Abstract

The organometallic dicarboxylic acid cation [(η⁵-C₅H₄COOH)₂Co]⁺ crystallises with the dihydrogen phosphate acid anion [H₂PO₄]⁻ from water to form the hydrated crystal [(η⁵-C₅H₄COOH)₂Co]⁺[H₂PO₄]⁻·H₂O (1), and with its zwitterionic form, one anion [H₂PO₄]⁻ and two neutral acid H₃PO₄ molecules to form the anhydrous co-crystal [(η⁵-C₅H₄COOH)₂Co]⁺[H₂PO₄]⁻·[(η⁵-C₅H₄COOH)(η⁵-C₅H₄COO)Co]·2[H₃PO₄] (2), which can also be formulated as 2{[(η⁵-C₅H₄COOH)₂Co]⁺[H₂PO₄]⁻}·[H₃PO₄], because of the competition in the possession of the proton in the O–H⋯O hydrogen bond between the organometallic and inorganic moieties.