Formation of Specific Configurations at Stereogenic Nitrogen Centers upon Their Coordination to Zinc and Mercury

Abstract

The coordination of (R,R)-tetramethylcyclohexane-1,2-diamine derivatives with stereogenic nitrogen centers to zinc and mercury halides is investigated. It is shown that the resulting complexes display one specific configuration at the stereogenic nitrogen centers. This fact is unusual due to the fast inversion of nitrogen centers but highly desirable as the stereoinformation of the ligands is brought closer to the metal centers of the potential catalysts. A combination of NMR studies and quantum chemical calculations gives insight into the selective formation of one specific configuration at the stereogenic nitrogen centers of the zinc complexes.

Structural studies of diaminocyclohexane-containing aza-crown ether macrocycles and their Zn(II) complexes

“…The overall correspondence of signals between the spectra of the free ligand and complex in the slow exchange regime indicates that the C 2 symmetry of the system is preserved upon metal binding (i.e. both stereogenic N atoms adopt the same configuration in the complex), which is commonly observed in the complexes of DACH derivatives with tetrahedral metal ions [40][41][42][43]. Crystals of the complex (R)-2:ZnCl 2 were obtained by slow evaporation from d 4 -methanol and characterized by X-ray crystallography.…”

Exploring the Synthesis of a New Group of Chiral Ammonium Salts with Specific Configurations at the Stereogenic Nitrogen Centers

“…In this context we decided to explore the stereoselective synthesis of a new group of chiral ammonium salts containing stereogenic nitrogen centers with fixed, specific configurations. We aimed at providing a model dication that was not based on cinchona alkaloids but on a derivative of chiral (1 R ,2 R )‐tetramethylcyclohexane‐1,2‐diamine: N ‐propyl‐ N , N ′, N ′‐trimethyl‐(1 R ,2 R )‐cyclohexane‐1,2‐diamine ( 3 ) 6. This diamine has a great advantage over cinchona alkaloids: its ( S , S )‐configured enantiomer is also readily available.…”

“…If, however, not a mixture of both configurations but one specific configuration were fixed at the stereogenic nitrogen center, an ideal model cation would be generated. This could then be easily adapted for applications such as chiral micelles by employing derivatives with sterically more demanding substituents instead of the propyl group at the nitrogen center6, 8 and by using diamines with two identical stereogenic nitrogen centers.…”

Synthesis of Organosilicon‐Based Thioether Ligand Class Showing Defined S‐Stereogenic Coordination in Crystalline Palladium(II) Complexes

“…[14] A similar process can be observed for nitrogen inversion after the nitrogen atom becomes a stereogenic centre by coordinating to a transition metal, which was previously investigated in our group. [21][22][23][24][25][26] Also, we analysed the inversion of sulphur stereogenic centres in cis-platinum(II) complexes by temperature dependent 195 Pt-NMR. [4] Other studies on similar topics are known as well.…”