Polynuclear Metal Carbonyls Overview
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Questions and Answers

What is the total Electron Accounting Number (EAN) of one manganese atom in the compound Mn2(CO)10?

  • 50
  • 36 (correct)
  • 25
  • 72

According to the 18-electron rule, how many total effective electrons should a stable metal carbonyl contain in the valence shell of one metal atom?

  • 18 (correct)
  • 16
  • 24
  • 20

How many electrons do the five terminal carbonyl groups donate to one manganese atom in Mn2(CO)10?

  • 10 (correct)
  • 12
  • 5
  • 8

What does the EAN rule determine regarding the bonding of metal atoms in metal carbonyl complexes?

<p>The electron donation from ligands to metal atoms (A)</p> Signup and view all the answers

In the compound Mn2(CO)10, how many electrons does the manganese-manganese bond contribute to the EAN of one manganese atom?

<p>1 (D)</p> Signup and view all the answers

What is the coordination number of each manganese atom in the Mn2(CO)10 molecule?

<p>6 (B)</p> Signup and view all the answers

Which type of hybridization does each manganese atom undergo in Mn2(CO)10?

<p>d2sp3 (B)</p> Signup and view all the answers

What is the electronic configuration of manganese in its free state?

<p>3d5 4s2 4p0 (B)</p> Signup and view all the answers

How many of the d-orbitals remain unhybridized in each manganese atom within Mn2(CO)10?

<p>3 (D)</p> Signup and view all the answers

In the hybridization process of Mn2(CO)10, which orbital becomes vacant?

<p>3dz2 (B)</p> Signup and view all the answers

What is the electronic configuration of manganese in Mn2(CO)10 after hybridization?

<p>3d7 4s0 (D)</p> Signup and view all the answers

What type of bond is formed between the two manganese atoms in Mn2(CO)10?

<p>Sigma bond (D)</p> Signup and view all the answers

Which molecular geometry does Mn2(CO)10 exhibit?

<p>Octahedral (B)</p> Signup and view all the answers

What occurs to the 4s electrons in manganese when forming the Mn2(CO)10 molecule?

<p>They are transferred to 3d orbitals. (D)</p> Signup and view all the answers

Which of the following methods yields the highest percentage of Mn2(CO)10?

<p>Reaction of Mn(CH3COO)2 with triethyl aluminium (B)</p> Signup and view all the answers

What is the role of the CO molecule in the formation of Mn2(CO)10?

<p>It provides lone pairs for sigma bond formation (B)</p> Signup and view all the answers

What character does Mn2(CO)10 exhibit due to the pairing of electrons?

<p>Diamagnetic character (A)</p> Signup and view all the answers

What is the effect of magnesium in the preparation of Mn2(CO)10?

<p>It acts as a reducing agent (C)</p> Signup and view all the answers

What percentage yield is achieved in the carbonylation of MnCl2 in the presence of benzophenone ketyl?

<p>35% (A)</p> Signup and view all the answers

In the molecular structure of Mn2(CO)10, how many CO groups are bonded to each manganese atom?

<p>Five (B)</p> Signup and view all the answers

What is the oxidation state of manganese in Mn2(CO)10?

<p>0 (B)</p> Signup and view all the answers

What is the melting point of Mn2(CO)10?

<p>155°C (C)</p> Signup and view all the answers

Which halogen has the highest reactivity with Mn2(CO)10?

<p>Iodine (B)</p> Signup and view all the answers

What is formed when Mn2(CO)10 is reduced with hydrogen under 200 atm pressure at 200°C?

<p>HMn(CO)5 (D)</p> Signup and view all the answers

What type of bond is broken when Mn2(CO)10 reacts with lithium or sodium?

<p>Mn−Mn bond (A)</p> Signup and view all the answers

Which of the following statements is true regarding the diamagnetic nature of Mn2(CO)10?

<p>All electrons in Mn2(CO)10 are paired. (D)</p> Signup and view all the answers

Which solvent is used with sodium to break the Mn−Mn bond in Mn2(CO)10?

<p>Liquid ammonia (D)</p> Signup and view all the answers

What type of compounds are formed when Mn2(CO)10 reacts with phosphines, arsines, and stilbines?

<p>Paramagnetic compounds (D)</p> Signup and view all the answers

What is the resultant ion when Mn2(CO)10 reacts with lithium in tetrahydrofuran?

<p>Li+[Mn(CO)5]- (B)</p> Signup and view all the answers

What is the electronic configuration of a free cobalt atom?

<p>1s2 2s2 2p6 3s2 3p6 3d7 4s2 (A)</p> Signup and view all the answers

Which hybridization occurs in the cobalt atom within the Co2(CO)8 molecule?

