Consider the following low-spin complexes K_3[Co(NO_2)_6]$K_{3}[Co(NO_{2})_{6}]$, K_4[Fe(CN)_6]$K_{4}[Fe(CN)_{6}]$, K_3[Fe(CN)_6]$K_{3}[Fe(CN)_{6}]$, Cu_2[Fe(CN)_6]$Cu_{2}[Fe(CN)_{6}]$ and Zn_2[Fe(CN)_6]$Zn_{2}[Fe(CN)_{6}]$. The sum of the spin-only magnetic moment values of complexes having yellow colour is ________ B.M. (answer is nearest integer)

### Core Logic Let us identify the central metal atom/element present in each of the given coordination complexes or biological molecules: 1. **Ziegler-Natta catalyst**: Used for polymerization of alkenes. Its chemical composition involves TiCl_4$TiCl_4$ and (C_2H_5)_3Al$(C_2H_5)_3Al$. Hence, the transition metal present is Titanium (IV). 2. **Blood pigment (Haemoglobin)**: The oxygen-carrying metalloprotein in red blood cells. It contains an Iron (III) central atom coordinated to a porphyrin ring. 3. **Wilkinson's catalyst**: Used for the hydrogenation of alkenes. Its formula is [RhCl(PPh_3)_3]$[RhCl(PPh_3)_3]$, meaning it contains Rhodium (I). 4. **Vitamin B_12$B_{12}$ (Cyanocobalamin)**: A biologically important coordination compound containing Cobalt (II) at the center of a corrin ring. ### Step 1: Final Mapping Matching the elements: (A) Ziegler catalyst rightarrow$\rightarrow$ (IV) Titanium (B) Blood Pigment rightarrow$\rightarrow$ (III) Iron (C) Wilkinson catalyst rightarrow$\rightarrow$ (I) Rhodium (D) Vitamin B_12$B_{12}$ rightarrow$\rightarrow$ (II) Cobalt This strictly maps to sequence A-IV, B-III, C-I, D-II. ### Pattern Recognition Always memorize the central metal for famous catalysts and biomolecules: Chlorophyll (Mg), Haemoglobin (Fe), Vitamin B12 (Co), Wilkinson (Rh), Ziegler-Natta (Ti). ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Chemistry: Coordination Compounds Class 12 Chemistry: d and f Block Elements

### Core Logic Let's examine the structure of each polynuclear metal carbonyl: 1. **[Co_2(CO)_8]$[Co_2(CO)_8]$**: Solid octacarbonyldicobalt(0) exists in a bridged structure. It has a Co-Co$Co-Co$ bond and two bridging CO$CO$ ligands, along with three terminal CO$CO$ ligands on each cobalt atom. So, it contains bridging CO groups. 2. **[Mn_2(CO)_10]$[Mn_2(CO)_{10}]$**: Decacarbonyldimanganese(0) has a single Mn-Mn$Mn-Mn$ bond and all 10 CO ligands are terminal. It does NOT have any bridging carbonyls. 3. **[Os_3(CO)_12]$[Os_3(CO)_{12}]$**: Dodecacarbonyltriosmium(0) forms a triangular cluster of Os atoms with all 12 CO ligands being terminal. 4. **[Ru_3(CO)_12]$[Ru_3(CO)_{12}]$**: Dodecacarbonyltriruthenium(0) similarly forms a triangular Ru_3$Ru_3$ cluster where all 12 CO ligands are terminal. ### Step 1: Conclusion Only [Co_2(CO)_8]$[Co_2(CO)_8]$ features CO$CO$ forming a bridge between the metal atoms. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Chemistry: Coordination Compounds

### Core Logic Decacarbonyldimanganese(0) is Mn_2(CO)_10$Mn_2(CO)_{10}$. In this binuclear carbonyl, there is one Mn-Mn$Mn-Mn$ bond. Each Mn$Mn$ atom is additionally bonded to five carbonyl (CO$CO$) ligands. Therefore, the coordination number of each Mn$Mn$ atom is 1 + 5 = 6$1 + 5 = 6$. The arrangement of these 6 bonds around each Mn$Mn$ atom is octahedral.

### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Chemistry: Coordination Compounds

### Core Logic Optical isomerism is shown by complexes that are chiral, meaning they lack both a plane of symmetry (POS) and a center of symmetry (COS). 1. cis-[mathrmCr(ox)_2mathrmCl_2]^3-$cis-[\mathrm{Cr}(ox)_2\mathrm{Cl}_2]^{3-}$: Cis configuration with bidentate ligands lacks a POS/COS. rightarrow$\rightarrow$ Shows optical isomerism. 2. [mathrmCo(en)_3]^3+$[\mathrm{Co}(en)_3]^{3+}$: Tris(bidentate) complex lacks POS/COS. rightarrow$\rightarrow$ Shows optical isomerism (exists as Delta$\Delta$ and Lambda$\Lambda$ enantiomers). 3. cis-[mathrmPt(en)_2mathrmCl_2]^2+$cis-[\mathrm{Pt}(en)_2\mathrm{Cl}_2]^{2+}$: Cis configuration lacks POS/COS. rightarrow$\rightarrow$ Shows optical isomerism. 4. cis-[mathrmCo(en)_2mathrmCl_2]^+$cis-[\mathrm{Co}(en)_2\mathrm{Cl}_2]^{+}$: Cis configuration lacks POS/COS. rightarrow$\rightarrow$ Shows optical isomerism. 5. trans-[mathrmPt(en)_2mathrmCl_2]^2+$trans-[\mathrm{Pt}(en)_2\mathrm{Cl}_2]^{2+}$: Trans configuration is highly symmetric and contains a POS (along the square plane). rightarrow$\rightarrow$ Cannot show optical isomerism. 6. trans-[mathrmCr(ox)_2mathrmCl_2]^3-$trans-[\mathrm{Cr}(ox)_2\mathrm{Cl}_2]^{3-}$: Trans configuration contains a POS/COS. rightarrow$\rightarrow$ Cannot show optical isomerism. ### Step 1: Final Tally Out of the 6 complexes, 4 can show optical isomerism. The answer is 4. ### Pattern Recognition For octahedral complexes with bidentate ligands: cis$cis$ isomers generally show optical isomerism, whereas trans$trans$ isomers have a plane of symmetry and are optically inactive. [M(L-L)_3]$[M(L-L)_3]$ types are always chiral. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Chemistry: Coordination Compounds

### Core Logic AlCl_3$AlCl_3$ dissolves in acidified water to form the hexaquaaluminium(III) complex ion. The reaction can be represented as: AlCl_3 + 6H_2O rightarrow [Al(H_2O)_6]^3+ + 3Cl^-$AlCl_3 + 6H_2O \rightarrow [Al(H_2O)_6]^{3+} + 3Cl^-$ ### Step 1: Analyzing Geometry The central aluminium atom coordinates with 6 water molecules, giving a coordination number of 6. A coordination number of 6 results in an octahedral geometry (sp^3d^2$sp^3d^2$ hybridization). ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Chemistry: Coordination Compounds Class 11 Chemistry: The p-Block Elements