In-house and synchrotron X-ray diffraction studies of 2-phenyl-1,10- phenanthroline, protonated salts, complexes with gold(III) and copper(II), and an orthometallation product with palladium(II)

Different salts of the 2-phenyl-1,10-phenanthrolin-1-ium cation, (pnpH)⁺, are obtained by reacting 2-phenyl-1,10-phenanthroline (pnp), C₁₈H₁₂N₂, (I), with a variety of anions, such as hexafluoridophosphate, C₁₈H₁₃N₂⁺ PF6^-, (II), trifluoromethanesulfonate, C₁₈H ₁₃N₂⁺ CF₃SO₃^-, (III), tetrachloridoaurate, (C₁₈H₁₃N₂) [AuC_l4], (IV), and bromide (as the dihydrate), C₁₈H ₁₃N₂⁺ Br^- 2H₂O, (V). Compound (I) crystallizes with Z' = 2, with both independent molecules adopting a coplanar conformation. In (II)-(IV), a hydrogen bond exists between the cation and anion, while one of the lattice water molecules serves as a hydrogen-bonded bridge between the cation and anion in (V). Reaction of (I) with HAuC _l4 gives the salt complex (IV); however, reaction with KAuC _l4 produces the monodentate complex trichlorido(2-phenyl-1,10- phenanthroline-κN¹⁰)gold(III), [AuCl₃(C ₁₈H₁₂N₂)], (VI). Dichlorido(2-phenyl-1,10- phenanthroline-κ² N,N')copper(II), [CuCl₂(C ₁₈H₁₂N₂)], (VII), results from the reaction of CuCl₂ 2H₂O and (I), in which the Cu^II center adopts a tetrahedrally distorted square-planar geometry. The pendent phenyl ring twists to a bisecting position relative to the phenanthroline plane. The square-planar Pd^II complex, bromido[2-(phenanthrolin-2-yl)phenyl- κ³ C¹,N,N']palladium(II), [PdBr(C₁₈H ₁₁N₂)], (VIII), is obtained from the reaction of (I) with [PdCl₂(cycloocta-1,5-diene)], followed by addition of bromine. A coplanar geometry for the pendent ring is adopted as a result of the tridentate bonding motif.