Dimanganese decacarbonyl is the
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
with the
formula Mn
2(CO)
10. This
metal carbonyl
Metal carbonyls are coordination complexes of transition metals with carbon monoxide ligands. Metal carbonyls are useful in organic synthesis and as catalysts or catalyst precursors in homogeneous catalysis, such as hydroformylation and Reppe c ...
is an important
reagent in the
organometallic chemistry of
manganese
Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...
.
Synthesis
The compound was first prepared in low yield by the reduction of manganese iodide with
magnesium
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
under
CO.
[Brimm, E. O.; Lynch, M. A.; Sesny, W. J. "Preparation and Properties of Manganese Carbonyl" Journal of the American Chemical Society 1954, volume 76, page 3831 - 3835.] A more efficient preparation entails reduction of anhydrous
MnCl2 with sodium
benzophenone
Benzophenone is the organic compound with the formula (C6H5)2CO, generally abbreviated Ph2CO. It is a white solid that is soluble in organic solvents. Benzophenone is a widely used building block in organic chemistry, being the parent diarylket ...
ketyl under 200 atmospheres of CO. The availability of inexpensive
methylcyclopentadienyl manganese tricarbonyl ("MMT") has led to a low pressure route to Mn
2(CO)
10.
Structure
The crystal structure of Mn
2(CO)
10 was redetermined at high precision at room temperature in 1981
and bond lengths mentioned herein refer to results from that study. Mn
2(CO)
10 has no bridging CO ligands: it can be described as containing two axially-linked (CO)
5Mn- subunits. There are two kinds of CO ligands; there is one CO linked to each Mn atom that is coaxial with the Mn-Mn bond and there are four “equatorial” carbonyls bonded to each Mn atom that are nearly perpendicular to the Mn-Mn bond (Mn’-Mn-CO(equatorial) angles range from 84.61(7) to 89.16(7) degrees). The axial carbonyl distance of (181.1
pm) is 4.5
pm shorter than the average equatorial manganese-carbonyl distance of 185.6
pm. In the stable rotamer, the two Mn(CO)
5 subunits are
staggered. Thus, the overall molecule has approximate
point group D
4d symmetry, which is an uncommon symmetry shared with
S2F10.
[L. F. Dahl, E. Ishishi, R. E. Rundle "Polynuclear Metal Carbonyls. I. Structures of Mn2(CO)10 and Re2(CO)10 J. Chem. Phys. 1957, volume 26, p. 1750. ] The Mn
2(CO)
10 molecule is isomorphous with
Re2(CO)10 and the corresponding decacarbonyl of Tc.
Reactions
Mn
2(CO)
10 is air stable as a crystalline solid, but solutions require
Schlenk techniques. It finds limited use in
organic synthesis.
[Pauson, P. L. "Decacarbonyldimanganese" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. .] Characteristic reactions:
*Reduction of Mn
2(CO)
10 gives the manganese pentacarbonyl anion, which can be isolated as a
salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...
:
:Mn
2(CO)
10 + 2 Na → 2 Na
n(CO)5The anion is a versatile nucleophile. Protonation gives the
hydride
In chemistry, a hydride is formally the anion of hydrogen( H−). The term is applied loosely. At one extreme, all compounds containing covalently bound H atoms are called hydrides: water (H2O) is a hydride of oxygen, ammonia is a hydride ...
Mn(CO)5 and methylation gives
CH3)Mn(CO)5
*Bromination of Mn
2(CO)
10 proceeds with scission of the Mn-Mn bond to give
manganese pentacarbonyl bromide.
:Mn
2(CO)
10 +
Br2 → 2
n(CO)5Br
*
Homolysis of Mn
2(CO)
10 by either heat or light gives the ·Mn(CO)
5 radical, allowing Mn
2(CO)
10 to be used as an
initiator
An initiator can refer to:
* A person who instigates something.
* Modulated neutron initiator, a neutron source used in some nuclear weapons
** Initiator, an Explosive booster
** Initiator, the first Nuclear chain reaction
* Pyrotechnic initiato ...
for various polymerization reactions.
Safety
Mn
2(CO)
10 is a volatile source of a metal and a source of CO.
References
{{DEFAULTSORT:Dimanganese Decacarbonyl
Carbonyl complexes
Organomanganese compounds