Chapter 22

Properties of Transition Elements Give the electron configuration for each of the following ions, and tell whether each is paramagnetic or diamagnetic. (a) \(\mathrm{Cr}^{3+}\) (b) \(\mathrm{V}^{2+}\) (c) \(\mathrm{Ni}^{2+}\) (d) \(\mathrm{Cu}^{+}\)

Identify two transition metal ions with the following electron configurations. (b) \([\mathrm{Ar}] 3 d^{10}\) (a) \([\mathrm{Ar}] 3 d^{6}\) (c) \([\mathrm{Ar}] 3 d^{5}\) (d) \([\mathrm{Ar}] 3 d^{8}\)

Identify an ion of a first series transition metal that is isoelectronic with each of the following. (a) \(\mathrm{Fe}^{3+}\) (b) \(\mathrm{Zn}^{2+}\) (c) \(\mathrm{Fe}^{2+}\) (d) \(\mathrm{Cr}^{3+}\)

The following equations represent various ways of obtaining transition metals from their compounds. Balance each equation. (a) \(\mathrm{Cr}_{2} \mathrm{O}_{3}(\mathrm{s})+\mathrm{Al}(\mathrm{s}) \longrightarrow \mathrm{Al}_{2} \mathrm{O}_{3}(\mathrm{s})+\mathrm{Cr}(\mathrm{s})\) (b) \(\operatorname{TiCl}_{4}(\ell)+\operatorname{Mg}(\mathrm{s}) \longrightarrow \operatorname{Ti}(\mathrm{s})+\operatorname{Mg} \mathrm{Cl}_{2}(\mathrm{s})\) (c) \(\left[\mathrm{Ag}(\mathrm{CN})_{2}\right]^{-}(\mathrm{aq})+\mathrm{Zn}(\mathrm{s}) \longrightarrow\) \(\mathrm{Ag}(\mathrm{s})+\left[\mathrm{Zn}(\mathrm{CN})_{4}\right]^{2-}(\mathrm{aq})\) (d) \(\mathrm{Mn}_{3} \mathrm{O}_{4}(\mathrm{s})+\mathrm{Al}(\mathrm{s}) \longrightarrow \mathrm{Mn}(\mathrm{s})+\mathrm{Al}_{2} \mathrm{O}_{3}(\mathrm{s})\)

Identify the products of each reaction and balance the equation. (a) \(\operatorname{CuSO}_{4}(\mathrm{aq})+\mathrm{Zn}(\mathrm{s}) \longrightarrow\) (b) \(\mathrm{Zn}(\mathrm{s})+\mathrm{HCl}(\mathrm{aq}) \longrightarrow\) (c) \(\mathrm{Fe}(\mathrm{s})+\mathrm{Cl}_{2}(\mathrm{g}) \longrightarrow\) (d) \(V(s)+O_{2}(g) \longrightarrow\)

Formulas of Coordination Compounds Which of the following ligands is expected to be monodentate and which might be polydentate? (a) \(\mathrm{CH}_{3} \mathrm{NH}_{2}\) (d) en (b) \(\mathrm{CH}_{3} \mathrm{CN}\) (e) \(\mathrm{Br}^{-}\) (c) \(\mathrm{N}_{3}^{-}\) (f) phen

One of the following nitrogen compounds or ions is not capable of serving as a ligand: \(\mathrm{NH}_{4}^{+}, \mathrm{NH}_{3}, \mathrm{NH}_{2}^{-}\) Identify this species and explain your answer.

