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Because for tetrahedral complexes the crystal field stabilization energy is lower than pairing energy.

(b) [CoNH₃)₆]³⁺

(d) hexadentate

Option : (a) chelates

Option : (b) [Fe(CN)₆]^3-

(iv) no isomerism

(b) + 3

The oxidation state of cobalt ion in the complex [Co(NH₃)₅ Br]SO₄ is + 3.

Option : (d) hexadentate

(a) A= [Co(NH₃)₅Br]SO₄ B= [Co(NH₃)₅SO₄]Br

(b)No

Option : (d) [CO(NH₃)₆]Cl₂

(1) Cationic sphere complexes : 

A positively charged coordination sphere or a coordination compound having a positively charged coordination sphere is called cationic sphere complex.

For example :

[Zn(NH₃)₄]²⁺ and [Co(NH₃)₅Cl] SO₄ are cationic complexes. The latter has coordination sphere [Co(NH₃)₅Cl]²⁺, the anion SO₄²⁺ makes it electrically neutral.

(2) Anionic sphere complexes : 

A negatively charged coordination sphere or a coordination compound having negatively charged coordination sphere is called anionic sphere complex. 

For example, 

[Ni(CN)₄]²⁺ and K₃ [Fe(CN)₆] have anionic coordination sphere; [Fe(CN)₆]^3- and three K+ ions make the latter electrically neutral.

(3) Neutral sphere complexes : 

A neutral coordination complex does not possess cationic or anionic sphere.

[Pt(NH₃)₂Cl₂] or [Ni(CO)₄] are neither cation nor anion but are neutral sphere complexes.

In the complex, Co carries + 3 charge while 6F^- carry – 6 charge. Hence the net charge on the complex is – 3. 

Therefore it is an anionic complex.

Unpaired electrons in [Ni(H₂O₆]²⁺/d-d transition.

Detailed Answer:

[Ni(CN)₄]^2- has no unpaired electron in its d-subshell therefore d-d transition is not possible whereas [Ni(H₂O)₆]²⁺ has unpaired electron in its d-subshell resulting in d-d transition imparting colour.

The colour of a particular coordination compound depends on the magnitude of crystal field splitting energy ∆. This CFSE in turn depends on the nature of the ligand. In case of [Fe (CN)₆)^4- and [Fe(H₂O)₆]^2- the colour differs because there is a difference in the CFSE. Now, CN^- is a strong field ligand having a higher CFSE value as compared to the CFSE value of water. This means that absorption of energy for the extra d- d transition also differed. Hence, the transmitted colour also different.

In [Ni(H₂O)₆]²⁺ is a weak field ligand. Therefore there are unpaired electrons in Ni²⁺. In this complex the cl electrons from the lower energy level can be excited to the higher energy level is the possiblity of d- d transition is present. Hence [Ni(H₂O)₆]²⁺ is coloured.

In [Ni(CN)₄]^2- CN is a strong field ligand. Therefore, d- d transition is not possible due to absence of unpaired electron (CN initiates pairing of d elcctrons ). Hence it is colourless.

In [NiCl₄]^2-, due to the presence of Cl^- a weak field ligand no pairing occurs whereas in [Ni(CN)₄]^2-, CN^- is a strong field ligand and pairing takes place/diagrammatic represenlation. 

The splitting of five degenerate d-orbitals of the transition metal ion into different sets of orbitals (to_2g and e_g) having different energies in the presence of ligands in the complex is called crystal field splitting.

Crystal Field Splitting parameter (Δ₀) depends on. 

(a) Strength of the ligands and 

(b) Oxidation state of the metal.

(a) Strength of the ligands : Since strong field ligands like CN^-, en, etc. approach closer to the central metal ion, it results in a large crystal field splitting and hence Δ₀has higher values.

(b) Oxidation state of the metal : A metal ion with the higher positive charge draws the ligands closer to it which results in large separation of t_2g and e_g set of orbitals. The complexes involving metal ions with low oxidation state have low values of Δ₀. 

