o-Nitrophenylpalladium(II) complexes. Crystal and molecular structures of cis-[Pd{o-C6H4N(O)O}2] and cis-[Pd{o-C6H4N(O)O}(o-C6H4NO2)(py)]

Abstract

Bis(o-nitrophenyl)mercury reacts with palladium dichloride in molar ratios of 2 : 1 or 1 : 1 to give cis-[[graphic omitted]}₂] or [{[graphic omitted]](µ-Cl)}₂], respectively. The first product reacts with some unidentate (L) or bidentate (L–L) ligands to give [[graphic omitted]}(o-C₆H₄NO₂)L][L = Ph₃PCHCO₂Me, pyridine (py), 3-bromopyridine, or 4-cyanopyridine] or [Pd(o-C₆H₄NO₂)₂-(L–L)][L–L = 1, 10-phenanthroline, 2,2′-bipyridine, 1,2-bis(diphenylphosphino)ethane, or bis-(diphenylphosphino)methane] or with PdCl₂, Cl₂, PhlCl₂, or HgX₂ to give [{[graphic omitted]]-(µ-X)}₂](X = Cl or Br). The chloro complex reacts (i) with unidentate ligands L (molar ratio 1 : 2) to give [{Pd(o-C₆H₄NO₂)L(µ-Cl)}₂](L = PPh₃ or AsPh₃), (ii) with cyclo-octa-1,5-diene (cod) to give [Pd(o-C₆H₄NO₂)Cl(cod)], and (iii) with thallium acetylacetonate, Tl(acac), to give [[graphic omitted]}(acac)]. The crystal structure of cis-[[graphic omitted]}₂] consists of molecules, with square-planer co-ordination, stacked parallel to the (001) plane with alternate Pd ⋯ Pd distances of 3.465(1) and 3.209(1)Å. The Pd–C [2.033(5)Å(av.)] and Pd–O [2.144(14)Å(av.)] bond lengths are normal, while the C–N [1.390(4)Å(av.)] are shorter than those found in unidentate nitroaryl ligands. The structure of [[graphic omitted]}(o-C₆H₄NO₂)-(py)] shows a square-planar co-ordination around the palladium atom with a cis configuration of the phenyl groups. The only significant differences between both types of o-nitrophenyl ligands are shorter C–N [1.428(6)Å] and longer N–O(Pd)[1.265(5)Å] bond distances in the chelating than in the unidentate ligand [1.464(5) and 1.222(5)(av.)Å, respectively].