Coordination Compounds: Complete Concepts, Formulas and JEE Main Questions | Class 12 Chemistry
Coordination Compounds Class 12 Chemistry ka ek important chapter hai jo JEE Main mein conceptual aur direct questions ke liye useful hai. Is chapter mein central metal ion, ligands, coordination number, oxidation state, IUPAC nomenclature, isomerism, hybridisation, geometry aur magnetic properties jaise concepts cover hote hain.
Agar aap JEE Main 2027 ki preparation kar rahe ho, toh is chapter ko sirf definitions yaad karke complete nahi kar sakte. Aapko complex compounds ka charge calculate karna, unka correct naam likhna aur metal ion ki properties understand karna bhi aana chahiye. Is article mein concepts ko simple Hinglish mein examples ke saath explain kiya gaya hai.
1. Coordination Compounds Kya Hote Hain?
Coordination compound aisa compound hota hai jisme ek central metal atom ya metal ion ke around ligands coordinate bonds ke through attached hote hain.
Ligand apna lone pair central metal ko donate karta hai. Metal ion is electron pair ko accept karta hai, jisse coordinate bond form hota hai.
Example: [Co(NH₃)₆]Cl₃
Is compound ke important parts ko samjho:
- Central metal ion: Co³⁺
- Ligand: NH₃, jise ammine kaha jata hai.
- Coordination entity: [Co(NH₃)₆]³⁺
- Counter ions: 3Cl⁻
- Coordination number: 6
Yahan six NH₃ molecules cobalt ion ke saath directly attached hain. NH₃ neutral ligand hai, isliye cobalt ki oxidation state +3 hoti hai aur complex ion ka charge bhi +3 hai. Is charge ko balance karne ke liye compound mein three chloride ions present hain.
Important Terms
- Central metal ion: Metal atom ya ion jo ligands se coordinate bonds banata hai.
- Ligand: Aisa ion ya molecule jo donor atom ke through lone pair donate karta hai.
- Coordination number: Central metal se directly attached donor atoms ki total sankhya.
- Oxidation state: Complex mein metal ki formal oxidation number.
- Coordination entity: Central metal aur usse attached ligands se bana charged ya neutral unit.
JEE Trick: Coordination compound mein square brackets ke andar ka part coordination entity hota hai. Brackets ke bahar present ions counter ions ho sakte hain.
2. Types of Ligands and Coordination Number
Ligands ko unke donor atoms ki sankhya ke according monodentate, bidentate aur polydentate categories mein divide kiya ja sakta hai.
Monodentate Ligands
Monodentate ligand ek donor atom ke through central metal se attach hota hai. Isliye ek monodentate ligand generally coordination number mein 1 contribute karta hai.
Examples: NH₃, H₂O, Cl⁻ and CN⁻.
Bidentate Ligands
Bidentate ligand do donor atoms ke through same metal ion se attach ho sakta hai. Isliye ek bidentate ligand coordination number mein 2 contribute karta hai.
Example: Ethane-1,2-diamine, commonly written as en, has the formula C₂H₈N₂. Is ligand mein two nitrogen donor atoms hote hain.
Hexadentate Ligands
Hexadentate ligand six donor atoms ke through metal ion se coordinate kar sakta hai. Iska common example EDTA⁴⁻ hai.
Coordination Number Examples
| Complex | Ligand Type | Coordination Number |
|---|---|---|
| [Co(NH₃)₆]³⁺ | Six monodentate NH₃ ligands | 6 |
| [PtCl₄]²⁻ | Four monodentate Cl⁻ ligands | 4 |
| [Co(en)₃]³⁺ | Three bidentate en ligands | 6 |
| [Fe(EDTA)]⁻ | One hexadentate EDTA⁴⁻ ligand | 6 |
Most Important Exam Trick: Coordination number ligands ki count nahi, balki directly attached donor atoms ki count hoti hai.
Example: [Co(en)₃]³⁺ mein three ligands present hain, lekin har en ligand two donor atoms se attach hota hai. Isliye coordination number = 3 × 2 = 6.
3. Oxidation State and IUPAC Nomenclature
Coordination compounds mein oxidation state calculate karne ke liye complex ka overall charge aur har ligand ka charge use kiya jata hai.
Oxidation State Nikalne Ka Method
Example: [Co(NH₃)₆]Cl₃
Step 1: Complex ion ka charge identify karo.
[Co(NH₃)₆]³⁺ ka charge = +3
Step 2: Cobalt ki oxidation state ko x maan lo.
NH₃ neutral ligand hai, isliye iska charge zero hai.
Step 3: Equation banao.
x + 6(0) = +3
x = +3
Therefore, cobalt ki oxidation state +3 hai.