<p>dsp3 (B)</p> Signup and view all the answers

How many Co–C bonds are formed by one bridging carbonyl group in Co2(CO)8?

<p>Two (A)</p> Signup and view all the answers

Which of the following represents the hybridized electron orbitals in a Co atom of the Co2(CO)8 molecule?

<p>Six d2sp3 hybrid orbitals (B)</p> Signup and view all the answers

What is the common notation for the two types of carbonyl groups mentioned in Co2(CO)8?

<p>Terminal and bridging (B)</p> Signup and view all the answers

Which of the following statements about the d2sp3 hybridization in Co is least accurate?

<p>It leads to the formation of octahedral geometry. (C)</p> Signup and view all the answers

In the free state, which electron configuration is altered when cobalt forms Co2(CO)8?

<p>The 3d and 4s orbitals change occupancy. (B)</p> Signup and view all the answers

How does the structure of the Co2(CO)8 molecule differ from that of a free cobalt atom?

<p>It exhibits covalent bonding with carbonyl groups. (A)</p> Signup and view all the answers

What product is formed when Co2(CO)8 is subjected to thermal decomposition at 50°C?

<p>Co4(CO)12 (B)</p> Signup and view all the answers

Which of the following is a result of the action of air on Co2(CO)8?

<p>Conversion into a deep violet basic carbonate (B)</p> Signup and view all the answers

Under which conditions is Co2(CO)8 reduced to cobalt hydride?

<p>At 165°C and 120 atm (D)</p> Signup and view all the answers

What is the outcome of Co2(CO)8 reacting with strong bases like ammonia?

<p>Proportionation into Co(+2) and CO(-1) (B)</p> Signup and view all the answers

What compound is formed when Co2(CO)8 reacts with NO?

<p>Co(CO)3NO (A)</p> Signup and view all the answers

What is the primary result of the reaction between Co2(CO)8 and halogens?

<p>Production of CoX2 and CO (A)</p> Signup and view all the answers

Which of the following best describes Co(CO)3NO after formation?

<p>NO group is more firmly held than CO groups (B)</p> Signup and view all the answers

Flashcards

EAN rule for metal carbonyls

The EAN rule states that the total number of electrons on a metal atom in a metal carbonyl, including those donated by the carbonyl ligands, equals the number of electrons in the next noble gas.

EAN of Mn in Mn2(CO)10

The effective atomic number (EAN) of each manganese atom in Mn2(CO)10 is 36, which is the same as krypton (Kr).

18-Electron rule in metal carbonyls

The 18-electron rule states that stable metal carbonyls have 18 electrons in the valence shell of the metal.

Mn2(CO)10 structure

Manganese complex containing two Mn atoms and 10 CO ligands. It is a polynuclear metal carbonyl.

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Metal carbonyl bonding

In metal carbonyls, CO ligands donate electron pairs to the central metal atom through a sigma bond. This results in the formation of a metal-carbon bond.

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Coordination number of Mn in Mn2(CO)10

Each Mn atom in Mn2(CO)10 has six sigma bonds: five with terminal carbonyl ligands and one with the other Mn atom.

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Hybridization of Mn in Mn2(CO)10

The Mn atom in Mn2(CO)10 undergoes d2sp3 hybridization due to its six sigma bonds, resulting in an octahedral geometry.

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Mn electronic configuration in Mn2(CO)10

The 4s electrons of Mn in its free state move to the 3d orbitals, resulting in a 3d7 4s0 4p0 configuration in Mn2(CO)10.

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How does Mn achieve d2sp3 hybridization?

In Mn2(CO)10, the 3dz2 orbital of Mn becomes vacant to allow for d2sp3 hybridization, which involves six orbitals: 3dx2-y2, 3dz2, 4s, 4px, 4py, and 4pz.

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What orbitals are involved in Mn2(CO)10 bonding?

In Mn2(CO)10, six d2sp3 hybrid orbitals of Mn participate in sigma bonding with the carbonyl ligands and the other Mn atom. The remaining 3d orbitals (3dxy, 3dyz, 3dzx) remain unhybridized.

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Why is Mn2(CO)10 non-bridged?

The Mn2(CO)10 structure is non-bridged because each Mn atom is directly bonded to the other Mn atom and has six sigma bonds with terminal carbonyl ligands, resulting in a closed-shell configuration.

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What is the geometry of Mn2(CO)10?

The Mn2(CO)10 molecule exhibits an octahedral geometry around each Mn atom due to the d2sp3 hybridization.

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Mn2(CO)10 Hybridization

In Mn2(CO)10, the manganese atom is in a d2sp3 hybridized state, using two d orbitals, one s orbital, and three p orbitals to form six hybrid orbitals.

