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Problem 21.133
The amount of paramagnetism for a first-series transition metal complex is related approximately to its spin-only magnetic moment. The spin-only value of the magnetic moment in units of Bohr magnetons (BM) is given by sqrt(n(n + 2)), where n is the number of unpaired electrons. Calculate the spin-only value of the magnetic moment for the 2+ ions of the first-series transition metals (except Sc) in octahedral complexes with (a) weak-field ligands and (b) strong-field ligands. For which electron configurations can the magnetic moment distinguish between high-spin and low-spin electron configurations?
Problem 21.134c
Spinach contains a lot of iron but is not a good source of dietary iron because nearly all the iron is tied up in the oxalate complex [Fe(C2O4)3]3-.
(c) Draw a crystal field energy-level diagram for [Fe(C2O4)3]3-, and predict the number of unpaired electrons. (C2O42- is a weak-field bidentate ligand.)
Problem 21.134d
Spinach contains a lot of iron but is not a good source of dietary iron because nearly all the iron is tied up in the oxalate complex [Fe(C2O4)3]3-.
(d) Draw the structure of [Fe(C2O4)3]3-. Is the complex chiral or achiral?
Problem 21.136c
The percent iron in iron ore can be determined by dissolving the ore in acid, then reducing the iron to Fe2+, and finally titrating the Fe2+ with aqueous KMnO4. The reaction products are Fe2+ and Mn2+.
(c) Draw a crystal field energy-level diagram for the reactants and products, MnO4-, 3Fe1H2O2642+, 3Fe1H2O2643+, and 3Mn1H2O2642+, and predict the number of unpaired electrons for each.
Problem 21.137e
The complete reaction of 2.60 g of chromium metal with 50.00 mL of 1.200 M H2SO4 in the absence of air gave a blue solution and a colorless gas that was collected at 25°C and a pressure of 735 mm Hg. (e) When an excess of KCN is added to the solution, the color changes, and the paramagnetism of the solution
decreases. Explain.
Problem 21.138d
In acidic aqueous solution, the complex trans-[Co(en)2Cl1]2+(aq) undergoes the following substitution reaction:
trans-[Co(en)1Cl2]+(aq) + H2O(l) → trans-[Co(en)2(H2O)Cl]2+(aq) + Cl–(aq)
The reaction is first order in trans-[Co(en)2Cl2]+(aq), and the rate constant at 25°C is 3.2×10–5 s–1.
(d) Is the reaction product chiral or achiral? Explain.
Problem 21.138e
In acidic aqueous solution, the complex trans-[Co(en)2Cl1]2+(aq) undergoes the following substitution reaction:
trans-[Co(en)2Cl1]+(aq) + H2O(l) → trans-[Co(en)2(H2O)Cl]2+(aq) + Cl–(aq)
The reaction is first order in trans-[Co(en)2Cl2]+(aq), and the rate constant at 25°C is 3.2×10–5 s–1.
e. Draw a crystal field energy-level diagram for trans-[Co(en)2Cl2]+ that takes account of the fact that Cl– is a weaker-field ligand than ethylenediamine.
Problem 21.140a
Cobalt(III) trifluoroacetylacetonate, Co(tfac)3, is a sixc oordinate, octahedral metal chelate in which three planar, bidentate tfac ligands are attached to a central Co atom:
(a) Draw all possible diastereoisomers and enantiomers of Co(tfac)3.
Problem 21.140b
Cobalt(III) trifluoroacetylacetonate, Co(tfac)3, is a sixcoordinate, octahedral metal chelate in which three planar, bidentate tfac ligands are attached to a central Co atom:
(b) Diastereoisomers A and B have dipole moments of 6.5 D and 3.8 D, respectively. Which of your diastereoisomers is A and which is B?
