Chapter 20

When degenerate d-orbitals of an isolated atom/ion are brought under the impact of magnetic field of ligands, the degeneracy is lost. The two newly formed sets of d-orbitals, depending upon nature and magnetic field of ligands are either stabilized or destabilized. The energy difference between the two sets whenever lies in the visible region of the electromagnetic spectrum, then the electronic transition \(\mathrm{t}_{2 \mathrm{~g}} \rightleftharpoons \mathrm{e}_{8}\) are responsible for colours of the co- ordination compounds \(\mathrm{Ti}^{3+}(\mathrm{aq})\) is purple while \(\mathrm{Ti}^{4+}(\mathrm{aq})\) is colourless because (a) The difference between \(\mathrm{t}_{2 \mathrm{~g}}\) and \(\mathrm{e}_{\mathrm{g}}\) of \(\mathrm{T} \mathrm{i}^{4+}\) is quite high and does not fall in visible region. (b) There is no crystal field effect in \(\mathrm{Ti}^{4+}\) (c) \(\mathrm{Ti}^{4+}\) has \(\mathrm{d}^{0}\) configuration. (d) \(\mathrm{Ti}^{4+}\) is very small ion than \(\mathrm{Ti}^{-3+}\) and does not adsorb any radiation.

When degenerate d-orbitals of an isolated atom/ion are brought under the impact of magnetic field of ligands, the degeneracy is lost. The two newly formed sets of d-orbitals, depending upon nature and magnetic field of ligands are either stabilized or destabilized. The energy difference between the two sets whenever lies in the visible region of the electromagnetic spectrum, then the electronic transition \(\mathrm{t}_{2 \mathrm{~g}} \rightleftharpoons \mathrm{e}_{8}\) are responsible for colours of the co- ordination compounds Which of the following colour is not due to d-d transition of (a) Yellow colour of CdS. (b) Red colour of blood (c) Orange colour of \(\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}\) in acidic medium. (d) Both (a) and (c)

Match the following $$ \begin{array}{ll} \hline \text { Column-I } & \text { Column-II } \\ \hline \text { (a) }\left[\mathrm{Zn}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+} & \text { (p) } \mathrm{d}^{2} \mathrm{sp}^{3} \\ \text { (b) }\left[\mathrm{Cu}(\mathrm{CN})_{4}\right]^{3-} & \text { (q) } \mathrm{sp}^{3} \\ \text { (c) }\left[\mathrm{Co}\left(\mathrm{NO}_{2}\right)_{6}\right]^{3-} & \text { (r) Number of unpaired } \\ \text { electrons is zero } \\ \text { (d) }\left[\mathrm{FeCl}_{4}\right]^{-} & \text {(s) Paramagnetic } \\\ & \text { (t) Diamangetic } \end{array} $$

Match the following Column-I Column-II \begin{tabular}{ll} Column-I & Column-II \\ \hline \(\begin{array}{ll}\text { (a) }\left[\mathrm{Co}\left(\mathrm{NO}_{2}\right)_{2}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}\left(\mathrm{NH}_{3}\right)_{2}\right] & \text { (p) } & \text { Number of } \\ \mathrm{NO}_{3} & \text { stereoisomers } \\ & =6\end{array}\) \\ \(\begin{array}{ll}\text { (b) }\left[\mathrm{Ni}(\mathrm{en})_{3}\right] \mathrm{Br}_{3} & \text { (q) Linkage } \\ \text { isomerism }\end{array}\) \\ (c) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{3}(\mathrm{py})_{3}\right] \mathrm{Br}_{2}\) & (r) Ionization isomerism \\ (d) \(\left[\mathrm{Pt}(\mathrm{en})(\mathrm{SCN})_{2}\right]\left(\mathrm{NO}_{3}\right)_{2}\) & (s) Optical isomerism \\ (t) Geometrical \\ & isomerism \\ \hline \end{tabular}

