How many stereoisomers does [Pt Br4 Cl2]2- have?
I think it has 2 geo., but how many optical?
To determine the number of stereoisomers for the complex [PtBr4Cl2]2-, we need to consider both geometrical (cis-trans) and optical (enantiomeric) isomerism.
First, let's consider the geometrical isomerism. For complexes with coordination number 6, such as [PtBr4Cl2]2-, the possible geometrical isomers are cis and trans. Cis isomers have similar ligands located on the same side of the central atom, whereas trans isomers have similar ligands located on opposite sides of the central atom.
In this case, since the complex has two different types of ligands (Br and Cl), the cis isomer can have the Br ligands on one side and the Cl ligands on the other side, or vice versa. Similarly, the trans isomer can have the Br and Cl ligands on opposite sides. Therefore, there are two possible geometrical isomers for [PtBr4Cl2]2-: cis and trans.
Moving on to optical isomerism, we need to determine if the complex has a chiral center. A chiral center is a central atom that is bonded to different ligands in a way that results in non-superimposable mirror images. In the case of [PtBr4Cl2]2-, the central Pt atom is bonded to four Br ligands and two Cl ligands. Since there are no two different ligands on the central Pt atom, the complex does not possess a chiral center. Therefore, there are no optical isomers for [PtBr4Cl2]2-.
In summary, the complex [PtBr4Cl2]2- has two geometrical isomers (cis and trans) but no optical isomers.