For example,

[Fe(NH₃)₆]³⁺ has higher Δ₀ than [Fe(NH₃)₆]²⁺. H

Crystal field splitting energy increases in the order [Cr(Cl)₆]^3– < [Cr(NH₃)₆]³⁺ < [Cr(CN)₆]^3-

The degenerate d-orbitals (in a spherical field environment) split two level i.e. e_g and t₂g in the presence of ligands. The splitting of the degenerate orbitals in the presence of ligands is called crystal field splitting and the energy difference between the two levels (e and t₂g) is called the crystal field splitting energy. It is denoted by ∆_o. After the orbitals have split, the filling of the electrons takes place. After 1 electron (each) has filled in the three t₂g orbitals, the filling of the electrons takes place in 2 ways.

It can enter the orbital (giving) rise to t³g e_g, like electronic configuration on the pairing of the electrons can take place in the t₂g orbitals (giving rise to t⁴₂g eg⁰ like electronic configuration). If the ∆_o value of a ligand is less than the pairing energy, then the electrons enter the eg orbital. On the other hand, if the ∆_o value of a ligand is more than the pairing energy, then the electrons enter the t₂g orbitals.

[Fe(CN)_6]^3– involves d²sp³ hybridisation with one unpaired electron and [Fe(H₂O)₆]³⁺ involves sp³d² hybridisation with five unpaired electrons. This difference is due to the presence of strong ligand CN– and weak ligand H₂O in these complexes.

Electronic configuration is t⁴_2g or by diagram.

When the mirror images of optical isomers of the complex are non-superimposable they are said to be chiral. 

For example, 

[Co(en)₂(NH₃)₂]³⁺.

(1) Plane polarised light : A monochromatic light having vibrations only in one plane is called a plane polarised light. This light is obtained by passing monochromatic light through NICOL prism.

(2) Optical activity : A phenomenon of rotating a plane of a plane polarised light by an optically active substance is called optical activity. This substance is said to be optically active.

(1) Optical isomerism : The phenomenon of isomerism in which different coordination compounds having same molecular formula have different optical activity is called optical isomerism.

(2) Optical isomers : Different coordination compounds having same molecular formula but different optical activity are called optical isomers.

Triamminetrichloridochromium (III)

Ligands : The neutral molecules or negatively charged anions (or rarely positive ions) which are bonded by coordinate bonds to the central metal atom or metal ion in a coordination compound are called ligands or donor groups. For example in [Cu(CN)₄]^2-, four CN^- ions are ligands coordinated to central metal ion Cu²⁺. Ligands can be classified on the basis of number of electron donor atoms in the ligand i.e. denticity.

(1) Monodentate or unidentate ligand : A ligand molecule or an ion which has only one donor atom with a lone pair of electrons forming only one coordinate bond with metal atom or ion in the complex is called monodentate or unidentate ligand. 

For example NH₃, Cl^-, OH^-, H₂O, etc.

(2) Polydentate or multidentate ligand : A ligand molecule or an ion which has two or more donor atoms with the lone pairs of electrons forming two or more coordinate bonds with the central metal atom or ion in the complex is called polydentate or multidentate ligand. For example, ethylene diamine, H₂N – (CH₂)₂ – NH₂. According to the number of donor atoms they are classified as follows :

• Bidentate ligand : This ligand has two donor atoms in the molecule or ion. For example, ethylenediamine, H₂N – (CH₂)₂ – NH₂.
• Tridentate ligand : This ligand molecule has three donor atoms or three sites of attachment.

E.g. Diethelene triamine, H₂N – CH₂ – CH₂ – NH – CH₂ – CH₂ – NH₂. This has three N donor atoms.

• Tetradentate (or quadridentate) ligand : This ligand molecule has four donor atoms. 

Eg. Triethylene tetraamine which has four N donor atoms.

• Hexdentate ligand : This ligand molecule has six donor atoms. E.g. Ethylenediamine tetracetato.

(3) Ambidentate ligand : A ligand molecule or an ion which has two or more donor atoms, however in the formation of a complex, only one donor atom is attached to the metal atom or an ion is called ambidentate ligand. For example, NO^-₂ which has two donor atoms N and O forming a coordinate bond, M ← ONO (nitrito) or M ← NO₂ (nitro). 

