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Answers to CHEM 102 Study Guide on Coordination Chemistry

  1. Define:

    1. cis - a stereochemical geometry where two like ligands are coordinated adjacent to each other in a complex.

    2. trans - stereochemical geometry where two like ligands are coordinated 180 degrees from each other.

    3. fac - a stereochemical geometry where three like ligands define one face of an octahedron in an octahedral complex.

    4. - a stereochemical geometry wherre three like ligands in a n octahedral complex are coordinated in the same plane going around the metal center.

    5. ligand - an ion or molecule that coordinates to a metal atom or metal ion to form a complex.

    6. sigma-donor ligand - a ligand that acts as a Lewis base donating electrons from a lone pair to the metal center.

    7. pi-acceptor ligand - ligand that donates a pair of electrons from a lone pair to the metal center but also has the ability to accept electron density from the metal d orbitals into either d orbitals or pi-antibonding orbitals.

    8. chelating ligand - a ligand able to occupy two or more sites in the coordination sphere of a complex, usually donating two or more pairs of electrons to the metal center.

    9. monodentate - refers to a ligand that donates only one electron pair to a ligand, it is not a chelating ligand (agent)

    10. multidentate - refers to a ligand that donates more than one pair of electrons to a metal center, a chelating ligand (agent)

    11. bidentate - refers to a ligand that donates two pairs of electrons to a metal center, a chelating ligand (agent)

    12. coordination sphere isomerism - refers to structural isomerism of coordination complexes in which the lignds in the inner coordination sphere differ.

    13. linkage isomerism - refers to structural isomers of coordination compounds in which a ligand differs in its mode of attachment to a metal ion.

    14. structural isomerism - refers to compounds which have the same formula but having differing bonding arrangements of the atoms.

    15. stereosiomerism - refers to compounds having the same formula and bonding arrangement but differing in the spatial arrangements of the atoms (cis, trans, fac, mer, a, eq, and optical isomers)

    16. enantiomers - isomers which are non-superimposable mirror images of each other

    17. dextrorotary - describes and enantiomer which rotates plane polarized light to the right

    18. levorotary - describes an enantiomer which rotates plane polarized light to the left

  2. What is the oxidation state of the central atom in the compounds below?

    1. RhCl3. 3 H2O

      Rh3+, 18 electrons around Rh, name: triaquotrichlororhodium (III)



    2. Co2+, 19 electrons around Co, name: hexacyanocobaltate (II) ion



    3. Fe2+, 18 electrons around Fe, name: bromodicarbonylcyclopentaidenyliron (II)



    4. Fe3+, 17 electrons around Fe, name: fac-triamminetrithiocyanatoiron (III)



    5. Cr0, 18 electrons around Cr, name: benzenetricarbonylchromium (0)

  3. What type of isomerism is demonstrated by the pairs of compounds below?



    1. linkage isomerism, Fe3+ for both structures, 17 electrons around Fe for both structures, name: left: hexathiocyanatoferrate (III) ion, right: hexaisothiocyanatoferrate (III) ion



    2. coordination sphere isomerism, Co2+ for each structure , 19 electrons around Co for each structure, name: left: hexaaquocobalte (II) chloride, right: tetraaquodichlorocobalt (II) dihydrate



    3. optical isomerism, Ni2+ for each structure, 16 electrons around Ni for each structure, name: bromocarbonylchloro(triphenylphosphine)nickel (II), determination of R & S beyond scope of CHEM 102



    4. cis-trans isomerism, Pt2+ for both structures, 16 electrons around Pt for both structures, name: left: cis-diamminedichloroplatinum (II), right: trans-diamminedichloroplatinum (II)





    fac-mer isomerism, Fe3+ for both structures, 17 electrons around Fe in each structure, name: left: fac-triamminetribromoiron (III), right: mer-triamminetribromoiron (III)

  4. Name all the compounds on the study guide using IUPAC nomenclature rules.

    Compounds are named in each example.

  5. How many electrons are around the central metal atom for all the drawn structures on the study guide? (including those below)

    Compounds have electron counts indicated in each example.



    1. 8 electrons around Ti, Ti4+, name: tetrachlorotitanium (IV)



    2. 16 electrons around Ni, Ni2+, name: dichlorobis(triphenylphosphine)nickel (II)



    3. 18 electrons around Ti, Ti2+, name: dicarbonylbis(cyclopentadienyl)titanium (II)



    4. 18 electrons around Fe, Fe0, name: (eq)tricarbonyl(a)bis(triphenylphosphine)iron (0)




  6. Classify the ligands belowas to whether they are i) anionic or neutral, ii) σ-donor or π-acceptor ligands, iii) monodentate or multidentate, and iv) what number of electrons they donate to the metal center.

    C=O
    neutral
    π-acceptor
    monodentate
    2 e-donor
    H2O
    neutral
    &sigma:-donor
    monodentate
    2 e-donor
    C=N-
    anionic
    π-acceptor
    monodentate
    2 e-donor
    Br-
    anionic
    &sigma:-donor
    monodentate
    2 e-donor
    NH3
    neutral
    &sigma:-donor
    monodentate
    2 e-donor
    H2NCH2CH2NH2
    neutral
    σ-donor
    multidentate
    4 e- donor
    CH3CO2-
    anionic
    π-acceptor
    monodentate
    2 e-donor
    H2C=CH2
    neutral
    π-acceptor
    monodentate
    2 e-donor
    I-
    anionic
    σ-donor
    monodentate
    2 e-donor

    NO2-
    anionic
    π-acceptor
    monodentate
    2 e-donor
    Ph2PCH2CH2PPh2
    neutral
    π-acceptor
    multidentate
    4 e-donor
    Cl-
    anionic
    σ-donor
    monodentate
    2 e-donor