Construction of chiral Ti(IV)–Rh(I)–salenophos complexes and their application in the asymmetric hydroformylation of functionalised olefins

The synthesis of new chiral salenophos-type ligands bearing `hard' and `soft' coordination sites is described. The polyfunctionalised ligands are used for the construction of monometallic and early–late heterobimetallic complexes. In the reaction with titanium(IV) reagents the salen subunit selectively coordinated to the `hard' metal. The phosphine groups in turn can be coordinated to rhodium(I). The coordination geometry of the diphosphine–Rh subunit is strongly influenced by the counter ligands COD or CO and Cl, respectively. In the asymmetric hydroformylation of vinyl acetate with one of the Rh–Ti-complexes, the branched aldehyde is predominantly formed with 30% ee.