Match the following $$ \begin{array}{ll} \hline \text { Column-I (Inorganic ions) } & \text { Column-II (can } \\ & \text { get tested using } \\ & \text { reagent) } \\ \hline \text { (a) } \mathrm{Co}^{2+} & \text { (p) } \mathrm{K}_{4}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right] \\ \text { (b) } \mathrm{Cu}^{2+} & \text { (q) } \mathrm{KSCN} \\ \text { (c) } \mathrm{Fe}^{3+} & \text { (r) } \mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right] \\ \text { (d) } \mathrm{Zn}^{2+} & \text { (s) } \mathrm{KNO}_{2}+ \\ \mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H} \\ & \text { (t) } \mathrm{K}_{2}\left[\mathrm{Hg}(\mathrm{SCN})_{4}\right] \end{array} $$

Match the following $$ \begin{array}{ll} \hline \text { Column-I } & \text { Column-II } \\ \hline \begin{array}{ll} \text { (a) }\left[\mathrm{MnCl}_{6}\right]^{3-} & \text { (p) One unpaired electron } \\ \text { (b) }\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-} & \text { (q) } \mathrm{d}^{2} \mathrm{sp}^{3} \\ \text { (c) }\left[\mathrm{CoF}_{6}\right]^{3-} & \text { (r) } \mathrm{sp}^{3} \mathrm{~d}^{2} \\ \text { (d) }\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2-} & \text { (s) Four unpaired electrons } \\ & \text { (t) Three unpaired electrons } \\ \hline \end{array} \end{array} $$

Match the following $$ \begin{array}{ll} \hline \text { Column-I } & \text { Column-II } \\ \hline \text { (a) }\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-} & \text { (p) Octahedral } \\ \text { (b) }\left[\mathrm{MnF}_{6}\right]^{4-} & \text { (q) Paramagnetic } \\\ \text { (c) }\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-} & \text { (r) Square planar } \\ \text { (d) }\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+} & \text { (s) } \mathrm{d}^{2} \mathrm{sp}^{3} \text { hybridization } \\ & \text { (t) Weak field ligand. } \end{array} $$

Match the following $$ \begin{array}{ll} \text { Column-I } & \text { Column-II } \\ \hline \text { (a) } \mathrm{Na}_{2}\left[\mathrm{Pt}(\mathrm{SCN})_{4}\right] & \text { (p) Ionisation } \\ \text { (b) } \text { isomerism } \\ \text { (b) }\left[\mathrm{CrCl}_{2}\left(\mathrm{NH}_{3}\right)_{4}\right] \mathrm{NO}_{3} & \text { (q) Linkage isomerism } \\ \text { (c) }\left[\mathrm{Pt}\left(\mathrm{NO}_{2}\right)(\mathrm{gly})\right. & \text { (r) Geometrical } \\ \left.\left(\mathrm{NH}_{3}\right)\right] & \text { isomerism } \\ \text { (d) } \mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{OH})_{2}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{2}\right] & \text { (s) optical isomerism } \\ & \text { (t) hydrate isomerism } \end{array} $$

The mineral (A) is \(\left[\mathrm{CuCl}_{2} \cdot \mathrm{xCu}(\mathrm{OH})_{2}\right]\). A \(45.05 \mathrm{ml}\) solution of \(0.5089 \mathrm{M} \mathrm{HCl}\) was required to react completely with \(1.6320 \mathrm{~g}\) of the compound (A) whose molar mass is 427 . Hence, \(x\) is ___ .

14..How many milliliters of \(0.05 \mathrm{M} \mathrm{K}_{4}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]\) solution are required for titration of \(60 \mathrm{ml}\) of \(0.01\) M \(\mathrm{ZnSO}_{4}\) solution, when the product of reaction is \(\mathrm{K}_{2} \mathrm{Zn}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]_{2} ?\)

For the coordination compound \(\mathrm{PtCl}_{4} .5 \mathrm{NH}_{3}\), the charge on cation is found to be \(+3\). How many ions are furnished on ionization of the complex?

\(\mathrm{Na}_{2} \mathrm{O}\) has antifluorite structure. The coordination number of oxide ion is ____ .

The number of geomatrical isomers exhibited by \(\mathrm{Cr}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Cl}_{3}\) is _____.

