Problem 4
Comment on the following observations: (a) The density of \(\mathrm{HfO}_{2}\left(9.68 \mathrm{g} \mathrm{cm}^{-3}\right)\) is much greater than that of \(\mathrm{ZrO}_{2}\left(5.73 \mathrm{g} \mathrm{cm}^{-3}\right)\) (b) \(\mathrm{NbF}_{4}\) is paramagnetic but \(\mathrm{NbCl}_{4}\) and \(\mathrm{NbBr}_{4}\) are essentially diamagnetic.
Problem 5
Suggest products in the following reactions: (a) CsBr heated with \(\mathrm{NbBr}_{5}\) at \(383 \mathrm{K} ;\) (b) \(\mathrm{KF}\) and \(\mathrm{TaF}_{5}\) melted together; (c) \(\mathrm{NbF}_{5}\) with bpy at \(298 \mathrm{K}\) (d) Comment on the structures of the group 5 metal halides in the starting materials and give possible structures for the products.
Problem 6
TaS \(_{2}\) crystallizes with a layer structure related to that of \(\mathrm{CdI}_{2},\) whereas \(\mathrm{FeS}_{2}\) adopts a distorted \(\mathrm{NaCl}\) structure. Why would you not expect \(\mathrm{TaS}_{2}\) and \(\mathrm{FeS}_{2}\) to crystallize with similar structure types?
Problem 7
Comment on the observation that \(\mathrm{K}_{3}\left[\mathrm{Cr}_{2} \mathrm{Cl}_{9}\right]\) is strongly paramagnetic but \(\mathrm{K}_{3}\left[\mathrm{W}_{2} \mathrm{Cl}_{9}\right]\) is diamagnetic.
Problem 11
Draw the structure of \(\left[\mathrm{Re}_{2} \mathrm{Cl}_{8}\right]^{2-} ;\) discuss the metal-metal bonding in the anion and its consequences on ligand orientation.
Problem 12
Suggest reasons for the variation in Re-Re bond lengths in the following species: \(\operatorname{Re} \mathrm{Cl}_{4}(273 \mathrm{pm}), \operatorname{Re}_{3} \mathrm{Cl}_{9}(249 \mathrm{pm})\) \(\left[\mathrm{Re}_{2} \mathrm{Cl}_{8}\right]^{2-}(224 \mathrm{pm}),\left[\mathrm{Re}_{2} \mathrm{Cl}_{9}\right]^{-}(270 \mathrm{pm})\) and \(\left[\mathrm{Re}_{2} \mathrm{Cl}_{4}\left(\mu-\mathrm{Ph}_{2} \mathrm{PCH}_{2} \mathrm{CH}_{2} \mathrm{PPh}_{2}\right)_{2}\right](224 \mathrm{pm})\).
Problem 13
When \(\mathrm{K}_{2}\left[\mathrm{OsCl}_{4}\right]\) is heated with \(\mathrm{NH}_{3}\) under pressure, compound \(\mathbf{A}\) of composition \(\mathrm{Os}_{2} \mathrm{Cl}_{5} \mathrm{H}_{24} \mathrm{N}_{9}\) is isolated. Treatment of a solution of A with HI precipitates a compound in which three of the five chlorines have been replaced by iodine. Treating \(1 \mathrm{mmol}\) of \(\mathrm{A}\) with \(\mathrm{KOH}\) releases \(9 \mathrm{mmol} \mathrm{NH}_{3}\). Compound \(\mathbf{A}\) is diamagnetic and none of the stronger absorption bands in the IR spectrum is Raman active. Suggest a structure for \(\mathbf{A}\) and account for the diamagnetism.
Problem 16
\(\left[\operatorname{Ir}(\mathrm{CN})_{6}\right]^{3-}\) has a regular octahedral structure. For \(\mathrm{K}_{3}\left[\mathrm{Ir}(\mathrm{CN})_{6}\right]\), the wavenumbers corresponding to the \(\mathrm{C} \equiv \mathrm{N}\) stretching modes are \(2167\left(A_{1 g}\right), 2143\left(E_{g}\right)\) and \(2130\left(T_{1 u}\right) \mathrm{cm}^{-1} \cdot(\mathrm{a})\) To which point group does \(\left[\operatorname{Ir}(\mathrm{CN})_{6}\right]^{3-}\) belong? (b) What would you observe in the IR spectrum of \(\mathrm{K}_{3}\left[\mathrm{Ir}(\mathrm{CN})_{6}\right]\) in the region between 2200 and \(2000 \mathrm{cm}^{-1} ?\)
Problem 17
When \(\mathrm{RhBr}_{3}\) in the presence of \(\mathrm{MePh}_{2}\) As is treated with \(\mathrm{H}_{3} \mathrm{PO}_{2},\) a monomeric compound \(\mathrm{X}\) is formed. \(\mathrm{X}\) contains \(2 \mathrm{Br}\) and \(3 \mathrm{MePh}_{2}\) As per \(\mathrm{Rh},\) and is a non-electrolyte. Its IR spectrum has a band at \(2073 \mathrm{cm}^{-1},\) and the corresponding band if the complex is made using \(\mathrm{D}_{3} \mathrm{PO}_{2}\) in a deuterated solvent is \(1483 \mathrm{cm}^{-1} .\) Spectrophotometric titration of \(\mathbf{X}\) with \(\mathrm{Br}_{2}\) shows that one molecule of \(\mathbf{X}\) reacts with one molecule of \(\mathrm{Br}_{2} ;\) treating the product with excess mineral acid regenerates \(\mathrm{RhBr}_{3} .\) What can you conclude about the products?
Problem 22
Comment on each of the following observations: (a) Unlike \(\left[\operatorname{Pt}\left(\mathrm{NH}_{3}\right)_{4}\right]\left[\mathrm{PtCl}_{4}\right],\left[\mathrm{Pt}\left(\mathrm{E} \mathrm{tNH}_{2}\right)_{4}\right]\left[\mathrm{PtCl}_{4}\right]\) has an electronic absorption spectrum that is the sum of those of the constituent ions. (b) AgI is readily soluble in saturated aqueous \(\mathrm{AgNO}_{3}\) but AgCl is not. (c) When \(\mathrm{Hg}\left(\mathrm{ClO}_{4}\right)_{2}\) is shaken with liquid \(\mathrm{Hg}\), the ratio \([\mathrm{Hg}(\mathrm{I})] /[\mathrm{Hg}(\mathrm{II})]\) in the resulting solution is independent of the value of \([\mathrm{Hg}(\mathrm{II})]\).
