Tantalocene trihydride, or bis(η5-cyclopentadienyl)trihydridotantalum, is an organotanalum compound in the family of bent metallocenes consisting of two cyclopentadienyl rings and three hydrides coordinated to a tantalum center.

[1][2] A strong, sharp absorption band can be seen in the infrared spectra of TaCp2H3 at 1735 cm−1, which corresponds to the Ta-H bond stretching frequency.

The two cyclopentadienyl rings are in a bent conformation as confirmed by neutron diffraction studies where the ring-to-tantalum-to-ring bending angle is 139.9°.

[6] Neufeldt et al. explored the activation of aliphatic C-H bonds by TaCp2H3 and related monosubstituted cyclopentadienyl rings experimentally and computationally.

[7] The loss of another hydrogen molecule from the products can lead to β-hydride elimination, which forms complexes of the TaCp2(H)L, with L being an unsaturated π-ligand, having their own reactivity.

[8] The first phosphido derivative of tantalocene was obtained by the insertion of ClPPh2 into the Ta-H bond, resulting in the precipitation of the white ionic compound [TaCp2H2(PHPh2)]Cl.

[10] As opposed to promotion of catalysis of olefin reactions with Lewis acids like AlEt3 such as in Ziegler-Natta catalysts, triethylaluminium seems to deactivate the hydride ligand toward ethylene insertion.