Class XII Coordination Chemistry - Unit Test II

Vocabulary flashcards covering fundamental terms and core concepts from Class XII Unit 5: Coordination Chemistry.

Limitations of Valence Bond Theory (VBT)

Key weaknesses of VBT in coordination chemistry, including its inability to explain the color and electronic absorption spectra of complexes, lack of quantitative interpretation of magnetic data, and failure to differentiate between weak-field and strong-field ligands.

Crystal Field Stabilization Energy (CFSE)

The net decrease in electronic energy that results from the splitting of degenerate d-orbitals when a central metal ion is placed in a ligand field, relative to the energy of an isotropic spherical field.

Crystal Field Splitting

The lifting of degeneracy and separation of the five degenerate d-orbitals of a central transition metal ion into different energy sublevels as a result of electrostatic repulsion by surrounding ligands.

Color Difference: $[Ti(H_2O)_6]^{3+}$ vs $[Sc(H_2O)_6]^{3+}$

$[Ti(H_2O)_6]^{3+}$ is coloured because $Ti^{3+}$ possesses a $d^1$ configuration, allowing a $d\text{-}d$ electron transition upon absorbing visible light, whereas $[Sc(H_2O)_6]^{3+}$ is colourless because $Sc^{3+}$ has an empty $d^0$ configuration and cannot undergo $d\text{-}d$ transitions.

Octahedral Crystal Field Splitting

The pattern where the five degenerate d-orbitals split into a lower-energy triply degenerate set ($t_{2g}$: $d_{xy}$, $d_{yz}$, $d_{zx}$) and a higher-energy doubly degenerate set ($e_g$: $d_{x^2-y^2}$, $d_{z^2}$), separated by the energy difference $\Delta_o$.

Tetrahedral Crystal Field Splitting

The pattern where the five degenerate d-orbitals split into a lower-energy doubly degenerate set ($e$: $d_{x^2-y^2}$, $d_{z^2}$) and a higher-energy triply degenerate set ($t_2$: $d_{xy}$, $d_{yz}$, $d_{zx}$), separated by the energy difference $\Delta_t$.

Absence of Geometrical Isomerism in Tetrahedral Complexes

Tetrahedral complexes cannot exhibit cis-trans (geometrical) isomerism because all four ligand positions are adjacent and geometrically equivalent to one another, maintaining identical bond angles of approximately $109.5^\circ$.

Coordination Compounds in Medicine

Complexes used for therapeutic applications, notably Cisplatin ($[Pt(NH_3)_2Cl_2]$) as an antineoplastic agent in cancer chemotherapy, and Ca-EDTA used in chelation therapy for treating lead poisoning.

Biological Importance of Coordination Compounds

Vital biomolecules containing coordinated metal ions, such as Chlorophyll (a magnesium-porphyrin complex driving photosynthesis) and Hemoglobin (an iron-porphyrin complex responsible for oxygen transport in blood).

Stability Constant

The equilibrium constant ($K$ or $\beta$) for the formation of a coordination complex from its central metal ion and ligands in solution, quantifying the thermodynamic stability of the complex.

Wilkinson Catalyst

The coordination complex chloridotris(triphenylphosphine)rhodium(I), with the chemical formula $[(C_6H_5)_3P]_3RhCl$, widely used as a homogeneous catalyst for the selective hydrogenation of alkenes.

Ziegler–Natta Catalyst

A catalyst system comprising titanium tetrachloride ($TiCl_4$) and triethylaluminium ($Al(C_2H_5)_3$), utilized industrially for the coordination polymerization of ethene and other alkenes to yield stereoregular, high-density polymers.

Bonding in Metal Carbonyls

A synergic bonding mechanism consisting of a $\sigma$-bond formed by donation of the carbonyl carbon lone pair into a vacant metal d-orbital, reinforced by a $\pi$-back bond formed by metal d-electron donation into empty antibonding $\pi^*$ orbitals of $CO$.