(η⁵-Carboxycyclopentadienyl)(η⁷-cycloheptatrienyl)manganese(I) hexafluoridophosphate

The title compound, [Mn(C7H7)(C6H5O2)]PF6 or [(Cht)Mn(Cp'CO2H)]PF6, with Cht = cycloheptatrienyl and Cp' = C5H4, is an air-stable, purple, heteroleptic, cationic sandwich complex with manganese in oxidation state +I and π-coordinating cycloheptatrienyl and cyclopentadienyl ligands. The latter ligand carries the carboxylic acid functionality. This `tromancenium-8-carboxylic acid' with hexafluoridophosphate as counter-ion represents a rare case of a cationic carboxylic acid. Structurally, this organometallic carboxylic acid displays the common motif of planar Osp 2...H—Osp 3/Osp 3—H...Osp 2 hydrogen-bonded carboxylic acid dimers with anti-oriented metallocenyl moieties, the cationic charge of which is balanced by octahedrally shaped hexafluoridophosphate anions. Positional disorder is observed in the cycloheptatrienyl ring and the PF6 − anion.