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Mn-Mn Bond in Mn2(CO)10

The Mn-Mn bond in Mn2(CO)10 is formed by the overlap of two singly-filled d2sp3 hybrid orbitals, one from each manganese atom.

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CO-Mn Bond in Mn2(CO)10

The CO-Mn bond in Mn2(CO)10 is a coordinate sigma bond formed by the donation of a lone pair of electrons from the sp hybrid orbital of the carbon atom in CO to a vacant d2sp3 hybrid orbital on the Mn atom.

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Mn2(CO)10 Diamagnetism

Mn2(CO)10 exhibits diamagnetism because the pairing of electrons occurs through the formation of the Mn-Mn bond.

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Preparation of Mn2(CO)10 (Method 1)

Mn2(CO)10 can be prepared by the carbonylation of manganese iodide (MnI2) with carbon monoxide (CO) using magnesium (Mg) as a reducing agent.

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Preparation of Mn2(CO)10 (Method 2)

Mn2(CO)10 can be prepared by reducing MnI2 with Mg in diethyl ether under high pressure of CO.

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Preparation of Mn2(CO)10 (Method 3)

Mn2(CO)10 can be prepared by reacting manganese acetate (Mn(CH3COO)2) with triethylaluminium ((C2H5)3Al) under CO at elevated temperature and pressure.

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Preparation of Mn2(CO)10 (Method 4)

Mn2(CO)10 can be prepared by carbonylation of MnCl2 in the presence of benzophenone ketyl (C6H5)2CONa at elevated temperature.

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Co atom electronic configuration

The electronic configuration of a cobalt atom in its free state is 1s2 2s2 2p6 3s2 3p6 3d7 4s2. This means it has 27 electrons distributed across different energy levels.

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Co atom in Co2(CO)8

In the Co2(CO)8 molecule, each cobalt atom undergoes dsp3 hybridization. This results in an electronic configuration of 3d8 4s1 4p0, where one electron from the 4s orbital is promoted to the 3d orbital.

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What is dsp3 hybridization?

dsp3 hybridization involves mixing one d, one s and three p atomic orbitals to form six hybrid orbitals oriented in a square planar geometry. This is typical for transition metal complexes.

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How does Co2(CO)8 form?

The Co2(CO)8 molecule forms by the overlap of singly filled d2sp3 hybrid orbitals on two Co atoms with the sp2 hybrid orbitals of carbon atoms in bridging carbonyl ligands. Two bridging carbonyl groups contribute electrons to the formation of the Co-C bonds.

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What are bridging carbonyl groups?

Bridging carbonyl groups in Co2(CO)8 are CO ligands that are bonded to both metal centers. These groups act as bridges connecting the two cobalt atoms.

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Terminal vs. bridging carbonyl groups

Terminal carbonyl groups are directly bound to only one metal atom, while bridging carbonyl groups are connected to two metal atoms. Both contribute electrons to the metal-carbonyl bond.

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Co2(CO)8 structure

Co2(CO)8 has a structure with two cobalt atoms bridged by two carbonyl groups. Each cobalt atom is further coordinated to four terminal carbonyl groups.

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Mn2(CO)10 Preparation

Mn2(CO)10 is synthesized by reacting (CH3C5H4)Mn(CO)3 with sodium under high pressure and temperature, releasing carbon monoxide as a byproduct.

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Mn2(CO)10 Properties

Mn2(CO)10 is a golden-yellow crystalline solid that melts around 155°C and sublimes readily in vacuum. It is air-sensitive and readily oxidized in solution, requiring storage under inert atmosphere.

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Mn2(CO)10 Halogenation

Halogenation breaks the Mn-Mn bond in Mn2(CO)10, forming manganese carbonyl halides (Mn(CO)5X) where X represents the halogen. The reactivity of the halogens is in the order: I > Br > Cl.

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Mn2(CO)10 Reaction with Li/Na

Li in THF and Na in liquid NH3 react with Mn2(CO)10, breaking the Mn-Mn bond and generating [Mn(CO)5]- anions, where Mn has a -1 oxidation state.

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Mn2(CO)10 Reduction

Reducing Mn2(CO)10 with hydrogen under high pressure and temperature yields carbonyl hydride, HMn(CO)5.

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Mn2(CO)10 with Phosphines

Mn2(CO)10 reacts with phosphines, arsines, and stilbines to produce monomeric, paramagnetic compounds of the type Mn(CO)4(PR3), where R represents a substituent group.

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Dicobalt octacarbonyl

A compound with the formula Co2(CO)8, it is an orange-brown solid, soluble in organic solvents like alcohol and ether. Air sensitive, it decomposes into Co4(CO)12 upon heating.

