What is meant by stability of a coordination compound in solution? State the factors which govern stability of complexes.
Formation of a complex in solution is an equilibrium reaction. It may be represented as
The equilibrium constant of this reaction is the measure of stability of the complex. Hence the equilibrium constant is also called as stability constant or Instability constant may be defined as equilibrium constant for reverse reaction. The formation of above complex may also be written in successive steps:
Stability constant is written as
β4=K1K2K3K4.
Greater the stability constant, stronger is the metal-ligand bond.
The stability of complex will depend on
(a)nature of metal
(b)Oxidation state of metal
(c)Nature of ligand e g. chelating ligand form stabler complexes
(d)Greater the basic strength of the ligand, more will be the stability.
When 1 mol CrCl3.6H2O is treated with excess of AgNO3, 3 mol of AgCl are obtained. The formula of the complex is
Calculate the overall complex dissociation equilibrium constant for the Cu(NH3)42+ ion, given that β4 for this complex is 2.1 x 1013.
Assertion (A): [Cr(H2O)6]Cl2 and [Fe(H2O)6]Cl2 are reducing in nature. Reason (R): Unpaired electrons are present in their J-orbitals.
What is meant by unidentate didentate and ambidentate ligands? Give two examples for each.
Which of the following options are correct for [Fe(CN)6]3- complex?
(a) d2sp3 hybridisation
(b) sp3d2 hybridisation
(c) Paramagnetic
(d) Diamagnetic
On the basis of crystal field theory explain why Co(III) forms paramagnetic octahedral complex with weak field ligands whereas it forms diamagnetic octahedral complex with strong field ligands.
In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the following choices.
(a) Assertion and Reason both are true, Reason is the correct explanation of Assertion.
(b) Assertion and Reason both are true but Reason is not the correct explanation of Assertion.
(c) Assertion is true, Reason is false.
(d) Assertion is false, Reason is true.
Assertion (A): Toxic metal ions are removed by the chelating ligands. Reason (R): Chelate complexes tend to be more stable.
Match the complex species given in Column I with the possible isomerism given in Column II and assign the correct code:
Which of the following complexes show linkage isomerism?
(a) [CO(NH3)5(NO2)]2+ (b) [CO(H2O)5CO]3+
(c) [Cr(NH3)5SCN]2+ (d) [Fe(en)2Cl2]+
A complex of the type [M(AA)2X2]n+ is known to be optically active. What does this indicate about the structure of the complex? Give one example of such complex.
What is the relationship between observed colour of the complex and the wavelength of light absorbed by the complex?
Explain with two examples each of the following: coordination entity, ligand, coordination number, coordination polyhedron, homoleptic and heteroleptic.
What is crystal field splitting energy? How does the magnitude of Δ0 decide the actual configuration of d-orbitals in a coordination entity?
How many ions are produced from the complex Co(NH3)6Cl2 in solution?
(i) 6
(ii) 4
(iii)3
(iv)2
CoSO4Cl.5NH3 exists in two isomeric forms ‘A' and ‘B'. Isomer ‘A' reacts with AgNO3 to give white precipitate, but does not react with BaCl2. Isomer ‘B' gives white precipitate with BaCl2 but does not react with AgNO3. Answer the following questions.
(i) Identify A' and B' and write their structural formulas.
(ii) Name the type of isomerism involved.
(iii) Give the IUPAC name of A' and B'.
[Fe(H2O)6]3+is strongly paramagnetic whereas [Fe(CN)6]3-is weakly paramagnetic. Explain.
A coordination compound CrCl3.4H2O precipitates silver chloride when treated with silver nitrate. The molar conductance of its solution corresponds to a total of two ions. Write structural formula of the compound and name it.
Match the complex ions given in Column I with the colours given in Column II and assign the correct code:
Give the electronic configuration of the following complexes on the basis of crystal field splitting theory.
[COF6]3-, [Fe(CN)6]4- and [Cu(NH3)6]2+.
FeS04 solution mixed with (NH4)2SO4solution in 1:1 molar ratio gives the test of,Fe2+ion but CuSO4solution mixed with aqueous ammonia in 1:4 molar ratio does not give the test of Cu2+ ion. Explain why.
Match the coordination compounds given in Column I with the central metal atoms given in Column II and assign the correct code:
Why are different colours observed in octahedral and tetrahedral complexes for the same metal and same ligands?
[NiCl4]2- is paramagnetic while [Ni(CO)4] is diamagnetic though both are tetrahedraL Why?
Amongst the following ions? Which one has the highest magnetic moment value:
(i) [Cr(H2O)6]3+
(ii) [Fe(H20)6]2+ (iii) [Zn(H20)6]2+
Amongst the following, the most stable complex is:
(i) [Fe(H2O)6] (ii) [Fe(NH3)6]3+
(iii) [Fe(C2O4)3]3- (iv) [FeCl6]3-
What will be the correct order for the wavelengths of absorption in the visible region for the following:[Ni(NO2)6]4-, [Ni(NH3)6]2+, [Ni(H20)6]2+?
An aqueous pink solution of cobalt (II).chloride changes to deep biue on addition of excess of HCl. This is because
(a) [Co(H2O)6]2+ is transformed into [CoCl6]4-
(b) [CO(H2O)6]2+ is transformed into [COCl4]2-
(c) tetrahedral complexes have smaller crystal field splitting than octahedral complexes
(d) tetrahedral complexes have larger crystal field splitting than octahedral complex
Arrange following complex ions in increasing order of crystal field splitting energy (A0):
[Cr(Cl)6]3-, [Cr(CN)6]3-, [Cr(NH3)6]3+
Specify the oxidation numbers of the metals in the following coordination entities:
(i) [Co(H2O)(CN)(en)2]2+ (ii) [CoBr2(en)2]+ (iii) [PtCl4]2- (iv) K3[Fe(CN)6] (v) [Cr(NH3)3CI3]
What is the coordination entity formed when excess of aqueons KCN is added to an aqueous solution of copper sulphate? Why is it that no precipitate of copper sulphide is obtained when H2S (g) is passed through this solution?
Discuss briefly giving an example in each case the role of coordination compounds in:(i)biological systems (iii) analytical chemistry (ii)medicinal chemistry and (iv) extraction/ metallurgy of metals.
The stabilization of coordination compounds due to chelation is called the chelate effect. Which of the following is the most stable complex species?
Name the type of isomerism when ambidentate ligands are attached to central metal ion. Give two examples of ambidentate ligands.
Draw all the isomers (geometrical and optical) of
(i)[CoCl2(en)2]+
(ii)[Co(NH3) Cl (en)2]2+
(iii) [Co(NH3)2Cl2(en)]+
Aqueous copper sulphate solution (blue in colour) gives: (i) a green precipitate with aqueous potassium fluoride and (ii)a bright green solution with aqueous potassium chloride. Explain these experimental results.
Atomic number of Mn, Fe, Co and Ni are 25, 26 27 and 28 respectively. Which of the following outer orbital octahedral complexes have same number of unpaired electrons?
(a) [MnCl6]3- (b) [FeF6]3- (c) [CoF6]3- (d) [Ni(NH3)6]2+
Explain why [Fe(H2O)6]3+ has magnetic moment value of 5.92 BM whereas [Fe(CN)6]3- has a value of only 1.74 BM.
