What is coordination number of central metal ion in cisplatin ?

Cisplatin is cis-diamminedichloridoplatinum(II), with the chemical formula $[Pt(NH_3)_2Cl_2]$.

The central metal ion is $Pt^{2+}$, which is coordinated to two ammonia (NH_3$) ligands and two chloride (Cl^-$) ligands.

Since both $NH_3$ and $Cl^-$ are monodentate ligands, the total number of coordinate bonds formed with the central metal ion is $2 + 2 = 4$.

Thus, the coordination number of the central metal ion in cisplatin is $4$.

Answer: $4$