IUPAC Nomenclature Ke Important Rules
- Salt mein pehle cation ka naam aur uske baad anion ka naam likha jata hai.
- Complex ke andar ligands ke names alphabetical order mein likhe jate hain.
- Ligands ki sankhya batane ke liye di-, tri-, tetra-, penta- aur hexa- jaise prefixes use hote hain.
- Anionic complex mein metal ke naam ka ending generally -ate hota hai.
- Metal ki oxidation state ko Roman numerals mein parentheses ke andar likha jata hai.
- Ligand ke naam aur oxidation state ko carefully check karna chahiye.
Important Ligand Names
| Ligand | IUPAC Name Used in Complexes | Charge |
|---|---|---|
| NH₃ | Ammine | 0 |
| H₂O | Aqua | 0 |
| Cl⁻ | Chlorido | -1 |
| CN⁻ | Cyanido | -1 |
| OH⁻ | Hydroxido | -1 |
Important IUPAC Examples
- [Co(NH₃)₆]Cl₃: Hexaamminecobalt(III) chloride.
- K₄[Fe(CN)₆]: Potassium hexacyanidoferrate(II).
- [Pt(NH₃)₂Cl₂]: Diamminedichloridoplatinum(II).
Exam Tip: Naming se pehle metal ki oxidation state calculate karo. Agar complex anionic hai, toh metal ke naam mein -ate ending ko check karna mat bhoolna.
4. Isomerism in Coordination Compounds
Jab compounds ka molecular formula same ho, lekin atoms, ligands ya unki spatial arrangement different ho, toh isomerism possible hota hai.
Coordination compounds mein isomerism ko broadly structural isomerism aur stereoisomerism mein divide kiya jata hai.
A. Structural Isomerism
1. Ionisation Isomerism
Isomeric compounds solution mein different ions produce kar sakte hain because coordination sphere ke andar aur bahar present ions exchange ho jate hain.
Example: [Co(NH₃)₅Br]SO₄ and [Co(NH₃)₅SO₄]Br.
Pehle compound mein sulfate coordination sphere ke bahar hai, jabki doosre compound mein bromide coordination sphere ke bahar hai.
2. Linkage Isomerism
Kuch ligands ek se zyada donor atoms ke through metal se attach ho sakte hain. Jab same ligand different donor atoms ke through coordinate karta hai, toh linkage isomerism hota hai.
Example: NO₂⁻ ligand nitrogen atom ya oxygen atom ke through attach ho sakta hai. Nitrogen ke through attached form ko nitro aur oxygen ke through attached form ko nitrito kaha jata hai.
3. Coordination Isomerism
Coordination isomerism un compounds mein possible hota hai jahan cationic aur anionic dono complex ions present hote hain. Dono coordination spheres ke beech ligands ka distribution change ho sakta hai.
B. Stereoisomerism
1. Geometrical Isomerism
Geometrical isomerism mein ligands ki spatial positions different hoti hain. Common examples cis aur trans forms hain.
Example: [Pt(NH₃)₂Cl₂] ke cis aur trans forms hote hain.
- Cis form: Similar ligands ek doosre ke adjacent positions par hote hain.
- Trans form: Similar ligands ek doosre ke opposite positions par hote hain.
2. Optical Isomerism
Optical isomers ek doosre ke non-superimposable mirror images hote hain. Is property ko chirality se relate kiya jata hai.
Exam Trick: Isomerism identify karne ke liye pehle coordination sphere, ligand connectivity aur complex ki geometry ko dekho. Har complex geometrical ya optical isomerism show nahi karta.
5. VBT, Hybridisation and Geometry
Valence Bond Theory (VBT) coordination compounds ki bonding, hybridisation, geometry aur magnetic nature ko samajhne ka ek model hai.
Common geometries coordination number aur metal-ligand electronic interactions par depend karti hain. Coordination number 4 ke complexes tetrahedral ya square planar ho sakte hain, jabki coordination number 6 ke complexes commonly octahedral hote hain.
Coordination Number, Geometry and Hybridisation
| Coordination Number | Common Geometry | Typical Hybridisation in VBT |
|---|---|---|
| 2 | Linear | sp |
| 4 | Tetrahedral | sp³ |
| 4 | Square planar | dsp² |
| 6 | Octahedral | d²sp³ or sp³d² |
Important Examples
1. [Ni(CO)₄]
- Geometry: Tetrahedral.
- Hybridisation: sp³.
- Magnetic nature: Diamagnetic.
Diamagnetic substances mein all electrons paired hote hain.
2. [Ni(CN)₄]²⁻
- Geometry: Square planar.
