Pentacarbonylhydridomanganese
Chemical compound
From Wikipedia, the free encyclopedia
Pentacarbonylhydridomanganese is an organometallic compound with formula HMn(CO)5. This compound is one of the most stable "first-row" transition metal hydrides.
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| Names | |||
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| IUPAC name
Pentacarbonylhydridomanganese | |||
| Other names
Hydrogen pentacarbonylmanganate(−I) (7CI); Manganese, pentacarbonylhydro- (8CI); Hydridomanganese pentacarbonyl; Hydridopentacarbonylmanganese; Manganese pentacarbonyl hydride; Pentacarbonylhydromanganese; Pentacarbonylmanganese hydride | |||
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3D model (JSmol) |
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PubChem CID |
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| Properties | |||
| HMn(CO)5 | |||
| Molar mass | 195.99799 g/mol | ||
| Appearance | colorless liquid[1] | ||
| Acidity (pKa) | 7.1 | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Preparation
It was first reported in 1931.[2] Of the several ways to produce this compound,[3] is the protonation of the pentacarbonyl manganate anion. The latter is formed from reduction of dimanganese decacarbonyl, e.g., with superhydride:
- 2 LiHB(C2H5)3 + Mn2(CO)10 → 2 LiMn(CO)5 + H2 + 2 B(C2H5)3
- Li[Mn(CO)5] + CF3SO3H → HMn(CO)5 + CF3SO3Li
Salts of [Mn(CO)
5]−
can be isolated as crystalline PPN+
(μ-nitrido—bis-(triphenylphosphorus)) salt, which is smoothly protonated by CF
3SO
3H.[3]
- PPN[Mn(CO)
5] + CF
3SO
3H → HMn(CO)5 + PPN+
CF
3SO−
3
This compound can also be formed by the hydrolysis of pentacarbonyl(trimethylsilyl)manganese:[4]
- (CO)5MnSiMe3 + H2O → HMn(CO)5 + Me3SiOH (Me = CH3)
Structure and properties
The structure of HMn(CO)5 has been studied by many methods including X-ray diffraction, neutron diffraction, and electron diffraction.[5] HMn(CO)5 can be related to the structure of a hexacarbonyl complex such as Mn(CO)+
6, and therefore has similar properties.[6] The compound has octahedral symmetry,[7] its molecular point group is C4v and the H-Mn bond length is 1.44 ± 0.03 Å.[6] Gas phase electron diffraction analysis confirms these conclusions.
Main reactions
The pKa of HMn(CO)5 in water is 7.1.[8] It is thus comparable to hydrogen sulfide, a common inorganic acid, in its acidity.
A common reaction involving HMn(CO)5 is substitution of the CO ligands by organophosphines, as occurs both thermally and photochemically. In this way the many derivatives form of the type HMn(CO)5-x(PR3)x.[9] (R here need not be a purely hydrocarbon component; it may, for instance, be OEt, where Et = ethyl group.)
HMn(CO)5 can be used to reduce olefins and other organic compounds, as well as metal halides.[3]
It can be methylated with diazomethane.[1]
- HMn(CO)5 + CH2N2 → Mn(CO)5CH3 + N2