Related Experiment Video
Updated: Jul 3, 2026

Development of Heterogeneous Enantioselective Catalysts using Chiral Metal-Organic Frameworks (MOFs)
Published on: January 17, 2020
Enantiomerically pure titanium complexes containing an [OSSO]-type bis(phenolate) ligand: synthesis, structure, and
Geert-Jan M Meppelder1, Klaus Beckerle, Ramanujachary Manivannan
1Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52056 Aachen, Germany.
Abstract:
Chiral 1,2-trans-dithiocyclohexanediyl-bridged bis(phenols) of the type [2,2'-{HOC(6)H(2)-6-R(1)-4-R(2)}(2)S(2)C(6)H(10)] ([OSSO]H(2), R(1)=tBu, iPr, H; R(2)=tBu, iPr, Me) could be conveniently and selectively synthesized in three steps, starting from cyclohexene oxide and arene thiolate. The racemic bis(phenols) could be resolved using an enantiopure (S)-camphorsulfonic ester auxiliary or by (chiral) HPLC. Complexation of the racemic bis(phenols) to TiX(4) (X=Cl, OiPr) proceeds in a diastereoselective fashion to give only the Lambda,R,R and Delta,S,S enantiomers. Racemic [Ti{(OC(6)H(2)-6-tBu-4-Me)(2)S(2)C(6)H(10)}Cl(2)] reacts with benzyl magnesium bromide to afford the crystallographically characterized dibenzyl complex. The benzyl cation formed using B(C(6)F(5))(3) in C(6)D(5)Br slowly decomposes at temperatures above +10 degrees C. When treated with methylaluminoxane, the dichloro complexes [Ti{OSSO}Cl(2)] polymerize styrene with activities up to 146 kg (mol catalyst)(-1) [styrene (mol L(-1))](-1) h(-1); diisopropoxy complexes [Ti{OSSO}(OiPr)(2)] show mere trace activity. With 1-hexene as a chain-transfer agent, activated enantiopure titanium complexes give low-molecular-weight homochiral isotactic oligostyrenes, terminated by one to five 1-hexene units with M(n) values as low as 750 g mol(-1) for R=tBu and 1290 g mol(-1) for R=Me. Below M(n) approximately 5000 these oligostyrenes show optical activity.
Related Concept Videos
Sharpless Epoxidation
Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
Stereoisomerism
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction

