Pentacarbonylhydridomanganese
Encyclopedia
Pentacarbonylhydridomanganese is an organometallic compound with formula HMn(CO)5. This compound is one of the most stable “first-row” transition metal hydride
s.
(Mn(CO)5)2. The reaction is shown below.
Li(C2H5)3BH + ½Mn2(CO)10 → Li[Mn(CO)5] + ½H2 + (C2H5)3B
Li[Mn(CO)5] + CF3SO3H → HMn(CO)5 +
Salts of can be isolated as crystalline (μ-nitrido—bis-(triphenylphosphorus)) salt, which is smoothly protonated by CF3SO3H.
PPN[Mn(CO)5] + CF3SO3H → HMn(CO)5 +
This compound can also be formed by the reaction of a solution of pentacarbonyl(trimethylsilyl)manganese with water. The reaction is shown below.
2(CO)5MnSiMe3 + H2O → HMn(CO)5 + Me3SiOSiMe3
is 1.44 ± 0.03 Å. A gas phase electron diffraction study confirms this data.
The structure of HMn(CO)5 has been studied by many methods including X-Ray diffraction, neutron diffraction
, and electron diffraction. HMn(CO)5 can be related to the structure of a hexacarbonyl complex such as , and therefore has the following similar properties. The occupied molecular orbitals on the top are the 2 t2g orbitals. They are characterized as metal 3dπ orbitals. Since the antibonding 2π orbitals interact with the carbonyl groups, (or in this case) the t2g orbital is stabilized compared to the 3dπ orbital, which in turn will cause changes in the sigma and pi interactions.
of HMn(CO)5 is 15.1. It is thus comparable to hydrogen sulfide
, a common inorganic acid, in its acidity.
A common reaction involving the HMn(CO)5 species is substitution of the CO ligands by organophosphines, as occurs both thermally and photochemically. In this way the following derivatives form MnH(CO)3P2, MnH(CO)2P3, and MnH(CO)P4, (where P = P(OEt)3, PPh(OEt)2, PPh2OEt, PPh(OiPr)2.
The compound HMn(CO)5 can be used to reduce olefins and other organic compounds, as well as metal halides.
Carbonyl ligands are substituted in this complex with the appropriate phosphite, resulting in the complexes shown above.
This compound can be methylated with diazomethane
.
Transition metal hydride
Transition metal hydrides are chemical compounds containing a transition metal bonded to hydrogen. Most transition metals form hydride complexes and some are significant in various catalytic and synthetic reactions...
s.
Preparation
It was first reported in 1931. Of the several ways to produce this compound, is the protonation of the pentacarbonyl manganate anion. The latter is formed from reduction of dimanganese decacarbonylDimanganese decacarbonyl
Dimanganese decacarbonyl is the chemical compound with the formula Mn210. This metal carbonyl is an important reagent in the organometallic chemistry of manganese.-Synthesis:...
(Mn(CO)5)2. The reaction is shown below.
Li(C2H5)3BH + ½Mn2(CO)10 → Li[Mn(CO)5] + ½H2 + (C2H5)3B
Li[Mn(CO)5] + CF3SO3H → HMn(CO)5 +
Salts of can be isolated as crystalline (μ-nitrido—bis-(triphenylphosphorus)) salt, which is smoothly protonated by CF3SO3H.
PPN[Mn(CO)5] + CF3SO3H → HMn(CO)5 +
This compound can also be formed by the reaction of a solution of pentacarbonyl(trimethylsilyl)manganese with water. The reaction is shown below.
2(CO)5MnSiMe3 + H2O → HMn(CO)5 + Me3SiOSiMe3
Structure and Properties
The compound has octahedral symmetry and its molecular point group is C4v. The H-Mn bond lengthBond length
- Explanation :Bond length is related to bond order, when more electrons participate in bond formation the bond will get shorter. Bond length is also inversely related to bond strength and the bond dissociation energy, as a stronger bond will be shorter...
is 1.44 ± 0.03 Å. A gas phase electron diffraction study confirms this data.
The structure of HMn(CO)5 has been studied by many methods including X-Ray diffraction, neutron diffraction
Neutron diffraction
Neutron diffraction or elastic neutron scattering is the application of neutron scattering to the determination of the atomic and/or magnetic structure of a material: A sample to be examined is placed in a beam of thermal or cold neutrons to obtain a diffraction pattern that provides information of...
, and electron diffraction. HMn(CO)5 can be related to the structure of a hexacarbonyl complex such as , and therefore has the following similar properties. The occupied molecular orbitals on the top are the 2 t2g orbitals. They are characterized as metal 3dπ orbitals. Since the antibonding 2π orbitals interact with the carbonyl groups, (or in this case) the t2g orbital is stabilized compared to the 3dπ orbital, which in turn will cause changes in the sigma and pi interactions.
Main Reactions
The pKaPKA
PKA, pKa, or other similar variations may stand for:* pKa, the symbol for the acid dissociation constant at logarithmic scale* Protein kinase A, a class of cAMP-dependent enzymes* Pi Kappa Alpha, the North-American social fraternity...
of HMn(CO)5 is 15.1. It is thus comparable to hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
, a common inorganic acid, in its acidity.
A common reaction involving the HMn(CO)5 species is substitution of the CO ligands by organophosphines, as occurs both thermally and photochemically. In this way the following derivatives form MnH(CO)3P2, MnH(CO)2P3, and MnH(CO)P4, (where P = P(OEt)3, PPh(OEt)2, PPh2OEt, PPh(OiPr)2.
The compound HMn(CO)5 can be used to reduce olefins and other organic compounds, as well as metal halides.
Carbonyl ligands are substituted in this complex with the appropriate phosphite, resulting in the complexes shown above.
This compound can be methylated with diazomethane
Diazomethane
Diazomethane is the chemical compound CH2N2. It is the simplest of diazo compounds. In the pure form at room temperature, it is a extremely sensitive explosive yellow gas, thus it is almost universally used as a solution in diethyl ether...
.
- HMn(CO)5 + CH2N2 → Mn(CO)5CH3 + N2