To Coordinate or not to Coordinate: The Special Role of Chalcogen Ether Functionalities in the Design of Twofold Functionalized Cyclopentadienyl Ligands [Cp,O,Ch (Ch = S, Se)]

The solvent- and catalyst free synthesis of two β-thio ketones L1a and L1b is reported. L1a, L1b, and a β-seleno ketone L1c were successfully employed as ligand precursors in the synthesis of a novel series of cationic titanium complexes 4a–4c via a well-established reaction sequence: insertion of the carbonyl functional group into the polarized Ti–C q,exo bond of the monopentafulvene complex Cp*Ti(Cl)(π-η 5 :σ–η 1 -C 5 H 4 =CR 2 ) (1) (CR 2 = adamantylidene), subsequent methylation, and final activation with B(C 6 F 5 ) 3 . The cationic titanium complexes 4a–4c bear twofold functionalized cyclopentadienyl [Cp,O,Ch (Ch = S, Se)] ligand frameworks built directly in the coordination sphere of the metal, in which the chalcogen ether functionalities do not coordinate to the central metal atoms as demonstrated by NMR experiments. Consequently, Cp,O σ,π chelating ligand systems are formed with free coordination sites at the central titanium atoms and pendant chalcogen ether moieties.