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Problem 71b
Sketch the structure of the complex in each of the following compounds and give the full compound name:
b. Na2[Ru(H2O)Cl5]
Problem 71c
Sketch the structure of the complex in each of the following compounds and give the full compound name:
c. trans-NH3[Co(C2O4)2(H2O)2]
Problem 71d
Sketch the structure of the complex in each of the following compounds and give the full compound name:
d. cis-[Ru(en)2Cl2]
- Complete the exercises below. Which complex ions in Exercise 23.71 have optical isomers?
Problem 72
Problem 73
The molecule dimethylphosphinoethane [(CH3)2PCH2CH2P(CH3)2, which is abbreviated dmpe] is used as a ligand for some complexes that serve as catalysts. A complex that contains this ligand is Mo(CO)4(dmpe) .
a. Draw the Lewis structure for dmpe, and compare it with ethylenediamine as a coordinating ligand.
b. What is the oxidation state of Mo in Na2[Mo(CN)2(CO)2(dmpe)] ?
c. Sketch the structure of the [Mo(CN)2(CO)2(dmpe)]2- ion, including all the possible isomers.
- Complete the exercises below. The square-planar complex [Pt(en) Cl₂] only forms in one of two possible geometric isomers. Which isomer is not observed: cis or trans?
Problem 74
- Complete the exercises below. Which transition metal atom is present in each of the following biologically important molecules: a. hemoglobin, b. chlorophylls, c. siderophores, d. hemocyanin?
Problem 76
Problem 77
Carbon monoxide, CO, is an important ligand in coordination chemistry. When CO is reacted with nickel metal, the product is [Ni(CO)4] which is a toxic, pale yellow liquid.
a. What is the oxidation number for nickel in this compound?
b. Given that [Ni(CO)4] is a diamagnetic molecule with a tetrahedral geometry, what is the electron configuration of nickel in this compound?
c. Write the name for [Ni(CO)4] using the nomenclature rules for coordination compounds.
- Complete the exercises below. Which of the following objects is chiral: a. a left shoe, b. a slice of bread, c. a wood screw, d. a molecular model of Zn(en)Cl₂, e. a typical golf club?
Problem 79
- Complete the exercises below. Solutions of [Co(NH₃)₆]²⁺, [Co(H₂O)₆]²⁺ (both octahedral), and [CoCl₄]²⁻ (tetrahedral) are colored. One is pink, one is blue, and one is yellow. Based on the spectrochemical series and remembering that the energy splitting in tetrahedral complexes is normally much less than that in octahedral ones, assign a color to each complex.
Problem 82
- Complete the exercises below. Oxyhemoglobin, with an O₂ bound to iron, is a low-spin Fe(II) complex; deoxyhemoglobin, without the O₂ molecule, is a high-spin complex. d. A 15-minute exposure to air containing 400 ppm of CO causes about 10% of the hemoglobin in the blood to be converted into the carbon monoxide complex, called carboxyhemoglobin. What does this suggest about the relative equilibrium constants for the binding of carbon monoxide and O₂ to hemoglobin? e. CO is a strong-field ligand. What color might you expect carboxyhemoglobin to be?
Problem 83
- Complete the exercises below. Consider the tetrahedral anions VO₄³⁻ (orthovanadate ion), CrO₄²⁻ (chromate ion), and MnO₄⁻ (permanganate ion). a. These anions are isoelectronic. What does this statement mean? b. Would you expect these anions to exhibit d-d transitions? Explain. c. As mentioned in “A Closer Look” on charge-transfer color, the violet color of MnO₄⁻ is due to a ligand-to-metal charge transfer (LMCT) transition. What is meant by this term? d. The LMCT transition in MnO₄⁻ occurs at a wavelength of 565 nm. The CrO₄²⁻ ion is yellow. Is the wavelength of the LMCT transition for chromate larger or smaller than that for MnO₄⁻? Explain. e. The VO₄³⁻ ion is colorless. Do you expect the light absorbed by the LMCT to fall in the UV or the IR region of the electromagnetic spectrum? Explain your reasoning.
Problem 84
- Complete the exercises below. Given the colors observed for VO₄³⁻ (orthovanadate ion), CrO₄²⁻ (chromate ion), and MnO₄⁻ (permanganate ion) (see Exercise 23.84), what can you say about how the energy separation between the ligand orbitals and the empty d orbitals changes as a function of the oxidation state of the transition metal at the center of the tetrahedral anion?
Problem 85
- Complete the exercises below. The red color of ruby is due to the presence of Cr(III) ions at octahedral sites in the close-packed oxide lattice of Al₂O₃. Draw the crystal-field splitting diagram for Cr(III) in this environment. Suppose that the ruby crystal is subjected to high pressure. What do you predict for the variation in the wavelength of absorption of the ruby as a function of pressure? Explain.
Problem 86
- Complete the exercises below. In 2001, chemists at SUNY-Stony Brook succeeded in synthesizing the complex trans-[Fe(CN)₄(CO)₂]²⁻, which could be a model of complexes that may have played a role in the origin of life. a. Sketch the structure of the complex. b. The complex is isolated as a sodium salt. Write the complete name of this salt. c. What is the oxidation state of Fe in this complex? How many d electrons are associated with the Fe in this complex? d. Would you expect this complex to be high spin or low spin? Explain.
Problem 87
- Complete the exercises below. When Alfred Werner was developing the field of coordination chemistry, it was argued by some that the optical activity he observed in the chiral complexes he had prepared was due to the presence of carbon atoms in the molecule. To disprove this argument, Werner synthesized a chiral complex of cobalt that had no carbon atoms in it, and he was able to resolve it into its enantiomers. Design a cobalt(III) complex that would be chiral if it could be synthesized and that contains no carbon atoms. (It may not be possible to synthesize the complex you design, but we will not worry about that for now.)
Problem 88
- Complete the exercises below. Generally speaking, for a given metal and ligand, the stability of a coordination compound is greater for the metal in the +3 oxidation state rather than in the +2 oxidation state (for metals that form stable +3 ions in the first place). Suggest an explanation, keeping in mind the Lewis acid–base nature of the metal–ligand bond.
Problem 89
Problem 91a,d
The coordination complex [Cr(CO)6] forms colorless, diamagnetic crystals that melt at 90 °C
a. What is the oxidation number of chromium in this compound?
d. Write the name for [Cr(CO)6] using the nomenclature rules for coordination compounds.
Problem 91c
The coordination complex [Cr(CO)6] forms colorless, diamagnetic crystals that melt at 90 °C
c. Given that [Cr(CO)6] is colorless, would you expect CO to be a weak-field or strong-field ligand?