Chapter 18 Coordination Compounds

91 Coordination Compounds CHAPTER Coordination Compounds 1. The oxidation states of Cr in [Cr(H2O)6]Cl3, [Cr(C6H6)2] and K2[Cr(CN)2(O)2(O2)(NH3)] respectively are (a) +3, +4 and +6 (b) +3, +2 and +4 (c) +3, 0 and +6 (d) +3, 0 and +4 2. Consider the following reaction and statements : [Co(NH3)4Br2]+ + Br– [Co(NH3)3Br3] + NH3 (I) Two isomers are produced if the reactant complex ion is a cis-isomer. (II) Two isomers are produced if the reactant complex ion is a trans-isomer. (III) Only one isomer is produced if the reactant complex ion is a trans-isomer. (IV) Only one isomer is produced if the reactant complex ion is a cis-isomer. The correct statements are (a) (I) and (II) (b) (I) and (III) (c) (III) and (IV) (d) (II) and (IV) 3. The correct combination is (a) [Ni(CN)4]2– (b) – tetrahedral; [Ni(CO)4] – paramagnetic [NiCl4]2– – paramagnetic; [Ni(CO)4] – tetrahedral – diamagnetic; [Ni(CO)4] – square-planar [NiCl4]2– – square-planar; [Ni(CN)4]2– – paramagnetic (c) [NiCl4]2– (d) 4. 5. The total number of possible isomers for square planar [Pt(Cl)(NO2)(NO3)(SCN)]2– is (a) 16 (b) 8 (c) 24 (d) 12 The correct order of spin-only magnetic moments among the following is (Atomic number : Mn = 25, Co = 27, Ni = 28, Zn = 30) (a) [ZnCl4]2– > [NiCl4]2– > [CoCl4]2– > [MnCl4]2– (b) [CoCl4]2– > [MnCl4]2– > [NiCl4]2– > [ZnCl4]2– (c) [MnCl4]2– > [CoCl4]2– > [NiCl4]2– > [ZnCl4]2– (d) [NiCl4]2– > [CoCl4]2– > [MnCl4]2– > [ZnCl4]2– 6. Which of the following complexes will show geometrical isomerism? (a) Potassium amminetrichloroplatinate(II) (b) Aquachlorobis(ethylenediamine)cobalt(II) chloride (c) Potassium tris(oxalato)chromate(III) (d) Pentaaquachlorochromium(III) chloride 7. In Wilkinson’s catalyst, the hybridisation of central metal ion and its shape are respectively (a) dsp 2, square planar (b) sp3d, trigonal bipyramidal (c) sp3, tetrahedral (d) d2sp3, octahedral. 8. On treatment of 100 mL of 0.1 M solution of CoCl3.6H2O with excess AgNO3 , 1.2 × 1022 ions are precipitated. The complex is (a) [Co(H2O)6]Cl3 (b) [Co(H2O)5Cl]Cl2.H2O (c) [Co(H2O)4Cl2]Cl.2H2O (d) [Co(H2O)3Cl3].3H2O 9. [Co 2(CO)8] displays (a) one Co — Co bond, four bridging CO (b) one Co — Co bond, six bridging CO (c) no Co — Co bond, four bridging CO (d) no Co — Co bond, six bridging CO. terminal CO and four terminal CO and two terminal CO and four terminal CO and two 10. The pair having the same magnetic moment is [At. No.: Cr = 24, Mn = 25, Fe = 26, Co = 27] (a) [Cr(H2O)6]2+ and[CoCl4]2– (b) [Cr(H2O)6]2+ and [Fe(H2O)6]2+ (c) [Mn(H2O)6]2+ and[Cr(H2O)6]2+ (d) [CoCl4]2– and[Fe(H2O)6]2+ 11. Which one of the following complexes shows optical isomerism? (a) [Co(NH3)3Cl3] (b) cis[Co(en)2Cl2]Cl (c) trans[Co(en)2Cl2]Cl (d) [Co(NH3)4Cl 2]Cl (en = ethylenediamine) 12. Which one of the following complexes will consume more equivalents of aqueous solution of AgNO 3? (a) Na2[CrCl5(H2O)] (b) Na3[CrCl6] (c) [Cr(H2O)5Cl]Cl2 (d) [Cr(H2O)6]Cl3 13. Identify the correct trend given below : (Atomic no. : Ti = 22, Cr = 24 and Mo = 42) (a) o of [Cr(H2O)6]2+ > [Mo(H2O)6]2+ and o of [Ti(H2O)6]3+ > [Ti(H2O)6]2+ (b) o of [Cr(H2O)6]2+ > [Mo(H2O)6]2+ and o of [Ti(H2O)6]3+ < [Ti(H2O)6]2+ (c) o of [Cr(H2O)6]2+ < [Mo(H2O)6]2+ and o of [Ti(H2O)6]3+ > [Ti(H2O)6]2+ (d) o of [Cr(H2O)6]2+ < [Mo(H2O)6]2+ and o of [Ti(H2O)6]3+ < [Ti(H2O)6]2+ 14. The transition metal ions responsible for colour in ruby and emerald are, respectively (a) Co3+ and Cr3+ (b) Co 3+ and Co 3+ 3+ 3+ (c) Cr and Cr (d) Cr3+ and Co3+ 15. Which of the following is an example of homoleptic complex? (a) [Co(NH3)6]Cl3 (b) [Pt(NH3)2Cl2] (c) [Co(NH3)4Cl2] (d) [Co(NH3)5Cl]Cl2 16. Which of the following compounds is not yellow coloured? (a) (NH4)3[As(Mo3O10)4] (b) BaCrO4 (c) Zn2[Fe(CN)6] (d) K3[Co(NO2)6] 17. The number of geometric isomers that can exist for square planar [Pt(Cl)(py)(NH3)(NHOH)] + is (py = pyridine) (a) 4 (b) 6 (c) 2 (d) 3 18. The correct statement on the isomerism associated with the following complex ions, (1) [Ni(H2O)5(NH3)]2+ (2) [Ni(H2O)4(NH3)2]2+ and 2+ (3) [Ni(H2O)3(NH3)3] is (a) (1) and (2) show only geometrical isomerism (b) (1) and (2) show geometrical and optical isomerism (c) (2) and (3) show geometrical and optical isomerism (d) (2) and (3) show only geometrical isomerism. The increasing order of ligand strength of the four ligands is (a) L1 < L2 < L4 < L3 (b) L4 < L3 < L2 < L1 (c) L1 < L3 < L2 < L4 (d) L3 < L2 < L4 < L1 23. Which of the following complex species is not expected to exhibit optical isomerism? (a) [Co(en)(NH3)2Cl2]+ (b) [Co(en)3]3+ (c) [Co(en)2Cl2]+ (d) [Co(NH3)3Cl3] 24. Which among the following will be named as dibromidobis (ethylene diamine) chromium (III) bromide? (a) [Cr(en)2Br2]Br (b) [Cr(en)Br4]– (c) [Cr(en)Br2]Br (d) [Cr(en)3]Br3 25. The magnetic moment (spin only) of [NiCl4]2– is (a) 1.82 BM (b) 5.46 BM (c) 2.82 BM (d) 1.41 BM 26. Which of the following facts about the complex [Cr(NH3)6]Cl3 is wrong? (a) The complex involves d 2 sp 3 hybridisation and is octahedral in shape. (b) The complex is paramagnetic. (c) The complex is an outer orbital complex. (d) The complex gives white precipitate with silver nitrate solution. 27. Which one of the following has an optical isomer? (a) [Zn(en)2]2+ (b) [Zn(en)(NH3)2]2+ (c) [Co(en)3]3+ (d) [Co(H2O)4(en)]3+ 28. A solution contains 2.675 g of CoCl3·6NH3 (molar mass = 267.5 g mol–1) is passed through a cation exchanger. The chloride ions obtained in solution were treated with excess of AgNO3 to give 4.78 g of AgCl (molar mass = 143.5 g mol–1). The formula of the complex is (At. mass of Ag = 108 u) (a) [CoCl(NH3)5]Cl2 (b) [Co(NH3)6]Cl3 (c) [CoCl2(NH3)4]Cl (d) [CoCl3(NH3)3] 19. Which molecule/ion among the following cannot act as a ligand in complex compounds? (a) CO (b) CN– (c) CH4 (d) Br– 29. Which of the following pairs represents linkage isomers? (a) [Cu(NH3)4][PtCl4] and [Pt(NH3)4][CuCl4] (b) [Pd(PPh3)2(NCS)2] and [Pd(PPh 3)2(SCN)2] (c) [Co(NH3)5(NO3)]SO4 and [Co(NH3)5(SO4)]NO3 (d) [PtCl2(NH3)4]Br2 and [PtBr2(NH3)4]Cl2 20. When concentrated HCl is added to an aqueous solution of CoCl 2, its colour changes from reddish pink to deep blue. Which complex ion gives blue colour in this reaction? (a) [CoCl6]4– (b) [CoCl6]3– 2– (c) [CoCl4] (d) [Co(H2O)6]2+ 30. Which of the following has an optical isomer? (a) [Co(NH3)3Cl]+ (b) [Co(en)(NH3)2]2+ (c) [Co(H2O)4(en)]3+ (d) [Co(en)2(NH3)2]3+ 21. Which of the following complex ions has electrons that are symmetrically filled in both t2g and eg orbitals? (a) [CoF6]3– (b) [Co(NH3)6]2+ (c) [Mn(CN)6]4– (d) [FeF6]3– 22. The octahedral complex of a metal ion M 3+ with four monodentate ligands L1, L2, L3 and L4 absorbs wavelengths in the region of red, green, yellow and blue, respectively. 