Methylcyclopentadienyl manganese tricarbonyl

• Tricarbonyl ( η5 -methylcyclopentadienyl ) manganese
• MMT

Dark orange liquid with a pleasant odor

Liquid

1.39 g · cm -3

2.2 ° C

231.6 ° C

0,063 mbar ( 20 ° C)

Very slightly soluble in water

Risk

• 8 mg · kg -1 ( LD50, rat, oral)
• 140 mg · kg -1 ( LD50, rat / rabbit, transdermal)

Template: Infobox chemical / molecular formula search available

( Methyl cyclopentadienyl ) manganese tricarbonyl (abbreviation: MMT or MCMT ) is a manganese compound with the half structural formula ( CH3C5H4 ) Mn (CO ) 3 The compound was first offered in 1958 as a replacement for tetraethyl lead additive, MMT was later used in unleaded fuel. Purpose was to increase the octane number.

Although MMT was banned as a gasoline additive in the United States from 1977 to 1995, it was used at this time in Canada since 1976. 1997-1998 it was no longer allowed due to discussions about health risks.

MMT is sold under the trade names HiTec 3000 and AK- 33X. From T2 Labs it is marketed under the name Ecotane.

History

Tetraethyllead (TEL) is older spark ignition engines, the additive of choice in order to reduce the knock by increasing the octane number. TEL was by Ethyl Corporation ( a joint venture of General Motors and DuPont) manufactured and sold. When the U.S. EPA in 1972 ordered the phasing out of Kraftstoffverbleiung, ethyl looking for alternatives. One of them was MMT, which from 1958 as smoke suppressants in gas turbines came into use and from 1974., As an additive in unleaded gasoline

1977, use of MMT was used as an additive in the U.S. as long as prohibited by the Clean Air Act, to ethyl manufacturer had proved that the additive does not lead to failure of the catalytic converters. As a result, a dispute between ethyl and EPA began in 1995, the Court of Appeal ruled that EPA had exceeded its powers. MMT was characterized in the U.S. to legally usable gasoline additive. MMT is currently ( part of Newmarket Corporation ) as well as Cestoil Chemical Inc. in Canada distributed by ethyl successor Afton Chemical Corporation (under the name Cestoburn ).

Production

Properties

( Methyl cyclopentadienyl ) manganese tricarbonyl is a dark orange, slightly volatile and difficult flammable liquid with a pleasant odor, which is very slightly soluble in water.

The compound is referred to as a half sandwich or piano-stool complex. The manganese atom in MMT is bonded to three carbonyl groups and a methyl cyclopentadienyl ring. These hydrophobic organic ligands make MMT highly lipophilic, which favors bioaccumulation.

Safety

The costs associated with MMT health risks are hotly debated and controversial for decades. A published study in Australia in 2003 leads to the conclusion that MMT highly toxic effect in concentrated form for people, but at the same time mentioned that the measured as a result of car exhaust gases with the use of MMT in the air manganese concentrations did not constitute a health risk. A study from 2002 ( Kitazawa et al. ) Pointed out that absorption through the skin in case of accidental fuel spillage, misuse of fuel as a solvent for degreasing and ( intentional ) Inhalation of vapors were the main routes of possible MMT exposure.

Persons who are exposed for a long time manganese, develop symptoms of Manganism which are similar to those of Parkinson's disease. For MMT, a cytotoxic effect was detected and specifically damage to dopaminergic PC-12 cells. Toxicokinetic studies have shown that manganese from MMT is added to the blood plasma of rats with the 37- times the rate of inorganic manganese.

Immediate symptoms of exposure to MMT are mild skin and eye irritation. Short-term symptoms associated with MMT poisoning include, among other things, headaches and vomiting and breathing difficulties. Animal studies have shown that long-term contact with MMT may result in liver and kidney damage.

The vapors of ( methyl cyclopentadienyl ) manganese tricarbonyl can combine with air to form an explosive mixture (flash point 96 ° C).

Recommendations from car manufacturers

Before the use of MMT is recommended to clarify whether the manufacturer, the use of MMT additives not recommended or. General Motors, for example, explicitly advises against it.