Amongst the following, the total number of species which are diamagnetic is ______ . \(\mathrm{K}_{4}[\mathrm{Fe}(\mathrm{CN})], \mathrm{K}_{3}\left[\mathrm{Cr}(\mathrm{CN})_{6}\right], \mathrm{K}_{3}\left[\mathrm{Co}(\mathrm{CN})_{6}\right]\) \(\mathrm{K}_{2}\left[\mathrm{Ni}(\mathrm{CN})_{4}\right],\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+}, \mathrm{K}_{2} \mathrm{TiF}_{6}\left[\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+}\)

When excess of \(\mathrm{KCN}\) is added to aqueous solution of copper sulphate a co-ordination compound \(\mathrm{K}_{\mathrm{x}}\left[\mathrm{Cu}(\mathrm{CN})_{4}\right]\) is formed. The value of \(\mathrm{x}\) is ____ .

The number of unpaired electrons in the complex ion \(\left[\mathrm{CoF}_{6}\right]^{3-}\) is ____ .

In \(\left[\mathrm{Cr}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]^{3-}\), the isomerism shown is (a) optical (b) ionization (c) geometrical (d) ligand

A similarity between optical and geometrical isomerism is that (a) if in a compound one is present then the other will also be present (b) each gives equal number of isomers for a given compound (c) both are included in stereo isomerism (d) they have no similarity

A square planar complex is formed by hybridization of which atomic orbitals? (a) s, px, py, dx \(^{2}-y^{2}\) (b) \(s, p x, p y, d y z\) (c) \(s, p x, p y, d z^{2}\) (d) \(s, p x, p y, d x y\)

The type of isomerism present in nitropentaamine chromium (III) chloride is (a) ionization (b) optical (c) polymerization (d) linkage

In the coordination compound \(\mathrm{K}_{4}\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]\), the oxidation state of nickel is (a) \(-1\) (b) 0 (c) \(+1\) (d) \(+2\)

A mole of complex compound \(\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}_{3}\) gives 3 mole of ions, when dissolved in water. One mole of the same complex reacts with two mole of \(\mathrm{AgNO}_{3}\) solution to form two mole of \(\mathrm{AgCl}(\mathrm{s})\). The structure of the complex is (a) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Cl}_{3}\right] .2 \mathrm{NH}_{3}\) (b) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right] \cdot \mathrm{Cl}_{2}\) (c) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}\right] \mathrm{Cl} .2 \mathrm{NH}_{3}\) (d) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}\right] \mathrm{Cl}_{2} .2 \mathrm{NH}_{3}\)

Coordination compounds have great importance in biological systems. In this context, which of the following statements is incorrect? (a) chlorophylls are green pigments in plants and contain calcium (b) haemoglobin is the red pigment of blood and contains iron (c) cyanocobalamin is vitamin \(\mathrm{B}_{12}\) and contains cobalt (d) carboxypeptidase-A is an enzyme and contains zinc

Which one of the following has largest number of isomers? \(\quad\) (a) \(\left[\mathrm{Ru}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}\right]^{+}\) (b) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}\right]^{2+}\) (c) \(\left[\mathrm{Ir}\left(\mathrm{PR}_{3}\right)_{2} \mathrm{H}(\overline{\mathrm{CO}})\right]^{2+}\) (d) \(\left[\mathrm{Co}(\mathrm{en})_{2} \mathrm{Cl}_{2}\right]^{+}\) \([\mathrm{R}=\) alkyl group, en \(=\) ethylenediamine \(]\)

Which one of the following complexes is an outer orbital complex? (a) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+}\) (b) \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4}\) (c) \(\left[\mathrm{Ni}\left(\mathrm{NH}_{3}\right)_{6}\right]^{2+}\) (d) \(\left[\mathrm{Mn}(\mathrm{CN})_{6}\right]^{4}\)

The coordination number of a central metal atom in a complex is determined by (a) the number of only anionic ligands bonded to the metal ion (b) the number of ligands around a metal ion bonded pi-bonds (c) the number of ligands around a metal ion bonded by sigma and pi-bonds (d) the number of ligands around a metal ion bonded by sigma bonds

The oxidation state of \(\mathrm{Cr}\) in \(\left[\mathrm{Cr}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}\right]^{+} \quad\) (a) 0 (b) \(+1\) (c) \(+2\) (d) \(+3\)

The IUPAC name of the coordination compound \(\mathrm{K}_{3}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]\) is (a) potassium hexacyanoferrate (II) (b) potassium hexacyanoferrate (III) (c) potassium hexacyanoiron (II) (d) ripotassium acyanoiron (II)