31. The coordination number and the oxidation state of the element E in the complex [E(en)2 (C2O4)]NO2 (where (en) is ethylene diamine) are, respectively (a) 6 and 3 (b) 6 and 2 (c) 4 and 2 (d) 4 and 3 32. Which of the following has a square planar geometry? (a) [PtCl4]2– (b) [CoCl4]2– (c) [FeCl4]2– (d) [NiCl4]2–. (At. nos.: Fe = 26, Co = 27, Ni = 28, Pt = 78) 33. How many EDTA (ethylenediaminetetraacetic acid) molecules are required to make an octahedral complex with a Ca2+ ion? (a) Six (b) Three (c) One (d) Two 34. In Fe(CO)5, the Fe – C bond possesses (a) -character only (b) both  and  characters (c) ionic character (d) -character only. 35. The IUPAC name for the complex [Co(NO2)(NH3)5]Cl2 is (a) nitrito-N-pentaamminecobalt(III) chloride (b) nitrito-N-pentaamminecobalt(II) chloride (c) pentaammine nitrito-N-cobalt(II) chloride (d) pentaammine nitrito-N-cobalt(III) chloride. 36. The value of the ‘spin only’ magnetic moment for one of the following configurations is 2.84 BM. The correct one is (a) d 4 ( in strong ligand field) (b) d 4 ( in weak ligand field) (c) d 3 ( in weak as well as in strong fields) (d) d 5 (in strong ligand field) 37. Which one of the following cyano complexes would exhibit the lowest value of paramagnetic behaviour? (a) [Cr(CN)6]3– (b) [Mn(CN)6]3– 3– (c) [Fe(CN)6] (d) [Co(CN)6]3– 38. Which of the following compounds shows optical isomerism? (a) [Cu(NH3)4]2+ (b) [ZnCl4]2– 3– (c) [Cr(C2O4)3] (d) [Co(CN)6]3– 39. The IUPAC name of the coordination compound K3[Fe(CN)6] is (a) potassium hexacyanoferrate (II) (b) potassium hexacyanoferrate (III) (c) potassium hexacyanoiron (II) (d) tripotassium hexacyanoiron (II) 40. The oxidation state of Cr in [Cr(NH3)4Cl2]+ is (a) +3 (b) +2 (c) +1 (d) 0 41. Which one of the following has largest number of isomers? (a) [Ru(NH3)4Cl2]+ (b) [Co(NH3)5Cl]2+ 2+ (c) [Ir(PR3)2H(CO)] (d) [Co(en)2Cl2]+ (R = alkyl group, en = ethylenediamine) 42. 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) Cyanocobalamine is B12 and contains cobalt. (d) Carboxypeptidase-A is an enzyme and contains zinc. 43. Which one of the following complexes is an outer orbital complex? (a) [Fe(CN)6]4– (b) [Mn(CN)6]4– 3+ (c) [Co(NH3)6] (d) [Ni(NH3)6]2+ [Atomic nos.: Mn = 25, Fe = 26, Co = 27, Ni = 28] 44. The coordination number of a central metal atom in a complex is determined by (a) the number of ligands around a metal ion bonded by sigma bonds (b) the number of ligands around a metal ion bonded by pibonds (c) the number of ligands around a metal ion bonded by sigma and pi-bonds both (d) the number of only anionic ligands bonded to the metal ion. 45. One mole of the complex compound Co(NH3)5Cl 3, gives 3 moles of ions on dissolution in water. One mole of the same complex reacts with two moles of AgNO3 solution to yield two moles of AgCl (s). The structure