Question

Fac and Mer isomerism is associated with which of the following general formula?

• A. $\left[M\right(AA{)}_2]$
• B. $\left[MABCD\right]$
• C. $\left[M\right(AA{)}_3]$
• D. $\left[M{A}_3{B}_3\right]$

Answer 1

Answer: (D)

The compounds of the formula $\left[M{A}_3{B}_3\right]$ exhibit fac and mer isomerism.
The fac isomer is also known as facial isomer or cis isomer. Three A ligands are present on one triangular face and three B ligands are present on opposite triangular face.
The mer isomer is also known as meridional isomer or trans isomer.