Which of the following compounds shows optical isomerism? (a) \(\left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\right]^{2+}\) (b) \(\left[\mathrm{ZnCl}_{4}\right]^{2}\) (c) \(\left[\mathrm{Cr}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]^{3}-\) (d) \(\left[\mathrm{Co}(\mathrm{CN})_{6}\right]^{3}-\)

The value of 'spin only' magnetic moment for one of the following configurations is \(2.84 \mathrm{BM}\). The correct one is (a) \(\mathrm{d}^{4}\) (in strong ligand field) (b) \(\mathrm{d}^{4}\) (in weak ligand field) (c) \(\mathrm{d}^{3}\) (in weak as well as in strong fields) (d) \(\mathrm{d}^{5}\) (in strong ligand field)

The IUPAC name for the complex \(\left[\mathrm{Co}\left(\mathrm{NO}_{2}\right)\left(\mathrm{NH}_{3}\right)_{3}\right]\) \(\mathrm{Cl}_{2}\) is (a) nitrite-N-pentaamminecobalt(III) chloride (b) nitrite-N-pentaamminecobalt(II) chloride (c) pentaamminonitrite-N-cobalt(II) chloride (d) pentaamminonitrite-N-cobalt(III) chloride

Nickel \((\mathrm{Z}=28)\) combines with a uninegative monodentate ligand \(\mathrm{X}\) - to form a paramagnetic complex \(\left[\mathrm{Ni} \mathrm{X}_{4}\right]^{2-}\), the number of unpaired electrons in nickel and the geometry of this complex ion is (a) one, tetrahedral (b) two, tetrahedral (c) one, square planar (d) two, square planar

In \(\mathrm{Fe}(\mathrm{CO})_{5}\), the Fe-C bond possesses (a) \(\pi\)-character only (b) both \(\sigma\) and \(\pi\) characters (c) ionic character (d) \(\sigma\) character only

How many EDTA (ethylenediamine-tetraacetic acid) molecules are required to make an octahedral complex with a \(\mathrm{Ca}^{2+}\) ion? (a) six (b) three (c) one (d) two

The 'spin-only' magnetic moment [in units of Bohr magneton \(\left.\left(\mu_{\mathrm{B}}\right)\right]\) of \(\mathrm{Ni}^{2+}\) in aqueous solution would be (Atomic number of \(\mathrm{Ni}=28\) ) (a) \(2.84\) (b) \(4.90\) (c) 0 (d) \(1.73\)

Which one of the following has a square planar geometry? [2007] (a) \(\left[\mathrm{FeCl}_{4}\right]^{2-}\) (b) \(\left[\mathrm{NiCl}_{4}\right]^{2}\) (c) \(\left[\mathrm{PtCl}_{4}\right]^{2-}\) (d) \(\left[\mathrm{CoCl}_{4}\right]^{2-}\)

In which of the following octahedral complexes of Co (Atomic number 27 ), will the magnitude of \(\Delta\) be the highest? (a) \(\left[\mathrm{Co}(\mathrm{CN})_{6}\right]^{3}-\) (b) \(\left[\mathrm{Co}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]^{3}\) (c) \(\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\) (d) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+}\)

Which of the following has an optical isomer? (a) \(\left[\mathrm{CO}(\mathrm{en})\left(\mathrm{NH}_{3}\right)_{2}\right]^{2+}\) (b) \(\left[\mathrm{CO}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}(\mathrm{en})\right]^{3+}\) (c) \(\left[\mathrm{CO}(\mathrm{en})_{2}\left(\mathrm{NH}_{3}\right)_{2}\right]^{3+}\) (d) \(\left[\mathrm{CO}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Cl}\right]^{+}\)

Which of the following pairs represents linkage isomers? (a) \(\left[\mathrm{Pd}\left(\mathrm{P} \mathrm{Ph}_{3}\right)_{2}(\mathrm{NCS})_{2}\right]\) and \(\left[\mathrm{Pd}\left(\mathrm{P} \mathrm{Ph}_{3}\right)_{2}(\mathrm{SCN})_{2}\right]\) (b) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{NO}_{3}\right] \mathrm{SO}_{4}\) and \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{SO}_{4}\right] \mathrm{NO}_{3}\) (c) \(\left[\mathrm{Pt} \mathrm{Cl}_{2}\left(\mathrm{NH}_{3}\right)_{4}\right] \mathrm{Br}_{2}\) and (d) \(\left[\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}\right]\left[\mathrm{Pt} \mathrm{Cl}_{4}\right]\) and \(\left[\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{4}\right]\left[\mathrm{CuCl}_{4}\right]\)

