89 questions on this topic of Coordination Compounds (NEET 2027 syllabus). Here are 12; tap one to see its answer and explanation.
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Answer: (D) [Co(NH₃)₃(NO₂)₃]
Facial-meridional (fac-mer) isomerism is a specific type of geometrical isomerism observed in octahedral complexes of the general formula [Ma₃b₃]. Among the given options, [Co(NH₃)₃(NO₂)₃] matches the [Ma₃b₃] formulation and exists as fac- and mer-isomers.
Answer: (C) Statement I is incorrect but Statement II is correct
Square planar complexes have a molecular plane of symmetry and therefore are achiral and do not exhibit optical isomerism, making Statement I incorrect. Tetrahedral complexes with four different ligands lack an alternating axis of symmetry (Sn), making them chiral and optically active, so Statement II is correct.
Answer: (A) Tetraamminedichloridoplatinum(IV) tetrachloridoplatinate(II)
The cation is named first, followed by the anion. For stable oxidation states of Pt (+2 and +4), the cation [Pt(NH₃)₄Cl₂]²⁺ contains Pt(IV) and the anion [PtCl₄]²⁻ contains Pt(II). Thus, the correct name is tetraamminedichloridoplatinum(IV) tetrachloridoplatinate(II).
Answer: (D) cis-[Cr(ox)₂(H₂O)₂]⁻
The complex cis-[Cr(ox)₂(H₂O)₂]⁻ lacks a plane or center of symmetry, making it chiral and optically active. In contrast, trans-[Cr(ox)₂(H₂O)₂]⁻ and trans-[Co(NH₃)₄Cl₂]⁺ possess a plane of symmetry, and square planar cis-[Pt(NH₃)₂Cl₂] lies entirely in a plane.
Answer: (D) [Pt(NH₃)₃Br]NO₂ and [Pt(NH₃)₃(NO₂)]Br
Ionization isomerism occurs when a counter ion displaces a ligand from the coordination sphere, giving different ions in aqueous solution. Here, Br⁻ and NO₂⁻ exchange positions between inside and outside the coordination sphere.
Answer: (B) 15
For an octahedral complex with six different unidentate ligands [Mabcdef], fixing one ligand gives 5 choices for the trans position. The remaining four equatorial positions yield 3 unique planar arrangements per choice, resulting in 5 × 3 = 15 geometrical isomers (each of which is chiral, forming 15 enantiomeric pairs, i.e., 30 stereoisomers in total).
Answer: (D) Potassium tetrahydroxidoaurate(III)
The complex anion has a -1 charge, [Au(OH)₄]⁻. Four hydroxido ligands give -4, making the oxidation state of Au equal to +3. Since the complex is anionic, the metal name ends in -ate with its Latin root (aurate). Thus, the correct name is potassium tetrahydroxidoaurate(III).
Answer: (A) 3
[Co(en)₂(Cl)₂]⁺ exists as two geometrical isomers: cis and trans. The trans isomer has a plane of symmetry and is optically inactive, while the cis isomer is chiral and exists as a pair of non-superimposable enantiomers (d and l forms). Therefore, there are 1 trans + 2 cis enantiomers = 3 stereoisomers in total.
Answer: (A) trans-[Co(en)₂(CN)₂]⁺
The trans isomer of [Co(en)₂(CN)₂]⁺ possesses a plane of symmetry (and a center of inversion), rendering it achiral and optically inactive. In contrast, tris-chelate complexes like [Co(en)₃]³⁺ and [Cr(ox)₃]³⁻, as well as cis-[Co(en)₂(CN)₂]⁺, lack improper rotation axes and are chiral.
Answer: (D) trans-[Co(en)₂Cl₂]⁺
trans-[Co(en)₂Cl₂]⁺ possesses a center of inversion as well as planes of symmetry perpendicular and parallel to the principal axis, rendering it achiral and optically inactive. In contrast, cis-[Pt(en)₂Cl₂]²⁺, [Co(en)₃]³⁺, and cis-[Cr(ox)₂(H₂O)₂]⁻ lack Sn axes (have no plane or centre of symmetry) and are chiral (optically active).
Answer: (C) [Co(NH₃)₄Cl₂]NO₂
[Co(NH₃)₄Cl₂]NO₂ has the formulation [Ma₄b₂]X, which exhibits cis-trans geometrical isomerism. Additionally, the exchange of an inner-sphere Cl⁻ with the outer-sphere NO₂⁻ yields [Co(NH₃)₄Cl(NO₂)]Cl, showing ionization isomerism.
Answer: (B) Bis(dimethylglyoximato)nickel(II)
Dimethylglyoximato is an anionic bidentate ligand carrying a -1 charge, so the prefix 'bis' is used. The complex is neutral with nickel in the +2 oxidation state (x + 2(-1) = 0, x = +2), giving bis(dimethylglyoximato)nickel(II).