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Homework Problems Chapter 10

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    290615
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    Homework Problems

    Section 1

    Exercise 1

    Predict the charge n of cobaltocene (Co(Cp)2)n. Cp=cyclopentadienyl. Explain briefly.

    Answer

    +1, because the 18 electron rule is fulfilled.

    Exercise 2

    Bis-benzene chromium (Ƞ4-C6H6)Cr is a sandwich compound having two parallel benzene rings in an eclipsed conformation. Sketch the ligand group orbitals for this molecule.

    Answer

    clipboard_ea1119c83c6391c2bfbf64ef943c3b4b4.png

    Section 2

    Exercise 1

    The MO diagram of the CO molecule is given below. Identify the molecular orbitals that can act

    a) As sigma-donors

    b) Pi-acceptors in carbonyls.

    clipboard_e7b513409b01c290be4a89fe0a0e7b9af.png

    Answer

    a) 5 σ, 4 σ, bonding π orbitals

    b) anti-bonding π orbitals

    Exercise 2

    Which carbonyl will most likely exhibit the highest frequency for the C-O stretch vibration? Give a brief explanation for your decision.

    a) V(CO)6-

    b) Cr(CO)6

    c) Mn(CO)6+

    Answer

    c) Mn(CO)6+

    Carbonyl cations have the weakest pi-backbonding, therefore the bond order for the C-O bond is the highest and thus the frequency of the C-O stretch vibration is the highest.

    Exercise 3

    Predict the right charge of the most stable pentacarbonyl of

    a) Iron

    b) Mn

    c) Cr

    Answer

    a) 0

    b) 1-

    c) 2-

    Section 3

    Exercise 1

    What structure would you expect for a carbonyl made of the following fragments according to the concept of isolobality? Predict if the structure would likely be stable.

    a) Cr(CO)5+

    b) Cr(CO)4-

    c) Mn(CO)4-

    Answer

    a) 15VE -> tetrahedral cluster (not stable b/c CN too high)

    b) 15 VE -> tetrahedral cluster (not stable b/c CN too high)

    c) 16 VE -> trimer (stable b/c CN = 6, charge not too high).

    Exercise 2

    Which of the following fragments are isolobal to the CH2 fragment?

    a) NH2

    b) NH

    c) OH

    d) Fe(CO)3

    e) Co(CO)4+

    Answer

    b) NH

    Exercise 3

    Which of the following fragments are isolobal to the Mn(CO)5 fragment?

    a) CH3

    b) CH2CH3

    c) OH

    d) F

    e) NH

    Answer

    a) CH3

    b) CH2CH3

    c) OH

    d) F


    Homework Problems Chapter 10 is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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