The compound that inhibits the growth of tumors is:

🧠 The cis-Platin Anchor

The drug that inhibits tumour growth is cis-platin, the cis isomer of $[\mathrm{Pt(NH_3)_2Cl_2}]$.

Two structural facts make it active:

1. cis geometry — the two Cl ligands are 90° apart, allowing both to leave and bind to adjacent N atoms on DNA.
2. Pt(II) centre — kinetically slow, so the complex survives in the bloodstream long enough to reach tumour cells.

The trans isomer is biologically inactive (the two Cls are 180° apart and cannot bind adjacent DNA bases). Pd analogues are too labile (Pd-Cl exchange is fast) → no useful pharmacology.

🗺️ Eliminate Each Wrong Option

• (1) trans-$[\mathrm{Pt(Cl)_2(NH_3)_2}]$ — wrong geometry; cannot crosslink DNA. ✗
• (2) cis-$[\mathrm{Pt(Cl)_2(NH_3)_2}]$ — cis-platin, the antitumour drug. ✓
• (3) cis-$[\mathrm{Pd(Cl)_2(NH_3)_2}]$ — too labile, hydrolyses before reaching the tumour. ✗
• (4) trans-$[\mathrm{Pd(Cl)_2(NH_3)_2}]$ — wrong on both counts. ✗

⚡ The "Pt + cis = Drug" Mnemonic

Three flags must align: Pt (slow kinetics), cis (geometry for DNA crosslinking), square-planar Pt(II) (correct geometry). Miss any one → not antitumour.

⚠️ Don't Confuse Pt and Pd

Both are group-10 d⁸ metals with similar electron count, but Pd–L bond exchange is ~10⁵ times faster than Pt–L. Pd can't survive in bloodstream long enough to act as a drug.

$\boxed{\text{Answer: (2) cis-}[\mathrm{Pt(Cl)_2(NH_3)_2}]}$