η2-Iminoacyl and η2-acyl monocyclopentadienyl tantalum complexes bearing oxo and oxo-borane ligands

Abstract

Alkyl-chloro ligand exchange by the reaction of [TaCp*R2{O·B(C6F5)3}] (R = CH2Ph, Me) with Ph3CCl gave the monoalkyl compounds [TaCp*RCl{O·B(C6F5)3}] (R = CH2Ph, Me). Insertion of CNAr (Ar = 2,6-Me2C6H3) and CO into a Ta–C bond of the mono- and dialkyl complexes gave the iminoacyl compounds [TaCp*X{η2-C(R)=NAr}{O·B(C6F5)3}] (X = R = CH2Ph, Me; X = Cl, R = CH2Ph) and the acyl compounds [TaCp*X{η2-C(R)=O}{O·B(C6F5)3}] (X = R = CH2Ph, Me; X = Cl, R = CH2Ph), respectively. The related chloro compound [TaCp*Cl{η2-C(Me)=NAr}{O·B(C6F5)3}] was isolated from the reaction of the oxo derivative [TaCp*Cl{η2-C(Me)=NAr}(O)] with the Lewis acid B(C6F5)3. Addition of CNAr or pyridine to [TaCp*(CH2Ph){η2-C(CH2Ph)=NAr}{O·B(C6F5)3}] afforded the borane-free complex [TaCp*(CH2Ph){η2-C(CH2Ph)=NAr}(O)] and the acid-base adduct L·B(C6F5)3 (L = py, CNAr). The molecular structures of [TaCp*Cl{η2-C(Me)=NAr}{O·B(C6F5)3}] and [TaCp*(CH2Ph){η2-C(CH2Ph)=O}{O·B(C6F5)3}] were obtained from X-ray diffraction studies.