Four-Membered Heterometallacyclic d0 and d1 Complexes of Group 4 Metallocenes with Amidato Ligands

A study of the coordination chemistry of different amidato ligands [(R)N-C(Ph)O] (R = Ph, 2,6-diisopropylphenyl (Dipp)) at Group 4 metallocenes is presented. The heterometallacyclic complexes [Cp2M(Cl){kappa(2)-N,O-(R)N-C(Ph)O}] M = Zr, R = Dipp (1a), Ph (1b); M = Hf, R = Ph (2)) were synthesized by reaction of [Cp2MCl2] with the corresponding deprotonated amides. Complex 1a was also prepared by direct deprotonation of the amide with Schwartz reagent [Cp2Zr(H)Cl]. Salt metathesis reaction of [Cp2Zr(H)Cl] with deprotonated amide [(Dipp)N-C(Ph)O] gave the zirconocene hydrido complex [Cp2M(H){kappa(2)-N,O-(Dipp)N-C(Ph)O}] (3). Reaction of 1a with Mg did not result in the desired Zr(III) complex but in formation of Mg complex [(py)(3)Mg(Cl) {kappa(2)-N,O-(Dipp)N-C(Ph)O}] (4; py = pyridine). The paramagnetic complexes [Cp'Ti-2{kappa(2)-N,O-(R)N-C(Ph)O}] (Cp' = Cp, R = Ph (7a); Cp' = Cp, R = Dipp (7b); Cp' = Cp*, R = Ph (8)) were prepared by the reaction of the known titanocene alkyne complexes [Cp-2'Ti(eta(2)-Me3SiC2SiMe3)] (Cp' = Cp (5), Cp' = Cp* (6)) with the corresponding amides. Complexes 1a, 2, 3, 4, 7a, 7b, and 8 were characterized by X-ray crystallography. The structure and bonding of complexes 7a and 8 were also characterized by EPR spectroscopy.