(Thio)phosphoryl-functionalized enaminoketones: Synthesis, structure, and complexing properties towards transition metal ions

P(X)-functionalized enaminoketones (X = O, S) 1a,b have been readily obtained by the condensation of o-(thio)phosphorylated anilines with sodium salt of benzoylacetaldehyde. The ligands derived exist in solution in the expected ketamino tautomeric form, but, unlike typical enaminoketones, tend to exist as cis-isomers in polar media, favored by the formation of the strong P O…HN intramolecular hydrogen bond. This six-membered hydrogen-bonded ring is also observed in the solid structure of 1a, which, nevertheless, features a trans-configuration of the enaminoketone fragment. Independent from the isomeric composition, the ligands obtained readily form κ3-X,N,O (X = O, S) complexes with a range of transition metal ions (Re(I), Pd(II), Cu(II), and Ni(II)) adopting in all cases the cis-configuration. The structures of the novel compounds are confirmed using multinuclear NMR and IR spectroscopy as well as X-ray crystallography.