Give the oxidation number of the metal ion in each of the following compounds. (a) \(\left[\mathrm{Mn}\left(\mathrm{NH}_{3}\right)_{6}\right] \mathrm{SO}_{4}\) (c) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}\right] \mathrm{Cl}\) (b) \(\mathrm{K}_{3}\left[\mathrm{Co}(\mathrm{CN})_{6}\right]\) (d) \(\mathrm{Cr}(\mathrm{en})_{2} \mathrm{Cl}_{2}\)

Give the oxidation number of the metal ion in each of the following complexes. (a) \(\left[\mathrm{Fe}\left(\mathrm{NH}_{3}\right)_{6}\right]^{2+}\) (c) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5}\left(\mathrm{NO}_{2}\right)\right]^{+}\) (b) \(\left[\mathrm{Zn}(\mathrm{CN})_{4}\right]^{2-}\) (d) \(\left[\mathrm{Cu}(\mathrm{en})_{2}\right]^{2+}\)

Give the formula of a complex constructed from one \(\mathrm{Ni}^{2+}\) ion, one ethylenediamine ligand, three ammonia molecules, and one water molecule. Is the complex neutral or is it charged? If charged, give the charge.

Give the formula of a complex constructed from one \(\mathrm{Cr}^{3+}\) ion, two ethylenediamine ligands, and two ammonia molecules. Is the complex neutral or is it charged? If charged, give the charge.

Naming Coordination Compounds Write formulas for the following ions or compounds. (a) dichlorobis(ethylenediamine) nickel(II) (b) potassium tetrachloroplatinate(II) (c) potassium dicyanocuprate( \(I\) ) (d) tetraamminediaquairon(II)

Write formulas for the following ions or compounds. (a) diamminetriaquahydroxochromium (II) nitrate (b) hexaammineiron(III) nitrate (c) pentacarbonyliron(0) (where the ligand is CO) (d) ammonium tetrachlorocuprate( 11 )

Name the following ions or compounds. (c) \(\left[\mathrm{Co}(\mathrm{en})_{2}\left(\mathrm{NH}_{3}\right) \mathrm{Cl}\right]^{2+}\) (a) \(\left[\mathrm{Ni}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}\right]^{2-}\) (b) \(\left[\mathrm{Co}(\mathrm{en})_{2} \mathrm{Br}_{2}\right]^{+}\) (d) \(\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{2}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)\)

Name the following ions or compounds. (a) \(\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4} \mathrm{Cl}_{2}\right]^{+}\) (c) \(\left[\mathrm{Pt}\left(\mathrm{NH}_{3}\right) \mathrm{Br}_{3}\right]^{-}\) (b) \(\operatorname{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{3} \mathrm{F}_{3}\) (d) \(\left[\mathrm{Co}(\mathrm{en})\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Cl}\right]^{2+}\)

Give the name or formula for each ion or compound, as appropriate. (a) pentaaquahydroxoiron(III) ion (b) \(\mathrm{K}_{2}\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]\) (c) \(\mathrm{K}\left[\mathrm{Cr}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}\right]\) (d) ammonium tetrachloroplatinate(II)

Give the name or formula for each ion or compound, as appropriate. (a) dichlorotetraaquachromium(III) chloride (b) \(\left[\mathrm{Cr}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{SO}_{4}\right] \mathrm{Cl}\) (c) sodium tetrachlorocobaltate( (11) (d) \(\left[\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]^{3-}\)

Draw all possible geometric isomers of the following. (a) \(\mathrm{Fe}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}\) (b) \(\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{2}(\mathrm{SCN})(\mathrm{Br})\left(\mathrm{SCN}^{-} \text {is bonded to } \mathrm{Pt}^{2+}\right.\) through S) (c) \(\operatorname{Co}\left(\mathrm{NH}_{3}\right)_{3}\left(\mathrm{NO}_{2}\right)_{3}\left(\mathrm{NO}_{2}^{-} \text {is bonded to } \mathrm{Co}^{3+} \text { through } \mathrm{N}\right)\) (d) \(\left[\mathrm{Co}(\mathrm{cn}) \mathrm{Cl}_{4}\right]^{-}\)

In which of the following complexes are geometric isomers possible? If isomers are possible, draw their structures and label them as cis or trans, or as fac or mer. (a) \(\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4} \mathrm{Cl}_{2}\right]^{+}\) (c) \(\left[\mathrm{Pt}\left(\mathrm{NH}_{3}\right) \mathrm{Br}_{3}\right]^{-}\) (b) \(\operatorname{Co}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{F}_{3}\) (d) \(\left[\mathrm{Co}(\mathrm{en})_{2}\left(\mathrm{NH}_{3}\right) \mathrm{Cl}\right]^{2+}\)

Determine whether the following complexes have a chiral metal center. (a) \(\left[\mathrm{Fe}(\mathrm{en})_{3}\right]^{2+}\) (b) trans-\(\left[\mathrm{Co}(\mathrm{en})_{2} \mathrm{Br}_{2}\right]^{+}\) (c) fac-\(\left[\mathrm{Co}(\mathrm{en})\left(\mathrm{H}_{2} \mathrm{O}\right) \mathrm{Cl}_{3}\right]\) (d) square-planar \(\mathrm{Pt}\left(\mathrm{NH}_{3}\right)\left(\mathrm{H}_{2} \mathrm{O}\right)(\mathrm{Cl})\left(\mathrm{NO}_{2}\right)\)

Four isomers are possible for \(\left[\mathrm{Co (\mathrm{en})\left(\mathrm{NH}_{3}\right)_{2}\left(\mathrm{H}_{2} \mathrm{O}\right) \mathrm{Cl}\right]^{+}\) Draw the structures of all four. (Two of the isomers are chiral, meaning that each has a non-superimposable mirror image.)

The following are low-spin complexes. Use the ligand field model to find the electron configuration of each ion. Determine which are diamagnetic. Give the number of unpaired electrons for the paramagnetic complexes. (a) \(\left[\mathrm{Mn}(\mathrm{CN})_{6}\right]^{4-}\) (c) \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\) (b) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right] \mathrm{Cl}_{3}\) (d) \(\left[\mathrm{Cr}(\mathrm{en})_{3}\right] \mathrm{SO}_{4}\)

Determine the number of unpaired electrons in the following tetrahedral complexes. All tetrahedral complexes are high spin. (a) \(\left[\mathrm{FeCl}_{4}\right]^{2-}\) (c) \(\left[\mathrm{MnCl}_{4}\right]^{2-}\) (b) \(\mathrm{Na}_{2}\left[\mathrm{CoCl}_{4}\right]\) (d) \(\left(\mathrm{NH}_{4}\right)_{2}\left[\mathrm{ZnCl}_{4}\right]\)

Determine the number of unpaired electrons in the following tetrahedral complexes. All tetrahedral complexes are high spin. (a) \(\left[\mathrm{Zn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}\right]^{2+}\) (c) \(\mathrm{Mn}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}\) (b) \(\mathrm{VOCl}_{3}\) (d) \(\left[\mathrm{Cu}(\mathrm{en})_{2}\right]^{2+}\)

For the high-spin complex \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right] \mathrm{SO}_{4},\) identify the following. (a) the coordination number of iron (b) the coordination geometry for iron (c) the oxidation number of iron (d) the number of unpaired electrons (e) whether the complex is diamagnetic or paramagnetic

For the low-spin complex \(\left[\mathrm{Co}(\mathrm{en})\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}\right] \mathrm{ClO}_{4},\) identify the following. (a) the coordination number of cobalt (b) the coordination geometry for cobalt (c) the oxidation number of cobalt (d) the number of unpaired electrons (e) whether the complex is diamagnetic or paramagnetic (f) Draw any geometric isomers.

An aqueous solution of iron(II) sulfate is paramagnetic. If \(\mathrm{NH}_{3}\) is added, the solution becomes diamagnetic. Why does the magnetism change?

In water, the titanium(III) ion, \(\left[\mathrm{Ti}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+},\) has a broad absorption band at about \(500 \mathrm{nm}\). What color light is absorbed by the ion?

In water, the chromium(II) ion, \(\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+},\) absorbs light with a wavelength of about \(700 \mathrm{nm}\). What color is the solution?

Excess silver nitrate is added to a solution containing \(1.0 \mathrm{mol}\) of \(\left[\mathrm{Co}\left(\mathrm{NH}_{9}\right)_{4} \mathrm{Cl}_{2}\right] \mathrm{Cl} .\) What amount of \(\mathrm{AgCl}\) (in moles) will precipitate?