- Hybridisation: dsp².
- Magnetic nature: Diamagnetic.
3. [NiCl₄]²⁻
- Geometry: Tetrahedral.
- Hybridisation: sp³.
- Magnetic nature: Paramagnetic.
Important: Coordination number alone se geometry aur magnetic nature hamesha determine nahi kar sakte. Metal ion, oxidation state, d-electron configuration aur ligand strength ko bhi consider karna hota hai.
6. Crystal Field Theory: Basic Concept
Crystal Field Theory (CFT) coordination compounds ke colour, electronic configuration aur magnetic properties ko understand karne mein useful hai.
Is theory ke according, ligands ke electric field ke kaaran central metal ion ke d-orbitals ki energies split ho sakti hain. Splitting ka pattern complex ki geometry par depend karta hai.
Octahedral Complexes
Octahedral field mein five d-orbitals do energy groups mein split hote hain:
- Lower-energy group: t₂g orbitals.
- Higher-energy group: eg orbitals.
In dono groups ke beech energy difference ko octahedral crystal field splitting energy, Δ₀, kaha jata hai.
Strong-Field and Weak-Field Ligands
Strong-field ligands generally greater d-orbital splitting produce karte hain. Weak-field ligands comparatively smaller splitting produce karte hain.
Jab splitting energy aur electron pairing energy ko compare kiya jata hai, tab complex mein electrons ke pairing behaviour aur high-spin ya low-spin configuration ka idea mil sakta hai.
JEE Main Tip: Magnetic nature determine karne ke liye unpaired electrons ki sankhya calculate karo. Diamagnetic complex mein unpaired electrons nahi hote, jabki paramagnetic complex mein ek ya zyada unpaired electrons hote hain.
7. Colour and Magnetic Properties
Colour of Coordination Compounds
Kai transition-metal coordination compounds coloured hote hain because d-orbitals ke beech electronic transitions visible light ki energy ke saath interact kar sakte hain. Absorbed light ki wavelength ke according compound ka observed colour appear hota hai.
Har coordination compound coloured nahi hota. Kuch complexes colourless bhi hote hain, depending on their electronic configuration and possible transitions.
Magnetic Properties
| Property | Electron Condition | General Behaviour |
|---|---|---|
| Diamagnetic | All electrons paired | Magnetic field se weakly repelled |
| Paramagnetic | One or more unpaired electrons | Magnetic field ki taraf attracted |
Quick Method: Pehle metal ki oxidation state find karo. Phir d-electron count determine karo. Uske baad ligand strength, geometry aur electron arrangement ko consider karke unpaired electrons count karo.
8. Solved JEE Main Question: Oxidation State and Coordination Number
Question: Find the oxidation state and coordination number of Fe in K₄[Fe(CN)₆].
Step 1: Identify the Complex Ion
Compound K₄[Fe(CN)₆] mein four K⁺ ions ka total charge +4 hai. Isliye complex ion [Fe(CN)₆]⁴⁻ ka charge -4 hoga.
Step 2: Assume the Oxidation State
Fe ki oxidation state ko x maan lo.
Har CN⁻ ligand ka charge = -1.
x + 6(-1) = -4
x - 6 = -4
x = +2
Step 3: Calculate Coordination Number
Complex ion mein six CN⁻ ligands present hain. Har CN⁻ ligand ek donor atom ke through Fe se attach hota hai.
Coordination number = 6
Final Answer
- Oxidation state of Fe = +2
- Coordination number = 6
Exam Shortcut: Neutral compound mein total positive aur negative charges ka sum zero hota hai. Is charge balance ka use karke complex ion ka charge aur phir metal ki oxidation state calculate karo.
9. Common Mistakes and Important Exam Tricks
- Coordination number: Donor atoms count karo, sirf ligand molecules nahi.
- Neutral ligands: NH₃ aur H₂O ka charge zero hota hai.
- Negative ligands: CN⁻, Cl⁻ aur OH⁻ ka charge -1 hota hai.
- Anionic complex: IUPAC naming mein metal ke naam ka -ate ending check karo.
- Magnetic nature: Unpaired electrons count karna zaroori hai.
- Strong-field ligands: Generally greater splitting promote karte hain; electron pairing ka result metal configuration aur pairing energy par bhi depend karta hai.
- Geometry: Coordination number 4 ke liye tetrahedral aur square planar dono possibilities ko consider karo.
- IUPAC nomenclature: Ligand names, alphabetical order aur oxidation state ko carefully check karo.
- Isomerism: Pehle dekho ki difference connectivity ka hai ya spatial arrangement ka.
10. Coordination Compounds Formula Sheet
| Concept | Quick Revision |
|---|---|
| Coordination compound | Central metal atom/ion + ligands |
| Coordination number | Directly attached donor atoms ki sankhya |
| Monodentate ligand | One donor atom |
| Bidentate ligand | Two donor atoms |
| Hexadentate ligand | Six donor atoms |
| NH₃ | Ammine; neutral ligand |
| H₂O | Aqua; neutral ligand |
| CN⁻ | Cyanido; charge -1 |
| Cl⁻ | Chlorido; charge -1 |
| Coordination number 4 | Tetrahedral or square planar |
| Coordination number 6 | Usually octahedral |
| Diamagnetic | No unpaired electrons |
| Paramagnetic | One or more unpaired electrons |
11. One-Minute Revision
- Coordination compound mein central metal ion ke saath ligands attached hote hain.
- Ligand lone pair donate karta hai.
- Coordination number directly attached donor atoms se calculate hota hai.
- NH₃ = ammine; H₂O = aqua; CN⁻ = cyanido; Cl⁻ = chlorido.
- Oxidation state charge-balance equation se calculate karo.
- Ligands monodentate, bidentate ya polydentate ho sakte hain.
- Isomerism ke main groups structural aur stereoisomerism hain.
- Coordination number 4 mein tetrahedral ya square planar geometry ho sakti hai.
- Coordination number 6 mein octahedral geometry common hai.
- Colour aur magnetic properties ko understand karne ke liye CFT aur electron configuration useful hain.
12. Practice Questions for JEE Main
Question 1
Find the oxidation state of Co in [Co(NH₃)₅Cl]²⁺.
Answer: Let oxidation state = x.
x + 5(0) + (-1) = +2
x = +3
Question 2
What is the coordination number of Fe in [Fe(CN)₆]⁴⁻?
Answer: 6, because six monodentate CN⁻ ligands are directly attached to Fe.
Question 3
What is the coordination number of Co in [Co(en)₃]³⁺?
Answer: 6. Each en ligand is bidentate, so 3 × 2 = 6 donor atoms.
Question 4
Which type of isomerism is shown by cis and trans forms of [Pt(NH₃)₂Cl₂]?
Answer: Geometrical isomerism.
Question 5
What is the general condition for a complex to be paramagnetic?
Answer: It has one or more unpaired electrons.
Question 6
What is the IUPAC name of [Co(NH₃)₆]Cl₃?
Answer: Hexaamminecobalt(III) chloride.
13. Download Coordination Compounds Notes PDF
Agar aap Coordination Compounds ke notes ko PDF format mein embed karna chahte ho, toh neeche diye gaye iframe mein apne hosted PDF ka direct URL add kar do. PDF ko Google Drive ya apni website par upload karke uska suitable viewing link use kar sakte ho.
14. Frequently Asked Questions (FAQs)
Q1. What is a coordination compound?
Coordination compound mein central metal atom ya ion ligands ke saath coordinate bonds banata hai.
Q2. How do you calculate coordination number?
Central metal se directly attached donor atoms count karo. Bidentate aur polydentate ligands ke multiple donor atoms ko count karna zaroori hai.
Q3. What is the difference between oxidation state and coordination number?
Oxidation state metal ka formal charge-related value hai, jabki coordination number metal se directly attached donor atoms ki sankhya hai.
Q4. What are strong-field ligands?
Strong-field ligands relatively greater crystal field splitting produce karte hain. Electron pairing aur spin state determine karne ke liye splitting energy aur pairing energy compare ki jati hain.
Q5. What is the difference between diamagnetic and paramagnetic complexes?
Diamagnetic complexes mein all electrons paired hote hain. Paramagnetic complexes mein one or more unpaired electrons present hote hain.
Q6. Is Coordination Compounds important for JEE Main?
Coordination Compounds Class 12 Chemistry ka important topic hai. Students ko nomenclature, oxidation state, coordination number, isomerism, bonding, geometry, colour aur magnetic properties ki practice karni chahiye. Exact question distribution year to year vary kar sakta hai.
Final Thoughts
Coordination Compounds chapter ko strong karne ke liye sabse pehle ligands aur coordination number ko master karo. Uske baad oxidation state aur IUPAC nomenclature ki daily practice karo. Finally, isomerism, VBT, CFT, geometry aur magnetic properties ko solved examples ke through revise karo.
JEE Main mein accuracy improve karne ka best method hai ki har complex ke liye pehle charge balance karo, phir coordination number find karo aur uske baad geometry ya magnetic nature par decide karo. Is systematic approach se calculation errors aur conceptual mistakes dono kam ho sakti hain.