What is the IUPAC name of [Pt(NH_3)_2Cl_2] ?

The correct answer is Option (2) → Diamminedichloridoplatinum (II)

The IUPAC name of a neutral complex is written in this order: the ligands in alphabetical order (prefixes such as di- and tri- are ignored when alphabetising), then the name of the metal, then its oxidation state in Roman numerals in brackets. Neutral \( \ce{NH3} \) is named ammine and the anion \( \ce{Cl^{-}} \) is named chlorido.

The oxidation state of platinum follows from the charge balance (the complex is neutral, \( \ce{NH3} \) is neutral, each chloride is −1):

    \( \displaystyle x + 2(0) + 2(-1) = 0 \Rightarrow x = +2 \)

“ammine” (a) comes before “chlorido” (c), so the name is diamminedichloridoplatinum(II). Its cis isomer is the anticancer drug cisplatin.

Why the other options are incorrect

• Option (1) Diamminedichloridoplatinum (IV) — Incorrect. Platinum would be +4 only if the ligands carried a total charge of −4, for example in \( \ce{[Pt(NH3)2Cl4]} \).

• Option (3) Diamminedichloridoplatinum (0) — Incorrect. A zero oxidation state needs only neutral ligands; the two chloride ions make platinum +2.

• Option (4) Dichloridodiammineplatinum (IV) — Incorrect. Wrong on both counts: the ligands are not in alphabetical order (ammine must come before chlorido), and the oxidation state of platinum is +2, not +4.

NCERT (2026-27 edition):
Naming of Mononuclear Coordination Compounds – “… (ii) The ligands are named in an alphabetical order before the name of the central atom/ion. (This procedure is reversed from writing formula).
… (v) Oxidation state of the metal in cation, anion or neutral coordination entity is indicated by Roman numeral in parenthesis.”

Note: The same/similar question has been asked in different years by NTA as per the details given below: