Geo-Scientist Prelims 2025 Chemistry Q28: Consider the following structures :

Consider the following structures :

1. [Co] with Cl, Cl, NH₃, NH₃, NH₃, NH₃; the two Cl on adjacent vertices (structure 1)
2. [Co] with Cl, Cl, NH₃, NH₃, NH₃, NH₃; the two Cl on opposite vertices (structure 2)
3. [Ru] with Cl, Cl, Cl, H₂O, H₂O, H₂O; the three Cl on one face, each opposite an H₂O (structure 3)
4. [Ru] with Cl, Cl, Cl, H₂O, H₂O, H₂O; two Cl opposite each other, all three Cl in one plane (structure 4)

Which one of the following statements is correct for the structures given above ?

1. (a) 1 and 2 are cis and trans tetraamminedichlorocobalt(III) and 3 and 4 are cis and trans triaquatrichlororuthenium(III) isomeric pairs.
2. (b) 1 and 2 are cis and trans tetraamminedichlorocobalt(III) and 3 and 4 are fac and mer triaquatrichlororuthenium(III) isomeric pairs.
3. (c) 1 and 2 are fac and mer tetraamminedichlorocobalt(III) and 3 and 4 are cis and trans triaquatrichlororuthenium(III) isomeric pairs.
4. (d) 1 and 2 are fac and mer tetraamminedichlorocobalt(III) and 3 and 4 are fac and mer triaquatrichlororuthenium(III) isomeric pairs.