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Thermal decomposition of Co2(CO)8

When heated, dicobalt octacarbonyl (Co2(CO)8) decomposes into tetracobalt dodecacarbonyl (Co4(CO)12) and carbon monoxide. This reaction occurs at 50°C in an inert atmosphere.

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Reaction of Co2(CO)8 with air

Exposure to air converts dicobalt octacarbonyl into a deep violet basic carbonate of cobalt.

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Reduction of Co2(CO)8 with H2

Hydrogen gas (H2) reduces dicobalt octacarbonyl to cobalt hydride, H+[Co(CO)4]-, under high pressure and temperature.

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Disproportionation reaction of Co2(CO)8

A reaction where Co2(CO)8 breaks down into different oxidation states of cobalt, forming cobalt(I) and cobalt(II) complexes.

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Reaction of Co2(CO)8 with NO

NO reacts with dicobalt octacarbonyl to form cobalt tricarbonyl nitrosyl (Co(CO)3NO), releasing carbon monoxide.

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Reaction of Co2(CO)8 with halogens

Halogens (like chlorine, bromine) decompose dicobalt octacarbonyl, producing cobalt halides and releasing carbon monoxide.

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Cobalt carbonyl stability

Cobalt carbonyls form stable compounds due to the strong metal-carbonyl bonding, where carbon monoxide donates electrons to the cobalt atom, contributing to the overall stability.

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Study Notes

Polynuclear Metal Carbonyls

  • Metal carbonyls are complexes of metals bonded to carbon monoxide (CO) molecules.
  • EAN Rule: The total number of electrons on the metal atom, including those gained from CO, equals the number of electrons in the next noble gas.
  • Example: Mn₂(CO)₁₀. Electrons from two Mn atoms (2 × 25 = 50) + electrons from 10 CO groups (10 × 2 = 20) + electrons from one Mn-Mn bond (2) =72. Therefore, EAN of one Mn atom is 36 (same as krypton).

Alternative Method

  • EAN of Mn in Mn₂(CO)₁₀ can be calculated by adding the atomic number of Mn (25) to the electrons donated by five terminal carbonyl groups (5 × 2 = 10) and the electrons from the Mn-Mn bond (1 × 2 = 2). This equals 36, corresponding to the krypton electron configuration.

18-Electron Rule

  • In a stable metal carbonyl, the metal atom has 18 valence shell electrons. This number is calculated by adding the number of valence electrons in the free metal ion, twice the number of CO ligands, and twice the number of metal-metal bonds.
  • Example: In Mn₂(CO)₁₀, each Mn has 18 electrons.

Structure and Bonding in Mn₂(CO)₁₀

  • The structure of Mn₂(CO)₁₀ consists of two Mn pentacarbonyl groups joined by an Mn-Mn bond.
  • Each Mn is bonded to five terminal CO ligands.
  • The molecule is diamagnetic.

Structure and Bonding in Co₂(CO)₈

  • In solution, Co₂(CO)₈ has a non-bridged structure, with each Co bonded to four terminal CO ligands and another Co through a Co-Co bond. Therefore, the EAN of each Co atom is 36.
  • In the solid state, Co₂(CO)₈ possesses a bridged structure, with each Co atom bonded to three terminal CO ligands, two bridging CO groups, and another Co atom through a Co-Co bond. In the solid state, the EAN for each Co atom remains 36.

Preparations of Manganese Decacarbonyl

  • Mn₂(CO)₁₀ can be prepared using several methods, for example, by carbonylation of manganese iodide with carbon monoxide and magnesium as a reducing agent, or reacting MnI₂ with magnesium in diethyl ether under high CO pressure.
  • Other methods involving triethylaluminum and different reactants also exist.

Properties of Manganese Decacarbonyl

  • Mn₂(CO)₁₀ is a yellow crystalline solid.
  • It sublimes in a vacuum, and is soluble in organic solvents.
  • It slowly oxidizes in air.

Properties of Dicobalt Octacarbonyl

  • Co₂(CO)₈ is an orange-brown crystalline solid that sublimes readily.
  • It's soluble in alcohol, ether, and carbon tetrachloride.
  • It's air-sensitive both in the solid and liquid states.
  • It decomposes at high temperatures in an inert atmosphere to form Co₄(CO)₁₂.

Reactions of Metal Carbonyls

  • Various reactions can occur, such as halogenation, reduction with hydrogen, or reactions with phosphines, arines, stilbines, or NO.

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Description

This quiz covers the essential concepts of polynuclear metal carbonyls, including the Electron Activity Number (EAN) Rule and the 18-Electron Rule. Example calculations illustrate how to determine the EAN of manganese in its metal carbonyl complex. Perfect for students studying inorganic chemistry.

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