FLP behaviour of cationic titanium complexes with tridentate Cp,O,N-ligands: highly efficient syntheses and activation reactions of C–X bonds (X = Cl, F)

Abstract

The synthesis of cationic titanium complexes 4a,b with tridentate Cp,O,N-ligand frameworks, starting from the monopentafulvene complex Cp*Ti(Cl)(π-η⁵:σ-η¹-C₅H₄CR₂ (CR₂ = adamantylidene) (1) and bidentate O,N-ligand precursors CH₃C(O)CH₂CH₂NR₂ (R = Et, CH₂Ph) (L1a,b), in a high-yielding and efficient two-step synthetic pathway is described. The β-aminoketones L1a,b were synthesized by a herein reported solvent- and catalyst-free reaction. The reaction pathway involves insertion reactions, subsequent methylations and final activations with B(C₆F₅)₃. NMR investigations of the cationic titanium complex 4a in deuterated dichloromethane revealed an ongoing selective reaction under formation of the cationic complex 5a-d₂, which is the result of C–Cl bond cleavage. In addition to selective C–Cl bond activation reactions, C(sp³)–F bonds were activated by 4a,b, pointing out the special tm-FLP nature of 4a,b.