(4) Bridging ligand : A monodentate ligand having more than one lone pairs of electrons, hence can attach to two or more metal atoms or ions and hence acts as a bridge between different metal atoms is called bridging ligand. For example : OH^-, F^-, SO₄^-2, etc.

The neutral or negative ions bound to the central metal or ion in the coordination entity. These donate a pair/s of electrons to the central metal atom /ion. 

a) [Cu (NH₃)₄]SO₄ 

b) Tetraammine copper (ll) sulphate 

c) It is the number of ligand atoms to which the metal is directly bonded. Ligands are neutral molecules or ions bounded to the central atom/ion in the coordination entity. 

d) Oxidation number of Cu in [Cu(NH₃)₄ ]SO₄ is +2 Coordination number of Cu in [Cu(NH₃)₄ ]SO₄ is 4.

FALSE.

[Co(NO₃)(NH₃)₅]SO₄ and [Co(NO₃)(NH₃)₄ (SO₄)] (NH₃) are ionisation isomers.i.e., False.

Option : (b) -1

• The oxidation state of a metal atom or ion in the complex is the apparent charge carried by it in the complex. 
• It depends upon the atomic number and electronic configuration of the metal atom or ion. 
• The coordination number, the formula and geometry of a complex depend upon the oxidation state of the metal atom or ion. 

(a) [Fe(NH₃)₆](NO₃)₃ ⇌ [Fe(NH₃)₆]³⁺ + 3NO₃^-

NH₃ is a neutral ligand, and the charge number of complex ion is + 3. 

If the oxidation state of Fe is x then,

+ 3 = x + 6(0) 

∴ x = + 3 

∴ The oxidation state of Fe is +3.

(b) Ni(CO)₅ is a neutral complex and CO is a neutral ligand. 

If the oxidation state of Ni is x, then 

zero = x + 5 x (zero) 

∴ x = zero. 

The oxidation state of Ni is zero.

The spatial arrangement of the ligand atoms which are directly attached to the central metal atom/ion. They are commonly Octahedral, Square-planar or Tetrahedral. 

The charge that the central atom would carry if all the ligands are removed along with their pairs of electrons shared with the central atom. It is represented in parenthesis. 

In CuSO₄.5H₂O, water acts as ligand as a result it causes crystal field splitting. Hence d—d transition is possible in CuSO₄.5H₂O and shows colour. In the anhydrous CuSO₄ due to the absence of water (ligand), crystal field splitting is not possible and hence no colour.

(ii) A (4) B (3) C (2) D (1)

(ii) A (4) B (3) C (2) D (1)

(i) A (1) B (2) C (4) D (5)

(iv) A (4) B (1) C (2) D (3)

(i) A (5) B (4) C (1) D (2)

Werner’s postulates explain the bonding in coordination compounds as follows: 

(i) A metal exhibits two types of valencies ‘ namely, primary and secondary valencies. Primary valencies are satisfied by negative ions while secondary valences are satisfied by both negative and neutral ions. (In modem terminology the primary valency corresponds to the oxidation number of the metal ion, whereas the secondary valency refers to the coordination number of the metal ion) 

(ii) A metal ion has a definite number of secondary valences around the central atom. Also, these valences project in a specific direction in the space assigned to the definite geometry of the coordination compound. 

(iii) Primary valences are usually ionisable, while secondary valences are non ionisable.

1. Chlorophyll. 

2. Chelation. 

3. When a poly dentate ligand is coordinated to the metal, a ring structure is obtained, called chelate complex. Such complexes are more stable than similar complexes containing unidentate ligands.

1. EDTA → Estimation of hardness of water

2. AU(CN)₂ → Metallurgy

3. cis-platin → Cancer therapy

4. [Ag(S₂O₃)]^3- → Photography

Option : (b) 1

Option : (d) 3

Correct answer is

(c) 3

(iii) Diamminechloridonitrito-N-platinum (II)

(i) [Cr(H₂O)₆]Cl₃

(ii) Hexaaquachromium (III) chloride

(iii) Paramagnetic and high spin