Trinuclear nickel coordination complexes of phenanthrene-9,10-dione dioxime

Abstract

A trinuclear nickel complex of phenanthrene-9,10-dione dioxime (H2pqd), namely bis[μ2-9,10-bis(oxidoimino)phenanthrene]bis[μ2-10-(oxidoimino)phenanthrene-9-one oxime](phenanthrene-9,10-dione dioxime)trinickel(II) toluene disolvate, [Ni3(C14H8N2O2)2(C14H9N2O2)2(C14H10N2O2)]·2C7H8, has been isolated and its crystal structure determined. This complex features three independent NiII atoms that are arranged in a triangular fashion along with five supporting ligands. There are two square-planar NiII atoms and a third pseudo-octahedral NiII atom. While the square-planar NiII atoms are stacked, there are no ligand bridges between them. Each square-planar NiII atom, however, bridges with the pseudo-octahedral NiII atom through Ni—N—O—Ni and Ni—O—Ni bonds. A fluoridoboration reaction of the proton-bridged species gave the analogous complex bis(μ2-bis{[10-(oxidoimino)-9,10-dihydrophenanthren-9-ylidene]amino}difluoridoborato)(phenanthrene-9,10-dione dioxime)trinickel(II) dichloromethane trisolvate, [Ni3(C28H16BF2N4O2)4(C14H10N2O2)]·3CH2Cl2, which shows the same binding structure, but features a widened Ni—Ni interaction between the square-planar NiII atoms. The proton-bridged complex completes the macrocyclic coordination around the square-planar NiII atoms by means of an O—H...O hydrogen bond. Both compounds feature O—H...N hydrogen bonds between the oxime and the N atoms attached to square-planar nickel atom. The nickel units show no direct interaction with their nearest neighbors in the extended lattice. Two π-stacking interactions between adjacent molecules are found: one with a centroid–centroid distance of 3.886 (2) Å and the other with a centroid–centroid distance of 4.256 (3) Å. In the latter case, although not aromatic, the distance to the centroid of the central phenanthrene ring is shorter, with a distance of 3.528 (3) Å. Toluene molecules occupy the solvent channels that are oriented along the c axis. In the fluoridoboronate structure, the solvent (DCM) was too badly disordered to be modelled, so its contribution was removed using SQUEEZE [Spek (2015). Acta Cryst. C71, 9–18].

Keywords

• crystal structure
• nickel
• H2pqd
• α–β dioxime
• trinuclear
• hydrogen bonding