The homoleptic complex from the following complexes is:

Solution & Explanation

\textbf{Answer:} (A) Potassium trioxalatoaluminate(III). \textbf{Solution:} A homoleptic complex contains only one kind of ligand bound to the metal; a heteroleptic complex contains more than one kind. Parsing each name into its coordination sphere: Potassium trioxalatoaluminate(III) = $\mathrm{K}{}_3[\mathrm{Al}(\mathrm{C}{}_2\mathrm{O}{}_4){}_3]$ — only oxalate ligands → homoleptic. Diamminechloridonitrito-N-platinum(II) = $[\mathrm{Pt}(\mathrm{NH}{}_3){}_2\mathrm{Cl}(\mathrm{NO}{}_2)]$ — ammine, chlorido and nitrito ligands → heteroleptic. Pentaamminecarbonatocobalt(III) chloride = $[\mathrm{Co}(\mathrm{NH}{}_3){}_5(\mathrm{CO}{}_3)]\mathrm{Cl}$ — ammine and carbonato → heteroleptic. Triamminetriaquachromium(III) chloride = $[\mathrm{Cr}(\mathrm{NH}{}_3){}_3(\mathrm{H}{}_2\mathrm{O}){}_3]\mathrm{Cl}{}_3$ — ammine and aqua → heteroleptic. Only $\mathrm{K}{}_3[\mathrm{Al}(\mathrm{C}{}_2\mathrm{O}{}_4){}_3]$ has a single type of ligand, so the homoleptic complex is option (A).