of the complex is (a) [Co(NH3)5Cl]Cl2 (b) [Co(NH3)3Cl2]·2NH3 (c) [Co(NH3)4Cl2]Cl·NH3 (d) [Co(NH3)4Cl]Cl2·NH3 46. Ammonia forms the complex ion [Cu(NH3)4]2+ with copper ions in alkaline solutions but not in acidic solutions. What is the reason for it? (a) In acidic solutions hydration protects copper ions. (b) In acidic solutions protons coordinate with ammonia molecules forming NH4+ ions and NH3 molecules are not available. (c) In alkaline solutions insoluble Cu(OH)2 is precipitated which is soluble in excess of any alkali. (d) Copper hydroxide is an amphoteric substance. 47. In the coordination compound, K4[Ni(CN)4], the oxidation state of nickel is (a) –1 (b) 0 (c) +1 (d) +2 48. The type of isomerism present in nitropentamine chromium (III) chloride is (a) optical (b) linkage (c) ionization (d) polymerisation. 49. CH3 – Mg – Br is an organometallic compound due to (a) Mg – Br bond (b) C – Mg bond (c) C – Br bond (d) C – H bond. ANSWER KEY 1. 13. 25. 37. 49. (c) (c) (c) (d) (b) 2. 14. 26. 38. (b) (c) (c) (c) 3. 15. 27. 39. (b) (a) (c) (b) 4. 16. 28. 40. (d) (c) (b) (a) 5. 17. 29. 41. (c) (d) (b) (d) 6. 18. 30. 42. (b) (d) (d) (a) 7. 19. 31. 43. (a) (c) (a) (d) 8. 20. 32. 44. (b) (c) (a) (a) 9. 21. 33. 45. (b) (d) (c) (a) 10. 22. 34. 46. (b) (c) (b) (b) 11. 23. 35. 47. (b) (d) (d) (b) 12. 24. 36. 48. (d) (a) (a) (b) 1. (c) : [Cr(H2O)6]Cl3 : x + 6 × 0 + 3 × –1 = 0  x = +3 [Cr(C6H6)2] : x + 2 × 0  x = 0 K2[Cr(CN)2(O)2(O2) (NH3)] : 2 × (+1) + x + 2 × (–1) + 2 × (–2) + 2 × (–1) + 0 = 0 2 + x – 2 – 4 – 2 = 0  x = +6 2. (b) : Br H3N + H3N Br Br +Br –NH 3 Co H3N Co H3N Br NH3 cis-isomer Br H3N +Br –NH 3 3d NH3 4s Cl – is a weak field ligand and cannot take part in pairing of electrons. [NiCl4]2–: [Ar] 3d Cl– Cl– Cl – Cl – sp 3 hybridisation Hence, the complex is tetrahedral and paramagnetic with two unpaired electrons. [Ni(CN)4]2– : Oxidation state of Ni is [Ni(CN)4]2– = + 2 CN– is a strong field ligand, thus pairing of electrons takes place in d-orbitals. [Ni(CN)4] 2– : [Ar] 4p 4s CN – O3N SCN ( cis-form) 5. (c) : Spin-only magnetic moment ()  n(n  2) B.M. Where, n is the number of unpaired electron(s). As Cl– is a weak field ligand, no pairing of electrons takes place. (i) [ZnCl4]2– : Zn 2+ : [Ar]3d10 [ZnCl4]2– : 3d 4p 4s CN – CN sp3 hybridization n = 0,   = 0 (ii) [NiCl4]2– : Ni2+ : [Ar]3d8 [NiCl4]2– : 3d 4p 4s sp3 hybridization n = 2,    2(2  2) = 2.83 B.M. (iii) [CoCl4]2– : – CN – dsp 2 hybridisation Hence, the complex is square planar and diamagnetic. [Ni(CO)4] : Oxidation state of Ni in [Ni(CO)4] is zero. CO is a strong field ligand. 4s 3d Ni : [Ar] 3d NO3 4p 4s 3d (cis-form) M All four linkage isomers give three geometrical isomers each. Thus, total 12 isomers are possible. (b) : [NiCl4]2– : Oxidation state of Ni in [NiCl4]2– = + 2 Ni2+ : [Ar] SCN (trans-form) mer-isomer 3. NO2 SCN Br NH3 M M Co Br 4. (d) : [Pt(Cl)(NO2)(NO3)(SCN)]2– : This complex will show linkage isomerism as –NO 2 and –SCN are bidentate ligand. These are : [Pt(Cl)(NO2)(NO3)(NCS)] 2– [Pt(Cl)(ONO)(NO3)(NCS)] 2– [Pt(Cl)(ONO)(NO3)(SCN)] 2– [Pt(Cl)(NO2)(NO3)(SCN)]2– It exhibits geometrical isomerism also Cl Cl Cl NO3 NO2 NO2 Br NH3 fac-isomer NH3 Hence, the complex is tetrahedral and diamagnetic. 