91Ó°ÊÓ

Draw a crystal field energy-level diagram for the \(3 d\) orbitals of titanium in \(\left[\mathrm{Ti}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+} .\) Indicate the crystal field splitting, and explain why \(\left[\mathrm{Ti}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\) is colored.

The \(\left[\mathrm{Ti}(\mathrm{NCS})_{6}\right]^{3-}\) ion exhibits a single absorption band at 544 \(\mathrm{nm} .\) Calculate the crystal field splitting energy \(\Delta\) in \(\mathrm{kJ} / \mathrm{mol}\). Is NCS a stronger or weaker field ligand than water? Predict the color of \(\left[\mathrm{Ti}(\mathrm{NCS})_{6}\right]^{3-}\)

The \(\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\) ion is violet, and \(\left[\mathrm{Cr}(\mathrm{CN})_{6}\right]^{3-}\) is yellow. Ex- plain this difference using crystal field theory. Use the colors to order \(\mathrm{H}_{2} \mathrm{O}\) and \(\mathrm{CN}^{-}\) in the spectrochemical series.

For each of the following complexes, draw a crystal field energylevel diagram, assign the electrons to orbitals, and predict the number of unpaired electrons: (a) \(\left[\mathrm{CrF}_{6}\right]^{3-}\) (b) \(\left[\mathrm{V}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\) (c) \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}\)

Draw a crystal field energy-level diagram, assign the electrons to orbitals, and predict the number of unpaired electrons for each of the following: (a) \(\left[\mathrm{Cu}(\mathrm{en})_{3}\right]^{2+}\) (b) \(\left[\mathrm{FeF}_{6}\right]^{3-}\) (c) \(\left[\mathrm{Co}(\mathrm{en})_{3}\right]^{3+}\) (low-spin)

The \(\mathrm{Ni}^{2+}(a q)\) cation is green, but \(\mathrm{Zn}^{2+}(a q)\) is colorless. Explain.

The \(\mathrm{Cr}^{3+}(a q)\) cation is violet, but \(\mathrm{Y}^{3+}(a q)\) is colorless. Explain.

Weak-field ligands tend to give high-spin complexes, but strongfield ligands tend to give low-spin complexes. Explain.

Draw a crystal field energy-level diagram for a square planar complex, and explain why square planar geometry is especially common for \(d^{8}\) complexes.

For each of the following complexes, draw a crystal field energylevel diagram, assign the electrons to orbitals, and predict the number of unpaired electrons: (a) \(\left[\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+}\) (square planar) (b) \(\left[\mathrm{MnCl}_{4}\right]^{2-}\) (tetrahedral) (c) \(\left[\mathrm{Co}(\mathrm{NCS})_{4}\right]^{2-}\) (tetrahedral) (d) \(\left[\mathrm{Cu}(\mathrm{en})_{2}\right]^{2+}\) (square planar)