Pentacarbonylhydridomanganese

Pentacarbonylhydridomanganese

Names
Other names Hydrogen pentacarbonylmanganate(−I) (7CI); Manganese, pentacarbonylhydro- (8CI); Hydridomanganese pentacarbonyl; Hydridopentacarbonylmanganese; Manganese pentacarbonyl hydride; Pentacarbonylhydromanganese; Pentacarbonylmanganese hydride
Identifiers
CAS Number	16972-33-1 Y
3D model (JSmol)	Interactive image
ChemSpider	25945809
PubChem CID	139143359
InChI InChI=1S/5CO.Mn.H/c5*1-2;; Key: SKOPWNLHPUYPLV-UHFFFAOYSA-N
SMILES O=C=[MnH](=C=O)(=C=O)(=C=O)=C=O
Properties
Chemical formula	HMn(CO)5
Molar mass	195.99799 g/mol
Appearance	At room temperature, it is liquid and colorless. Below its melting point, it may be sublimed in vacuum.[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). Y verify (what is YN ?) Infobox references

Pentacarbonylhydridomanganese is an organometallic compound with formula HMn(CO)₅. This compound is one of the most stable "first-row" transition metal hydrides.

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)

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] and its molecular point group is C_4v.^[5] The H-Mn bond length is 1.44 ± 0.03 Å.^[5] Gas phase electron diffraction analysis confirms these conclusions.

The pK_a 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