Reaction of one equivalent of tris(3,5-di-tert-butyl-2-hydroxy)methane with TaCl₅ in CH₂Cl₂ along with Et₃N gave a solid which on prolonged crystallisation led to a small quantity of crystalline material. An X-ray crystal structure determination showed one crystal was {TaCl₃[{OC₆H₂(CMe₃)₂-2,4}₃CH]}⁻ Et₂NH₂⁺·3C₆H₆·1.5H₂O with the anion consisting of three chloro ligands and three phenoxides of the tripodal ligand about the tantalum centre. The triphenylmethyl group proton was located and refined and was found to be enclosed in a cage making contacts of 2.09(8), 2.09(8) and 1.89(12) Å with the phenoxide ligand oxygens consistent with weak C–H bond hydrogen bonding. The hydrogen atom points at the tantalum atom at a distance of 2.14(11) Å from it, the Ta⋯H–C angle is 166° and the C–H bond distance is 1.04(12) Å. DFT calculations at the B3LYP level indicate that where a hydrogen atom is attached to the triphenylmethyl carbon on the inside of the cage, there is good agreement with the crystal structure. The C–H bond points directly at the tantalum centre and an NBO analysis indicates there is significant overlap of the triphenylmethyl C–H bond electron density in a linear sense with an “unfilled” metal d orbital. Based on the NBO analysis, the C–H⋯Ta overlap would appear to be an example of a linear agostic interaction under the definition of agostic bonding.