Which of the following complexes is (are) square planar? (a) \(\left[\mathrm{Ti}(\mathrm{CN})_{4}\right]^{2-}\) (b) \(\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-}\) (c) \(\left[\mathrm{Zn}(\mathrm{CN})_{4}\right]^{2-}\) (d) \(\left[\mathrm{Pt}(\mathrm{CN})_{4}\right]^{2-}\)

Which of the following complexes containing the oxalate ion is (are) chiral? (a) \(\left[\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right) \mathrm{C}_{4}\right]^{2-}\) (b) \(\operatorname{cis}-\left[\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{2} \mathrm{Cl}_{2}\right]^{2-}\) (c) \(\operatorname{trans}-\left[\mathrm{Fe}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{2} \mathrm{Cl}_{2}\right]^{2-}\)

How many geometric isomers are possible for the square planar complex \(\left[\mathrm{Pt}\left(\mathrm{NH}_{3}\right)(\mathrm{CN}) \mathrm{Cl}_{2}\right]^{-} ?^{-}\)

A transition metal complex absorbs 425-nm light. What is its color? (a) red (c) yellow (b) green (d) blue

For the low-spin complex [Fe(en) \(\left._{2} \mathrm{Cl}_{2}\right]\) Cl, identify the following. (a) the oxidation number of iron (b) the coordination number for iron (c) the coordination geometry for iron (d) the number of unpaired electrons per metal atom (e) whether the complex is diamagnetic or paramagnetic (f) the number of geometric isomers

For the high-spin complex \(\mathrm{Mn}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2},\) identify the following. (a) the oxidation number of manganese (b) the coordination number for manganese (c) the coordination geometry for manganese (d) the number of unpaired electrons per metal atom (e) whether the complex is diamagnetic or paramagnetic (f) the number of geometric isomers

A platinum-containing compound, known as Magnus's green salt, has the formula \(\left[\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{4}\right]\left[\mathrm{PtCl}_{4}\right]\) (in which both platinum ions are \(\mathrm{Pt}^{2+}\) ). Name the cation and the anion.

Early in the 20th century, complexes sometimes were given names based on their colors. Two compounds with the formula \(\mathrm{CoCl}_{3} \cdot 4 \mathrm{NH}_{3}\) were named praseo-cobalt chloride (praseo \(=\) green ) and violio-cobalt chloride (violet color). We now know that these compounds are octahedral cobalt complexes and that they are cis and trans isomers. Draw the structures of these two compounds and name them using systematic nomenclature.

Give the formula and name of a square-planar complex of \(P_{t}^{2+}\) with one nitrite ion \(\left(N O_{2}^{-}, \text {which binds to } P_{t}^{2+}\right.\) through \(\mathrm{N}\) ), one chloride ion, and two ammonia molecules as ligands. Are isomers possible? If so, draw the structure of each isomer, and tell what type of isomerism is observed.

Give the formula of the complex formed from one \(\mathrm{Co}^{3+}\) ion, two ethylenediamine molecules, one water molecule, and one chloride ion. Is the complex neutral or charged? If charged, give the net charge on the ion.

A How many geometric isomers of the complex \(\left[\mathrm{Cr}(\mathrm{dmen})_{3}\right]^{3+}\) can exist? (dmen is the bidentate ligand 1,1-dimethylethylenediamine.) $$ \left(\mathrm{CH}_{3}\right)_{2} \ddot{\mathrm{N}} \mathrm{CH}_{2} \mathrm{CH}_{2} \ddot{\mathrm{N}} \mathrm{H}_{2} $$ 1,1-Dimethylethylenediamine, dmen

A Diethylenetriamine (dien) is capable of serving as a tridentate ligand. (equation can't copy) (a) Draw the structures of fac-Cr(dien)Cl and merCr(dien)Cl_. (b) Two different geometric isomers of mer-Cr(dien) \(\mathrm{Cl}_{2} \mathrm{Br}\) are possible. Draw the structure for each. (c) Three different geometric isomers are possible for \(\left[\mathrm{Cr}(\text { dien })_{2}\right]^{3+} .\) Two have the dien ligand in a fac configuration, and one has the ligand in a mer orientation. Draw the structure of each isomer.