Which one of the following has an optical isomer? [2010] (a) \(\left[\mathrm{Zn}(\mathrm{en})\left(\mathrm{NH}_{3}\right)_{2}\right]^{2+}\) (b) \(\left[\mathrm{Co}(\mathrm{en})_{3}\right]^{3+}\) (c) \(\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}(\mathrm{en})\right]^{3+}\) (d) \(\left[\mathrm{Zn}(\mathrm{en})_{2}\right]^{2+}\) (en = ethylenediamine)

A solution containing \(2.675 \mathrm{~g}\) of \(\mathrm{CoCl}_{3} \cdot 6 \mathrm{NH}_{3}\) (molar mass \(=267.5 \mathrm{~g} \mathrm{~mol}^{-1}\) ) is passed through a cation exchanger. The chloride ions obtained in solution were treated with excess of \(\mathrm{AgNO}_{3}\) to give \(4.78 \mathrm{~g}\) of \(\mathrm{AgCl}\) (molar mass \(\left.=143.5 \mathrm{~g} \mathrm{~mol}^{-1}\right) .\) The formula of the complex is (Atomic mass of \(\mathrm{Ag}=108 \mathrm{u}\) ) [2010] (a) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right] \mathrm{Cl}_{3}\) (b) \(\left[\mathrm{CoCl}_{2}\left(\mathrm{NH}_{3}\right)_{4}\right] \mathrm{Cl}\) (c) \(\left[\mathrm{CoCl}_{3}\left(\mathrm{NH}_{3}\right)_{3}\right]\) (d) \(\left[\mathrm{CoCl}\left(\mathrm{NH}_{3}\right)_{5}\right] \mathrm{Cl}_{2}\)

Which of the following facts about the complex \(\left[\mathrm{Cr}\left(\mathrm{NH}_{3}\right)_{6}\right] \mathrm{Cl}_{3}\) is wrong? (a) The complex gives white precipitate with silver nitrate solution. (b) The complex involves \(\mathrm{d}^{2} \mathrm{sp}^{3}\) hybridisation, and is octahedral in shape. (c) The complex is an outer orbital complex. (d) The complex is paramagnetic.

Which among the following will be named as dibromidobis (ethylene diamine) chromium (III) bromide? (a) \(\left[\mathrm{Cr}(\mathrm{en})_{2} \mathrm{Br}_{2}\right] \mathrm{Br}\) (b) \(\left[\mathrm{Cr}(\mathrm{en}) \mathrm{Br}_{2}\right] \mathrm{Br}\) (c) \(\left[\mathrm{Cr}(\mathrm{en})_{3}\right] \mathrm{Br}_{3}\) (d) \(\left[\mathrm{Cr}(\mathrm{en})_{2} \mathrm{Br}_{2}\right] \mathrm{Br}\)

Which of the following complex species is not expected to exihibit optical isomerism? (a) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Cl}_{3}\right]\) (b) \(\left[\mathrm{Co}(\mathrm{en})\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}\right]^{+}\) (c) \(\left[\mathrm{Co}(\mathrm{en})_{3}\right]^{3+}\) (d) \(\left[\mathrm{Co}(\mathrm{en})_{2} \mathrm{Cl}_{2}\right]^{+}\)

The pair having same magnetic movement is (a) \(\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)\right]^{2+}\) and \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}\) (b) \(\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)\right]^{2+}\) and \(\left.\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}\) (c) \(\left[\mathrm{CoCl}_{4}\right]^{2}\) and \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}\) (d) \(\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}\) and \(\left[\mathrm{CoCl}_{4}\right]^{2-}\)

Which of the following complexe shows optical isomerism (a) \(\operatorname{Cis}\left[\mathrm{Co}(\mathrm{en})_{2} \mathrm{Cl}_{2}\right] \mathrm{Cl}\) (b) \(\operatorname{trans}\left[\mathrm{Co}(\mathrm{en})_{2} \mathrm{Cl}_{2}\right] \mathrm{Cl}\) (c) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}\right] \mathrm{Cl}\) (d) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Cl}_{3}\right]\)