Unexpected isomerism in "[Pd(2,9-dimethylphenanthroline)X2]" (X = Cl, Br, I) complexes: a neutral and an ionic form exist.

Complexes of composition "[Pd(2,9-dimethylphenanthroline)X(2)]" (X = Cl, Br, I) have long been known and they are used as precursors for the synthesis of other derivatives or as catalysts. In the previous literature, they have invariably been described as neutral square planar complexes, but we have found that a second ionic isomer also exists, having composition [Pd(Neoc)(2)X](2)[Pd(2)X(6)], and that the formation of this isomer occurs under a wider range of conditions than that of the neutral one. Retrospectively, the ionic isomer had surely been obtained in most previous reports even if formation of the neutral one was claimed.