Question

A four-coordinate complex \(\mathrm{MA}_{2} \mathrm{~B}_{2}\) is prepared and found to have two different isomers. Is it possible to determine from this information whether the complex is square planar or tetrahedral? If so, which is it?

Short answer

Based on the given information that the four-coordinate complex MA2B2 has two different isomers, it is possible to determine that the complex is square planar. This is because a square planar arrangement can have two possible isomers (cis and trans), whereas a tetrahedral arrangement can only have one isomer. Thus, the complex is square planar.

Step-by-step solution

Understand the given information

We know that the complex is composed of four ligands, with two of each type (A and B). Two different isomers are found, which implies that there are two different ways to arrange these ligands around the metal.

Consider square planar arrangement

In a square planar arrangement, the ligands are at the corners of a square, with the metal ion at the center. In this case, there are two possible isomers: cis and trans. These two isomers occur when the same type of ligands (either A or B) are either adjacent to each other (cis) or directly opposite each other (trans).

Consider tetrahedral arrangement

In a tetrahedral arrangement, the ligands are placed at the corners of a tetrahedron, with the metal ion at the center. In this case, there is only one possible isomer, as all the corners are equivalent. Any arrangement of the ligands A and B will be the same isomer.

Identify the type of complex

Since we are given that the four-coordinate complex MA2B2 has two different isomers, this implies that the complex must be square planar (with cis and trans isomers). A tetrahedral arrangement would only have one isomer. Therefore, the complex is square planar.