Chapter 2, Problem 26P

Interpretation Introduction

Interpretation:

1. The possible stereoisomers for the trigonal bipyramidal ${\left[{\text{SiF}}_{\text{3}}{\text{Me}}_{\text{2}}\right]}^{\text{-}}$ anion (Me = ${\text{CH}}_3$) is to be drawn. An X-ray diffraction study of a salt of ${\left[{\text{SiF}}_{\text{3}}{\text{Me}}_{\text{2}}\right]}^{\text{-}}$ shows that two F atoms occupy axial sites, this isomer is preferred over the other possible structures is to be explained.

2. The members of the series of complexes ${\left[{\text{PtCl}}_{\text{4}}\right]}^{\text{2-}}$, ${\left[{\text{PtCl}}_{\text{3}}{\text{(PMe}}_3\text{)}\right]}^{\text{-}}$, $\left[{\text{PtCl}}_2{{\text{(PMe}}_3\text{)}}_2\right]$ and ${\left[{\text{PtCl(PMe}}_3{\text{)}}_3\right]}^{+}$ do not possess the same number of stereoisomers is to be explained.

Concept Introduction:

If two species have the same molecular formula and same atom connectivity, but the atoms arepositioned differently in spaceabout a central atom or a double bond, then the compounds are stereoisomers.

Stereoisomers are divided into two categories:

1. Enantiomers: They are chiral molecules that are mirror images of each other.

2. Diastereomers: They are molecules that are not mirror images of each other.

The VSEPR theory provides the simple model for predicting the shapes of molecular species based on minimizing the electrostatic repulsion of a molecule's valence electrons around a central atom.