Chiral Metal Complexes
Numbers in square brackets refer to the List of Publications
Chiral Phosphines & Chiral Complexes
This is a field we have entered only recently. Out of our work on the use of transition metal complexes as chiral auxiliaries (see Sulfur Chemistry) a need for chiral chelate phosphines with special properties arose. As a first example, (2S,3S)-bis(dibenzophospholyl)butane, a rigid analog of the well-known (S,S)-CHIRAPHOS was synthesized and converted into a series of ruthenium complexes .
Following up on our earlier work on chiral (still racemic) rhenium thiolate and thioaldehyde complexes of the types [CpRe(NO)(PR3)(SCH2R')] and [CpRe(NO)(PR3)(S=CHR')]+ [70, 91, 93, 96] we began to investigate new methods to obtain such complexes in enantiomerically pure form. Quite promising in this regard were chiral, hemilabile (P,O)- and (P,S) ligands which could easily be converted into diastereomeric rhenium complexes. These complexes were found to undergo reversible chelate ring closure / ring opening reactions [118, 119].
Similar (P,N) ligands proved to be even more useful as they provided a direct access to enantiomerically pure half-sandwich rhenium complexes through a diastereoselective proton transfer step .
These complexes will now be investigated as templates in diastereoselective addition reactions of coordinated ligands.