The number of isomers possible for [Pt(en)(NO2)2] is:

🧠 Pt(en)(NO₂)₂ — Geometry First

$[\mathrm{Pt(en)(NO_2)_2}]$: Pt(II) is d⁸ → square planar. Ligands: 1 en (bidentate, occupies adjacent positions) + 2 NO₂ (ambidentate).

In square planar with bidentate en, the two NO₂ are forced cis to each other (the only available positions).

🗺️ Linkage Isomerism of NO₂

NO₂⁻ is ambidentate: bonds via N (nitro, $\mathrm{-NO_2}$) or O (nitrito, $\mathrm{-ONO}$).

For 2 NO₂ ligands, the linkage combinations are:

1. Both N-bonded: $-\mathrm{NO_2}, -\mathrm{NO_2}$
2. Both O-bonded: $-\mathrm{ONO}, -\mathrm{ONO}$
3. Mixed: $-\mathrm{NO_2}, -\mathrm{ONO}$ (only one mixed combination — the two NO₂ positions are equivalent by the en C₂ axis)

→ 3 isomers.

🗺️ Geometric Isomerism Check

In sq pl with en: the two NO₂ must be cis. No trans option. So no geometric isomers. Only linkage isomers.

⚡ Counting Linkage Isomers

For $n$ ambidentate ligands, naive count = $2^n$, but symmetry-equivalent positions reduce this. With en's $C_2$ axis swapping the two NO₂ positions, NN ≡ NN, OO ≡ OO, NO ≡ ON → 3 distinct.

⚠️ Pt(II) Always Square Planar

Pt(II) d⁸ is rigorously sq pl regardless of ligand strength — strong CFSE preference. No tetrahedral Pt(II).

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