Problem 2
The absorption spectrum of \(\left[\mathrm{Ti}\left(\mathrm{OH}_{2}\right)_{6}\right]^{3+}\) exhibits a band with \(\lambda_{\max }=510 \mathrm{nm} .\) What colour of light is absorbed and what colour will aqueous solutions of \(\left[\mathrm{Ti}\left(\mathrm{OH}_{2}\right)_{6}\right]^{3+}\) appear?
Problem 4
Arrange the following ligands in order of increasing field strength: \(\mathrm{Br}^{-}, \mathrm{F}^{-},[\mathrm{CN}]^{-}, \mathrm{NH}_{3},[\mathrm{OH}]^{-}, \mathrm{H}_{2} \mathrm{O}\).
Problem 5
For which member of the following pairs of complexes would \(\Delta_{\text {oct }}\) be the larger and why: (a) \(\left[\mathrm{Cr}\left(\mathrm{OH}_{2}\right)_{6}\right]^{2+}\) and \(\left[\mathrm{Cr}\left(\mathrm{OH}_{2}\right)_{6}\right]^{3+} ;(\mathrm{b})\left[\mathrm{CrF}_{6}\right]^{3-}\) and \(\left[\mathrm{Cr}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+}\) (c) \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-}\) and \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-} ;(\mathrm{d})\left[\mathrm{Ni}\left(\mathrm{OH}_{2}\right)_{6}\right]^{2+}\) and \(\left[\mathrm{Ni}(\mathrm{en})_{3}\right]^{2+} ;(\mathrm{c})\left[\mathrm{MnF}_{6}\right]^{2-}\) and \(\left[\mathrm{ReF}_{6}\right]^{2-} ;(\mathrm{f})\left[\mathrm{Co}(\mathrm{cn})_{3}\right]^{3+}\) and \(\left[\mathrm{Rh}(\mathrm{en})_{3}\right]^{3+} ?\)
Problem 10
(a) What do you understand by the nephelauxetic effect? (b) Place the following ligands in order of increasing nephelauxetic effect: \(\mathrm{H}_{2} \mathrm{O}, \mathrm{I}^{-}, \mathrm{F}^{-}, \mathrm{en},[\mathrm{CN}]^{-}\) \(\mathrm{NH}_{3}\).
Problem 11
Discuss each of the following observations: (a) The \(\left[\mathrm{CoCl}_{4}\right]^{2-}\) ion is a regular tetrahedron but \(\left[\mathrm{CuCl}_{4}\right]^{2-}\) has a flattened tetrahedral structure. (b) The electronic spectrum of \(\left[\mathrm{CoF}_{6}\right]^{3-}\) contains two bands with maxima at 11500 and \(14500 \mathrm{cm}^{-1}\).
Problem 12
The \(3 p^{2}\) configuration of an Si atom gives rise to the following terms: \(^{1} S_{0} .^{3} P_{2},^{3} P_{1},^{3} P_{0}\) and \(^{1} D_{2} .\) Use Hund's rules to predict the relative cnergies of these terms, giving an explanation for your answer.
Problem 21
Comment on the following statements concerning electronic spectra. (a) \(\left[\mathrm{OsCl}_{6}\right]^{3-}\) and \(\left[\mathrm{RuCl}_{6}\right]^{3-}\) exhibit LMCT bands at 282 and \(348 \mathrm{nm},\) respectively. (b) \(\left[\mathrm{Fe}(\mathrm{bpy})_{3}\right]^{2+}\) is expected to exhibit an MLCT rather than an LMCT absorption.
Problem 22
Rationalize why the absorption spectrum of an aqueous solution of \(\left[\mathrm{Ti}\left(\mathrm{OH}_{2}\right)_{6}\right]^{2+}\) (stable under acidic conditions) cxhibits two well-separated bands \((430 \text { and } 650 \mathrm{nm})\) assigned to "d-d' transitions, whereas that of an aqueous solution of \(\left[\mathrm{Ti}\left(\mathrm{OH}_{2}\right)_{6}\right]^{3+}\) consists of one absorption \(\left(\lambda_{\max }=490 \mathrm{nm}\right)\) with a shoulder \((580 \mathrm{nm})\).
Problem 25
Values of the Racah parameter \(B\) for free gaseous \(\mathrm{Cr}^{3+}\) \(\mathrm{Mn}^{2+}\) and \(\mathrm{Ni}^{2+}\) ions are 918,960 and \(1041 \mathrm{cm}^{-1}\) respectively. For the corresponding hexaaqua ions, values of \(B\) are 725,835 and \(940 \mathrm{cm}^{-1} .\) Suggest a reason for the reduction in \(B\) on forming each complex ion.
Problem 27
Explain why in high-spin octahedral complexes, orbital contributions to the magnetic moment are only important for \(d^{1}, d^{2}, d^{6}\) and \(d^{7}\) configurations.
