Trapping Unstable Terminal Ta−O Multiple Bonds of Monocyclopentadienyl Tantalum Complexes with a Lewis Acid

Hydrolysis of Ta−Cl or Ta−C bonds with the
water-coordinated adduct [H2O·B(C6F5)3] allowed the
synthesis of borane-stabilized complexes [TaCp*R2{O·B(C6F5)3}] (R = Cl, CH2Ph, Me) with a tantalum−oxo
multiple bond. The chloro derivative in the presence of
pyridine releases the adduct [py·B(C6F5)3] with formation of the oxo-bridged compound [TaCp*Cl2(μ-O)]2. DFT
calculations have been carried out to determine the
electronic properties of the Ta−O and O−B bonds.