4s 4p CO CO CO CO [Ni(CO)4] : [Ar] sp3 hybridisation Co2+ : [Ar]3d7 [CoCl4]2– : 3d 4p 4s sp3 hybridization n = 3,    3(3  2) = 3.87 B.M. (iv) [MnCl4]2– : Mn2+ : [Ar]3d5 [MnCl4]2– : 3d n = 5,    5(5  2) = 5.91 B.M. 4s 4p sp3 hybridization 6. (b) : (a) K[Pt(NH3)Cl3] : This complex is [MAB3] type, which does not show geometrical isomerism. (b) [Co(H 2O)Cl (en) 2]Cl : This complex shows geometrical isomerism. OH2 + + en OH2 en en Co Co Cl en 4d 5p 5s [Kr] Cl– PPh3 PPh3 PPh3 dsp2 hybridization Thus, complex is square planar. (b) : Number of moles of complex  M V(mL) 1000 0.1  100   0.01 1000 Moles of ions precipitated with excess of AgNO3 1.2  1022  0.01992  0.02 6.022  1023 Now, number of Cl– ions present in ionisation sphere Moles of ions precipitated with excess AgNO3 0.02   2 Moles of complex 0.01 Hence, the formula of complex is [Co(H2O)5Cl]Cl2·H2O. 9. CO OC CO OC — Co — Co — CO (b) : OC CO CO 10. (b) : [Cr(H2O)6]2+ : Cr2+  [Ar]3d44s0 3d 4s 5 unpaired electrons Hence, [Cr(H 2O) 6] 2+ and [Fe(H 2O) 6] 2+ have same number of unpaired electrons i.e., same magnetic moment. 11. (b) : [Co(NH3)3Cl 3] has two geometrical isomers but both are optically inactive due to plane of symmetry. cis[Co(en)2Cl 2]Cl is optically active. trans-isomer (c) K3[Cr(ox)3] : This complex is [M(AA)3] type, it does not show geometrical isomerism. (d) [Cr(H2O)5Cl] Cl2 : This complex is [MA5B] type. It does not show geometrical isomerism. 7. (a) : Wilkinson’s catalyst is [RhCl(PPh3)3]. Oxidation state of Rh in [RhCl(PPh3)3] = +1 Electronic configuration of Rh = [Kr]4d 85s1 Electronic configuration of Rh + = [Kr]4d 8 As Rh(4d) always forms low spin complex, Hence, [RhCl(PPh 3)3] :  3d Cl cis-isomer 8. [Mn(H2O)6]2+ : Mn2+  [Ar]3d54s0 4s trans[Co(en)2Cl2]Cl is optically inactive due to plane of symmetry. [Co(NH3)4Cl2]Cl has two geometrical isomers but both are optically inactive due to plane of symmetry. 12. (d) : Chloride ions outside the coordination sphere are ionisable only. Hence, [Cr(H2O)6]Cl3 will give 3 Cl– ions in aqueous solution which consume more equivalents of AgNO3. 13. (c) :  o increases from 3d-series to 4d-series. Thus, [Cr(H2O)6]2+ has lower o value than that of [Mo(H2O)6]2+. Also, for a metal ion having lesser number of d-electrons, o value increases. Thus, [Ti(H2O)6]3+ has greater o value than that of [Ti(H2O)6]2+. 14. (c) : Red colour of ruby (Al2O3) arises due to Cr3+ replaces Al3+ ions in octahedral sites. Green colour of emerald (Be3Al2(SiO3)6) arises due to Cr3+ replaces Al3+ ions in octahedral sites. 15. (a) : Homoleptic complexes have only one type of ligands. In complex [Co(NH3)6]Cl3, NH3 serves as the only ligand. 16. (c) : Zn 2[Fe(CN)6] is bluish white while all others are yellow coloured. 17. (d) : The number of geometrical isomers for square planar are 3. 18. (d) : Octahedral complexes of the type Ma 4b2 and Ma3b 3 exhibit geometrical isomerism only. Geometrical isomers : 2+ 2+ NH3 NH3 H3N H2O OH2 OH2 Ni H2O OH2 Ni OH2 H2O cis-form 4 unpaired electrons [CoCl4]2– : Co 2+  [Ar]3d74s0 3d 4s H3N [Fe(H2O)6]2+ : Fe2+  [Ar]3d64s0 4 unpaired electrons 4s H2O OH2 cis-form OH2 trans-form [Ni(H2O)4(NH3)2]2+ 2+ OH2 H2O Ni 3 unpaired electrons 3d NH3 NH3 NH3 2+ OH2 Ni OH2 H2O NH3 OH2 trans-form [Ni(H2O)4(NH3)2]2+ 19. (c) : Ligand donates electron to metal. In methane there is no electron to donate, it is stable with complete octet. 