Metal complexes derived from a bidentate ligand possessing two chiral centres, o-C6H4[CH(SiMe3)–]2; stereospecific synthesis of the meso-metallocycles [M{CH(SiMe3)C6H4CH(SiMe3)-o}(η-C5H5)2] and their reversible one-electron reduction

Reaction of [M(η-C5H5)2Cl2](M = Ti, Zr, or Hf) with o-C6H4[CH(SiMe3)Li(tmeda)]2(tmeda = Me2NCH2CH2NMe2) in OEt2 is stereospecific, generating the meso-metallocycle [[graphic omitted]H(SiMe3)-o}(η-C5H5)2], (1), in high yield; cyclic voltammetry of complexes (1) in tetrahydrofuran shows a reversible one-electron reduction (â E ½ ^red: Hf > Zr >> Ti) to yield relatively persistent M^III anions (t ½ > 10 s) characterised by their e.s.r. spectra.