Problem 21.140d
Cobalt(III) trifluoroacetylacetonate, Co1tfac23, is a sixcoordinate, octahedral metal chelate in which three planar, bidentate tfac ligands are attached to a central Co atom:
(d) Draw a crystal field energy-level diagram for Co1tfac23, and predict its magnetic properties. (In this complex, tfac is a strong-field ligand.)
Problem 21.2
Based on effective nuclear charge (Zeff), which ion is the strongest oxidizing agent?
(a) Cu2+
(b) Ni2+
(c) Fe2+
(d) Mn2+
Problem 21.27b
Look at the location in the periodic table of elements A, B, C, and D. What is the electron configuration of the transition metal in each of the following ions?
(a) A2+
(b) B+
Problem 21.29
The oxalate ion is a bidentate ligand as indicated in Figure 21.8. Would you expect the carbonate ion to be a monodentate or bidentate ligand? Explain your reasoning.
Problem 21.30
Classify the following ligands as monodentate, bidentate, tri-dentate, or tetradentate. Which can form chelate rings?
(a)
(b)
(c)
(d)
Problem 21.38
Predict the number of unpaired electrons for each of the following.
(c) Zn2+
(d) Cr3+
Problem 21.38b
Predict the number of unpaired electrons for each of the following.
(c) Mn3+
(d) Cr2+
Problem 21.39
Predict the number of unpaired electrons for each of the following.
(a) Sc3+
(b) Co2+
Problem 21.47
What is the general trend in standard potentials for the oxidation of first-series transition metals from Sc to Zn? What is the reason for the trend?
Problem 21.54
What is the highest oxidation state for each of the elements from Sc to Zn?
Problem 21.6
What is the name of the compound [Fe(H2O)5(SCN)]Cl2?
(a) pentaaquathiocyanatoiron(III) chloride
(b) pentaaquachlorothiocyanato iron(III)
(c) pentaaquathiocyanatoiron(III) dichloride
(d) pentaaquathiocyanatoiron(II) chloride
Problem 21.64
What is the oxidation state of the metal in each of the complexes?
a. AgCl2–
b. [Cr(H2O)5Cl]2+
c. [Co(NCS)4]2–
d. [ZrF8]4–
e. [Fe(EDTA)(H2O)]–
Problem 21.65
What is the oxidation state of the metal in each of the complexes?
a. [Ni(CN)5]3–
b. Ni(CO)4
c. [Co(en)2(H2O)Br]2+
d. [Cu(H2O)2(C2O4)2]2–
e. Co(NH3)3(NO2)3
Problem 21.76
What role does EDTA4- play as a trace additive to mayonnaise? Would the glycinate ion (H2NCH2CH2NH2) be an effective substitute for EDTA4-?
Problem 21.78a
What is the systematic name for each of the following ions?
(a) [MnCl4]2-
(b) [Ni(NH3)6]2+
Problem 21.78b
What is the systematic name for each of the following ions?
(c) [Co(CO3)3]3-
(d) [Pt(en)2(SCN)2]2+
Problem 21.79a
Assign a systematic name to each of the following ions.
(a) [AuCl4]-
(b) [Fe(CN)6]4-
Problem 21.79b
Assign a systematic name to each of the following ions.
(c) [Fe(H2O)5NCS]2+
(d) [Cr(NH3)2(C2O4)2]-
Problem 21.8
Based on the wavelength of maximum absorption of the cobalt complexes, arrange the following ligands in a spectrochemical series from weakest-field to strongest-field ligand.
(a) Cl- < NCS- < H2O < NH3
(b) Cl- < NCS- < H2O < NH3
(c) H2O < Cl- < NH3 < NCS-
(d) Cl- < H2O < NCS- < NH3
Problem 21.80
What is the systematic name for each of the following coordination compounds?
(c) [Co(NH3)4Br2]Br
(d) Cu(gly)2
Problem 21.80a
What is the systematic name for each of the following coordination compounds?
(a) Cs[FeCl4]
(b) [V(H2O)6](NO3)3