From experiment we know that \(\left[\mathrm{CoF}_{6}\right]^{3-}\) is para magnetic and \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+}\) is diamagnetic. Using the ligand field model, depict the electron configuration for each ion and use this model to explain the magnetic property. What can you conclude about the effect of the ligand on the magnitude of \(\Delta_{0} ?\)

Three geometric isomers are possible for \(\left[\mathrm{Co (\mathrm{en})\left(\mathrm{NH}_{3}\right)_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}\right]^{3+} .\) One of the three is chiral; that is, it has a non-superimposable mirror image. Draw the structures of the three isomers. Which one is chiral?

The complex \(\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}\) has five unpaired electrons, whereas \(\left[\mathrm{Mn}(\mathrm{CN})_{6}\right]^{4-}\) has only one. Using the ligand field model, depict the electron configuration for each ion. What can you conclude about the effects of the different ligands on the magnitude of \(\Delta_{0} ?\)

Experiments show that \(\mathrm{K}_{4}\left[\mathrm{Cr}(\mathrm{CN})_{6}\right]\) is paramagnetic and has two unpaired electrons. The related complex \(\mathrm{K}_{4}\left[\mathrm{Cr}(\mathrm{SCN})_{6}\right]\) is paramagnetic and has four unpaired electrons. Account for the magnetism of each compound using the ligand field model. Predict where the SCN " ion occurs in the spectrochemical series relative to \(\mathrm{CN}^{-}.\)

Two different coordination compounds containing one cobalt(III) ion, five ammonia molecules, one bromide ion, and one sulfate ion exist. The dark violet form (A) gives a precipitate upon addition of aqueous \(\mathrm{BaCl}_{2}\). No reaction is seen upon addition of aqueous \(\mathrm{BaCl}_{2}\) to the violet- red form (B). Suggest structures for these two compounds, and write a chemical equation for the reaction of (A) with aqueous BaCl \(_{2}.\)

A The complex ion \(\left[\mathrm{Co}\left(\mathrm{CO}_{3}\right)_{3}\right]^{3-},\) an octahedral complex with bidentate carbonate ions as ligands, has one absorption in the visible region of the spectrum at \(640 \mathrm{nm}\). From this information: (a) Predict the color of this complex, and explain your reasoning. (b) Is the carbonate ion as weak- or strong-field ligand? (c) Predict whether \(\left[\mathrm{Co}\left(\mathrm{CO}_{3}\right)_{3}\right]^{3-}\) will be paramagnetic or diamagnetic.

The glycinate ion, \(\mathrm{H}_{2} \mathrm{NCH}_{2} \mathrm{CO}_{2}^{-},\) formed by deprotonation of the amino acid glycine, can function as a bidentate ligand, coordinating to a metal through the nitrogen of the amino group and one of the oxygen atoms. (equation can't copy) A copper complex of this ligand has the formula \(\mathrm{Cu}\left(\mathrm{H}_{2} \mathrm{NCH}_{2} \mathrm{CO}_{2}\right)_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2} .\) For this complex, determine the following. (a) the oxidation state of copper (b) the coordination number of copper (c) the number of unpaired electrons (d) whether the complex is diamagnetic or paramagnetic

Three different compounds of chromium(III) with water and chloride ion have the same composition: \(19.51 \%\) Cr, \(39.92 \%\) Cl, and \(40.57 \%\) H \(_{2}\) O. One of the compounds is violet and dissolves in water to give a complex ion with a 3+ charge and three chloride ions. All three chloride ions precipitate immediately as AgCl on adding AgNO \(_{3} .\) Draw the structure of the complex ion and name the compound. Write a net ionic equation for the reaction of this compound with silver nitrate.