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 NiIIatoms that are arranged in a triangular fashion along with five supporting ligands. There are two square-planar NiIIatoms and a third pseudo-octahedral NiIIatom. While the square-planar NiIIatoms are stacked, there are no ligand bridges between them. Each square-planar NiIIatom, however, bridges with the pseudo-octahedral NiIIatom 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 NiIIatoms. The proton-bridged complex completes the macrocyclic coordination around the square-planar NiIIatoms 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 thecaxis. 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].