20. (c) : [Co(H2O)6]2+ + 4Cl– [CoCl4]2– + 6H2O Pink Blue 21. (d) : [CoF6]3– : Co 3+ : 3d6, F– is a weak field ligand. t42g eg2 [Co(NH3)6]2+ : Co 2+ : 3d7, NH3 is a strong field ligand. t62g e1g [Mn(CN)6]4– : Mn2+ : 3d5, CN– is a strong field ligand. t52g e0g [FeF6]3– : Fe3+ : 3d5, F – is a weak field ligand. t32g eg2 22. (c) : V I B G Y O R Wavelength increasing ( ) en en According to the spectrochemical series, more the absorption frequency, stronger is the ligand. 1 or,  or CFSE  Strength of ligands   Hence, the increasing order of ligand strength is, L1 < L3 < L2 < L4 (Red) (Yellow) (Green) (Blue) 23. (d) : [Co(NH3)3Cl 3] will not exhibit optical isomerism due to presence of plane of symmetry. 24. (a) 25. (c) : In the paramagnetic and tetrahedral complex [NiCl4]2–, the nickel is in +2 oxidation state and the ion has the electronic configuration 3d 8. The hybridisation scheme is as shown in figure. Ni 2+, [Ar]3d8 : NH3 H 3N 3+ Co3+ Co H3N NH3 en en Non-superimposable mirror images 31. (a) : In the given complex [E(en)2(C2O4)]+NO2– ethylene diamine is a bidentate ligand and (C2O42–) oxalate ion is also bidentate ligand. Therefore co-ordination number of the complex is 6 i.e., it is an octahedral complex. Oxidation number of E in the given complex is x + 2 × 0 + 1 × (–2) = +1  x = 3 32. (a) : In 4-coordinate complexes Pt, the four ligands are arranged about the central 2-valent platinum ion in a square planar configuration. [NiCl4]2– :  In[Pd(PPh3)2(NCS)2], the linkage of NCS and Pd is through N. In [Pd(PPh3)2(SCN)2], the linkage of SCN and Pd is through S. 30. (d) : Optical isomerism is usually exhibited by octahedral compounds of the type [M(AA)2B2], where (AA) is a symmetrical bidentate ligand. Square planar complexes rarely show optical isomerism on accout of presence of axis of symmetry. Thus among the given options, [Co(en)2(NH3)2]3+ exhibits optical isomerism. n( n  2) BM  (2(2  2)  8 = 2.82 BM 26. (c) : The complex [Cr(NH3)6]Cl3 involves d2sp3 hybridization as it involves (n – 1)d orbitals for hybridization. It is an inner orbital complex. 27. (c) : Optical isomers rarely occur in square planar complexes due to the presence of axis of symmetry. Optical isomerism is common in octahedral complexes of the general formula, [Ma 2 b 2 c 2 ] n± , [Mabcdef] n± , [M(AA) 3 ] n± , [M(AA)2a2]n±, [M(AA)2ab]n± and [M(AB)3]n±. Thus, among the given options, only [Co(en)3]3+ shows optical isomerism. 33. (c) : EDTA, which has four donor oxygen atoms and two donor nitrogen atoms in each molecule forms complex with Ca2+ ion. The free acid H4EDTA is insoluble and the disodium salt Na2H2EDTA is the most used reagent. Ca2+ + [H2EDTA]2–  [Ca(EDTA)]2– + 2H+ 34. (b) : In a metal carbonyl, the metal carbon bond possesses both the - and -character. A -bond between metal and carbon atom is formed when a vacant hybrid bond of the metal atom overlaps with an orbital of C atom of carbon monoxide containing a lone pair of electrons. Formation