Preparation and characterization of the 1:1 adducts of mercury(II) halides with N-benzyl- and N-p-tolyl-2-oxo-1-naphthylideneamine. The crystal and molecular structures of two isostructural di-μ-halo-bis[halo(N-benzyl-2-oxo-1-naphthylideneamine)mercury(II

A series of adducts of the type HgX2(C18H15NO) [X=Cl−, Br−, I−; C18H15NO=N-benzyl-2-oxo-1-naphthylideneamine (bznapH), N-p-tolyl-2-oxo-1-naphthylideneamine (tolnapH)] was obtained by refluxing the solution of the corresponding mercury(II) salt and the related naphthylideneamine in absolute ethanol in a 1:1 molar ratio. The adducts di-μ-chloro-bis[chloro(N-benzyl-2-oxo-1-naphthylideneamine)mercury(II)], HgCl2(bznapH) (1) and di-μ-bromo-bis[bromo(N-benzyl-2-oxo-1-naphthylideneamine)mercury(II)], HgBr2(bznapH) (2) are isostructural with the effective coordination of mercury being 2+2. The HgX2 moieties are retained in the adducts and contain two covalently linked chlorine [2.321(3) and 2.299(3) Å in 1] or bromine atoms [2.446(1) and 2.422(1) Å in 2]. These moieties are linked mutually by additional contacts of bridging halogen atoms [Hg⋯μX 3.189(2) and 3.298(1) Å in 1 and 2, respectively], forming non-planar dimeric Hg2X4 units. Each Schiff-base ligand has a strong contact with mercury through the oxygen atom [Hg⋯O 2.392(5) and 2.410(5) Å in 1 and 2, respectively]. The Schiff-base ligand in 1 and 2 exists as the ketoamino (quinoid) tautomeric structure with an intramolecular hydrogen bond of the NH⋯O type [2.58(1) and 2.59(1) Å in 1 and 2, respectively]. On the contrary, in DMSO solution, due to dissociation of adducts 1–6, the enolimino (benzenoid) tautomeric form of the Schiff bases was established by NMR spectroscopy.