(η 5 -Carb-oxy-cyclo-penta-dien-yl)(η 7 -cyclo-hepta-trien-yl)manganese(I) hexa-fluorido-phosphate.

The title compound, [Mn(CH)(CHO)]PF or [(Cht)Mn(Cp'COH)]PF, with Cht = cyclo-hepta-trienyl and Cp' = CH, is an air-stable, purple, heteroleptic, cationic sandwich complex with manganese in oxidation state +I and π-coordinating cyclo-hepta-trienyl and cyclo-penta-dienyl ligands. The latter ligand carries the carb-oxy-lic acid functionality. This 'tromancenium-8-carb-oxy-lic acid' with hexa-fluorido-phosphate as counter-ion represents a rare case of a cationic carb-oxy-lic acid. Structurally, this organometallic carb-oxy-lic acid displays the common motif of planar O ⋯H-O /O -H⋯O hydrogen-bonded carb-oxy-lic acid dimers with -oriented metallocenyl moieties, the cationic charge of which is balanced by octa-hedrally shaped hexa-fluorido-phosphate anions. Positional disorder is observed in the cyclo-hepta-trienyl ring and the PF anion.