“Free” [Fe(tpp)]+ Cation: A New Concept in the Search for the Least Coordinating Anion

Ligand or solvate? This question is raised by the arrangement of the cation and two p-xylene solvent molecules in the crystal structure of 1 (shown on the right). Complex 1, which provides the first example of a [Fe(tpp)]+ cation not coordinated by the anion, shows that this question cannot be answered definitively, and introduces a new strategy for preparing weakly coordinating anions. tpp = tetraphenylporphyrinate.