Chapter 22

Many transition metal complexes are brightly colored. Why might the titanium( \(\mathrm{IV}\) ) compound budotitane be colorless?

Is the glucose tolerance factor that contains chromium( 111 ) paramagnetic or diamagnetic?

Coordination complexes containing paramagnetic transition metal ions make the best MRI contrast agents. a. Which of the first-row transition metal cations with a 2+ charge have the most unpaired valence electrons in the gas phase? b. Which of the first-row transition metal cations with a 2+ charge have the most unpaired valence clectrons in octahedral coordination complexes?

The complexation of mercury(II) ion with methionine $$ \mathrm{Hg}^{2+}+\text { methionine } \rightleftharpoons \mathrm{Hg} \text { (methionine) }^{2+} $$ has a formation constant of \(\log K_{f}=14.2,\) whereas the formation constant for the Hg \(^{2+}\) complex with penicillamine $$ \mathrm{Hg}^{2+}+\text { penicillamine } \rightleftharpoons \mathrm{Hg}(\text { penicillamine })^{2+} $$ is \(\log K_{f}=16.3 .\) Calculate the equilibrium constant for the reaction Hg(methionine) \(^{2+}+\) penicillamine \(\rightleftharpoons\) Hg(penicillamine) \(^{2+}+\) methionine

The complexation of mercury( 11 ) ion with cysteine in aqueous solution $$ \mathrm{Hg}^{2+}+\text { cysteinc } \rightleftharpoons \mathrm{Hg} \text { (cysteinc) }^{2+} $$ has a formation constant of \(\log K_{\mathrm{f}}=14.2,\) whereas the formation constant for the \(\mathrm{Hg}^{2+}\) complex with glycine $$ \mathrm{Hg}^{2+}+\text { glycine } \rightleftharpoons \mathrm{Hg}(\text { glycine })^{2+} $$ is \(\log K_{f}=10.3 .\) Calculate the equilibrium constant for the reaction Hg(cysteine) \(^{2+}+\) glycine \(\rightleftharpoons \mathrm{Hg}\) (glycine) \(^{2+}+\) cysteine

The equilibrium constant of the reaction \(\mathrm{CH}_{3} \mathrm{Hg}(\text { glutathione })^{+}(a q)+\) cysteinc \((a q) \rightleftharpoons\) $$ \mathrm{CH}_{3} \mathrm{Hg}(\text { cysteinc })^{+}(a q)+\text { glutathione }(a q) $$ is \(K=5.0 .\) Calculate the equilibrium concentrations of cysteine and glutathione if we start with a \(1.20 \mathrm{mM}\) solution of cysteinc and a \(1.20 \mathrm{m} M\) solution of \(\mathrm{CH}_{3} \mathrm{Hg}(\text { glutathione })^{+}\)

Lead Poisoning Children used to be treated for lead poisoning with intravenous injections of EDTA. If the concentration of EDTA in the blood of a patient is \(2.5 \times 10^{-8} \mathrm{M}\) and the formation constant for the complex \(\mathrm{Pb}(\mathrm{EDTA})^{2-}\) is \(2.0 \times 10^{18},\) what is the concentration ratio of the free (and potentially toxic) \(\mathrm{Pb}^{2+}(a q)\) in the blood to the much less toxic \(\mathrm{Pb}(\mathrm{EDTA})^{2-}\) complex?

A solid compound containing iron(II) in an octahedral crystal ficld has four unpaired clectrons at \(298 \mathrm{K}\). When the compound is cooled to \(80 \mathrm{K},\) the same sample appears to have no unpaired electrons. How do you explain this change in the compound's properties?

When \(\mathrm{Ag}_{2} \mathrm{O}\) reacts with peroxodisulfate \(\left(\mathrm{S}_{2} \mathrm{O}_{8}^{2-}\right)\) ion (a powerful oxidizing agent), \(\mathrm{AgO}\) is produced. Crystallographic and magnetic analyses of AgO suggest that it is not simply silver( 11 ) oxide, but rather a blend of silver(I) and silver(III) in a square planar environment. The \(\mathrm{Ag}^{2+}\) ion is paramagnetic but, like \(\mathrm{AgO}, \mathrm{Ag}^{+}\) and \(\mathrm{Ag}^{3+}\) are diamagnetic. Explain why.

The iron(II) compound Fe(bipy) \(_{2}(\mathrm{SCN})_{2}\) is paramagnetic, but the corresponding cyanide compound \(\mathrm{Fe}(\text { bipy })_{2}(\mathrm{CN})_{2}\) is diamagnetic. Why do these two compounds have different magnetic properties?

Aqueous solutions of copper(11)-ammonia complexes are dark blue. Will the color of the series of complexes \(\mathrm{Cu}\left(\mathrm{H}_{2} \mathrm{O}\right)_{(6-x)}\left(\mathrm{NH}_{3}\right)_{x}^{+}\) shift toward shorter or longer wavelengths as the value of \(x\) increases from 0 to \(6 ?\)

Manganese(II) chloride was one of the first compounds to be investigated as MRI contrast agents. How many unpaired electrons does the complex have when \(\mathrm{MnCl}_{2}\) dissolves in water to form the coordination compound \(\mathrm{MnCl}_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4} ?\)

Gadolinium(III) ions are used in contrast agents for MRI because they have unpaired electrons. What is the electron configuration for \(\mathrm{Gd}^{3+}\) and how many unpaired electrons does it have?