Chiral complex from the following is:
Here en = ethylene diamine

We need to identify the chiral complex. A complex is chiral if its mirror image is non-superimposable on the original.

Option A: cis-[PtCl₂(en)₂]²⁺

This is an octahedral complex. Ethylenediamine (en) is a bidentate ligand that chelates through two nitrogen atoms. With two en ligands and two Cl⁻ in cis positions, the complex has the form:

The two Cl⁻ are adjacent to each other, and the two en ligands span the remaining positions. This arrangement has no plane of symmetry and no improper rotation axis. The mirror image of this complex cannot be superimposed on the original.

This is analogous to the well-known chiral complex cis-[Co(en)₂Cl₂]⁺, which exists as Λ (lambda) and Δ (delta) enantiomers. This complex is chiral.

Option B: trans-[PtCl₂(en)₂]²⁺

In the trans arrangement, the two Cl⁻ are on opposite sides. This creates a plane of symmetry passing through the two Cl atoms and the metal center. Not chiral.

Option C: cis-[PtCl₂(NH₃)₂]

This is a square planar complex (Pt²⁺ with 4 monodentate ligands). All atoms lie in the same plane (the molecular plane), which is itself a plane of symmetry. Not chiral.

Option D: trans-[Co(NH₃)₄Cl₂]⁺

Octahedral with all monodentate ligands in trans arrangement. Multiple planes of symmetry exist. Not chiral.

The answer is Option A: cis-[PtCl₂(en)₂]²⁺.