Tetrahedral structures optical isomerism

The structure of thalidomide contains a tetrahedral carbon atom (coloured red) attached to four different groups. This implies that thalidomide exhibits optical isomerism. 

Cobalt(II) forms more tetrahedral complexes than any other ion except zinc(II). Draw the structure(s) of the tetrahedral complex [CoCl2(en)]. Could this complex exhibit geometric or optical isomerism If one of the CD ligands is replaced by Br, what kinds of isomerism, if any, are possible in the resulting compound ... 

Except for the simplest a-amino acid, glycine, NH2CH2COOH, the a-amino acids exist as enantiomers, or optical isomers. Such isomers are mirror images. Any molecule having one tetrahedral carbon atom bonded to four different groups of atoms exhibits optical isomerism. The mirror-image isomers are referred to as the D-isomer and the L-isomer their three-dimensional structures are represented by the following formulas ... 

The most common coordination number is six and such complexes have an octahedral structure. The next most common four-coordinated systems have either tetrahedral or square planar structures. Other complexes are known having different coordination numbers and structures. The stereochemistry of metal complexes is a fascinating subject. Several different types of isomeric structures are possible and have been demonstrated in these systems. For our purpose here it is sufficient to cite examples of geometrical (ds-trans) and optical isomerism. This can readily be iUustrated by the cis (III) and trans (IV) isomers of QCo(en)2Cl2]+. Note that the... 

The methane molecule is a very important molecule in organic chemistry, the geometry around the tetravalent carbon atom being basic to the understanding of the structure, isomerism and optical activity of a very large number of compounds. It is a tetrahedral molecule belonging to the tetrahedral point group, Td. 

In 1936, Mills and Clark published their findings on new thio-salts of Hg, Cd and Zn. They proposed a tetrahedral conformation and discovered a specific and reversible isomerization between two crystal forms. They noted that optical activity could possibly exist in these complexes and suggested it as the most probable explanation for the existence of the two modifications. The next, larger step in main group dithiolate chemistry came only in 1960, when Gilbert and Sandell prepared Mo(tdt)3 as the first neutral tris-dithiolate. While main groups dithiolates are still of broad interest, most of the recent work in this area has focused on structural questions. 

---