of -bond is caused when a filled orbital of the metal atom overlaps with a vacant antibonding * orbital of C atom of CO. This overlap is also called back donation of electrons by metal atom to carbon. – M + + + C M O C O (a) 28. (b) : No. of moles of CoCl3·6NH3  2.675  0.01 267.5 4.78  0.03 143.5 Since 0.01 moles of the complex CoCl3·6NH3 gives 0.03 moles of AgCl on treatment with AgNO3, it implies that 3 chloride ions are ionisable, in the complex. Thus, the formula of the complex is [Co(NH3)6]Cl3. 29. (b) : Linkage isomerism is exhibited by compounds containing ambidentate ligand. No. of moles of AgCl  + – + M + – .. C O.. – – + – M + O.. C (b) – + (a) The formation of the metal  carbon -bond using an unshared pair of the C atom. (b) The formation of the metal  carbon -bond. The -overlap is perpendicular to the nodal plane of -bond. 35. (d) : [Co(NO2)(NH3)5]Cl2 : Pentaaminenitrito-N-cobalt(III) chloride 36. (a) : Spin only magnetic moment  n(n  2) B.M. Where n = no. of unpaired electron. 39. (b) : K3[Fe(CN)6] : Potassium hexacyanoferrate(III) Given, n(n  2)  2.84 or, n (n + 2) = 8.0656  n = 2 In an octahedral complex, for a d 4 configuration in a strong field ligand, number of unpaired electrons = 2 41. (d) : [Co(en)2Cl 2] + shows geometrical as well as optical isomerism. 37. (d) : [Co(CN)6]3– Co  [Ar] 3d7 4s2 Co3+  [Ar] 3d6 4s0 3d 4p 4s In presence of strong field ligand CN– pairing of electrons takes place. ×× ×× ×× ×× ×× ××   d2sp3 There is no unpaired electron, so the lowest value of paramagnetic behaviour is observed. 38. (c) : Optical isomers rarely occur in square planar complexes on account of the presence of axis of symmetry. Optical isomerism is very common in octahedral complexes having general formulae: [Ma2b2c2]n±, [Mabcdef]n±, [M(AA)3]n±, [M(AA)2a2]n±, [M(AA)2ab]n± and [M(AB)3]n± (where AA = symmetrical bidentate ligand and AB = unsymmetrical bidentate ligand). ox ox 3– 3– ox Cr Cr ox ox ox 40. (a) : Let the oxidation state of Cr in [Cr(NH3)4Cl2]+ = x x + 4(0) + 2(–1) = +1  x – 2 = +1  x = +1 + 2 = +3 42. (a) : Chlorophyll are green pigments in plants and contains magnesium instead of calcium. 43. (d) : Complex ion [Fe(CN)6]4– [Mn(CN)6]4– [Co(NH3)6]3+ [Ni(NH3)6]2+ Hybridization of central ion d 2sp3 (inner) d 2sp3 (inner) d 2sp3 (inner) sp3d 2 (outer) 44. (a) : The number of atoms of the ligands that are directly bound to the central metal atom or ion by coordinate bonds is known as the coordination number of the metal atom or ion. Coordination number of metal = number of  bonds formed by metal with ligands. 45. (a) : Given reactions can be explained as follows: [Co(NH3)5Cl]2+ + 2Cl–  3 ions. [Co(NH3)5Cl]Cl2 [Co(NH3)5Cl]Cl2 + 2AgNO3  [Co(NH3)5Cl](NO3)2 + 2AgCl 46. (b) : In acidic solution, NH3 forms a bond with H+ to give NH4+ ion which does not have a lone pair on N atom. Hence it cannot act as a ligand. 47. (b) : Let the oxidation number of Ni in K4 [Ni(CN)4 ] = x 1 × 4 + x × (–1) × 4 = 0  4 + x – 4 = 0  x = 0 48. (b) : The nitro group can attach to metal through nitrogen as (–NO2) or through oxygen as nitrito (–ONO). 49. (b) : Compounds that contain at least one carbon-metal bond are called organometallic compounds.