Optical Isomerism in Tetrahedral Complexes

The preparation, and even more the resolution, of an asymmetric tetrahedral center in Werner-type complexes has been thwarted by the configurational instability of tetrahedral complexes. However the use of ligands of the strongly a, 7t bonding type imposes stability and the forma- 

The stereoisomerism in some asymmetric tetrahedral complexes of the type M(AA,)2 has been characterized by nmr. - Tetrahedral complexes of the type M(AA,)2 are chiral, but their lability requires nmr methods for measurement of the rates of interconversion of the enantiomers. The pioneering work of Holm and his collaborators has been consolidated by Minkin and his Russian group and Zn, Cd and, more recently, Ni chelates of the type M(AA[)2 have been extensively studied. 

The rigid chelate 8 destabilizes the planar form and reduces the lability of the tetrahedral planar rearrangement (Sec. 7.2.1). 

---