The IUPAC name of the complex \([Pt(NH_3)_2Cl(NH_2CH_3)]Cl\) is:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Diamminechlorido(methanamine)platinum(II) chloride
A coordination compound is named by the IUPAC rules: the cation is named first; inside the complex the ligands come in alphabetical order before the metal; the metal’s oxidation state follows in Roman numerals.
Ligands: 2 \( \ce{NH3} \) = diammine (double “m”), \( \ce{Cl-} \) = chlorido, \( \ce{CH3NH2} \) = (methanamine), written in brackets because it is an organic ligand. Alphabetical order: ammine, chlorido, methanamine.
Oxidation state of Pt: one \( \ce{Cl-} \) outside the bracket makes the complex ion +1. So x + 2(0) + (−1) + 0 = +1, which gives x = +2.
Option (1) Diaminechloromethylamineplatinum(II) chloride — Incorrect. “Diamine” (single m) means a ligand with two amino groups, not two \( \ce{NH3} \) molecules. The anionic ligand must be named chlorido, not chloro, and the organic ligand needs brackets.
Option (2) Diaminechloridomethylamineplatinum (III) chloride — Incorrect. It uses “diamine” and gives platinum the oxidation state +3; the charge balance gives +2.
Option (3) Diamminechlorido(methylamine)platinum(IV) chloride — Incorrect. The ligands are named acceptably, but platinum is given the oxidation state +4. With one chloride outside the sphere the complex ion is \( \ce{[Pt(NH3)2Cl(NH2CH3)]^+} \), so Pt is +2.
NCERT (2026-27 edition):
Naming of Mononuclear Coordination Compounds – “… (i) The cation is named first in both positively and negatively charged coordination entities.
(ii) The ligands are named in an alphabetical order before the name of the central atom/ion. (This procedure is reversed from writing formula).
(iii) Names of the anionic ligands end in –o, those of neutral and cationic ligands are the same except aqua for H2O, ammine for NH3, carbonyl for CO and nitrosyl for NO. While writing the formula of coordination entity, these are enclosed in brackets ( ). …
(v) Oxidation state of the metal in cation, anion or neutral coordination entity is indicated by Roman numeral in parenthesis.”