ↑ General Motors: "2011 Chevrolet Malibu Owners Manual", 2010 ( Memento of December 5, 2010 in the Internet Archive )