Synthesis and structural characterization of bis-chelate Pd(II) complexes derived from substituted di-(2-pyridyl)methane ligands

Abstract

Bis-chelate complexes of palladium(II) derived from dipyridyl ligands of general formula [Pd(L)2](BF4)2 (L=(C5H4N)2C(OH)2, (C5H4N)2CH(OH), (C5H4N)2CH(Cl), (C5H4N)2CH(S2CNEt2) and (C5H4N)2CH(S-C5H4N)) have been synthesized and characterized by elemental analyses, X-ray diffraction, vibrational, and NMR spectroscopy. Crystal structures of the complexes [bis-{di-(2-pyridyl)dihydroxymethane}palladium(II)]tetrafluoroborate (1), [bis-{di-(2-pyridyl)hydroxymethane}palladium(II)]tetrafluoroborate (2), [bis-{di-(2-pyridyl)chloromethane}palladium(II)]tetrafluoroborate (3), [bis-{di-(2-pyridyl)-N,N′-diethyldithiocarbamatemethane}palladium(II)]tetrafluoroborate (4) and [bis-{di-(2-pyridyl)-2-pyridylsulfanylmethane}palladium(II)]tetrafuoroborate (5) displayed to the substituted di-2-pyridylmethane ligands in a bidentate coordination mode to the palladium atom with the formation of six-membered chelate rings. In these complexes, the palladium atom showed a distorted square planar local geometry. Crystal structures of the complexes 3–5 displayed the –Cl, –S2C(NEt)2 and –S-C5H4N groups on the bridge carbon atom in a flagpole position, which is stabilized by weak intramolecular interactions of type Pd⋯Cl (for 3) and Pd⋯S (for 4 and 5). However, in 2 the crystallographic data showed to the major conformer containing the –OH group in a bowsprit position, displaying an intramolecular Pd⋯H interaction.