Question

what are the symmetry elements for:

cis-CoCl2(NH3)4
and
trans-CoCl2(NH3)4

would it be C2 S2?

Answer 1

For cis-CoCl2(NH3)4:

The symmetry elements present are:

1. C3 (3-fold rotation axis): This is a rotation axis that goes through the cobalt atom and bisects the complex into three equal parts.
2. Three σv planes (vertical mirror planes): These mirror planes pass through the central cobalt atom and the two cis-chloro ligands.

For trans-CoCl2(NH3)4:

The symmetry elements present are:

1. C2 (2-fold rotation axis): This is a rotation axis that goes through the cobalt atom and bisects the complex into two equal parts.
2. Two σv planes (vertical mirror planes): These mirror planes pass through the central cobalt atom and the two trans-chloro ligands.
3. σh plane (horizontal mirror plane): This mirror plane corresponds to the plane formed by the cobalt atom and the two trans-chloro ligands.

As noted, the cis-isomer has C3 and three σv planes (not C2 and S2), while the trans-isomer has C2, two σv planes, and one σh plane.