Bis(benzonitrile)palladium(II) Dihalides:  Structures and Cocrystallization of the Cubic Cluster Pd6Cl12 with (E)-Stilbene and with Bis(benzonitrile)palladium(II) Dichloride

Crystals of the planar, trans complexes, bis(benzonitrile)palladium(II) dichloride and bis(benzonitrile)palladium(II) dibromide, suitable for single-crystal X-ray diffraction studies are obtained by growth from solutions in benzonitrile and their structures determined. While bis(benzonitrile)palladium(II) dichloride readily loses benzonitrile to form the cubic cluster Pd6Cl12, which cocrystallizes with a variety of planar aromatic hydrocarbon molecules, the much less soluble complex bis(benzonitrile)palladium(II) dibromide does not act as a source of the so far unknown cluster Pd6Br12. Attempts to prepare the hypothetical bis(benzonitrile)palladium(II) diiodide by reaction of PdI2 with benzonitrile were not successful. A solution of bis(benzonitrile)palladium(II) dichloride in p-xylene on standing produces crystals of Pd6Cl12·(PhCN)2PdCl2·p-xylene, which contain columns of alternating Pd6Cl12 and (PhCN)2PdCl2 molecules in face-to-face orientations along with similar columns in which Pd6Cl12 and p-xylene molecules are interleaved in face-to-face arrays. A solution of bis(benzonitrile)palladium(II) dichloride and (E)-stilbene in benzene solution leads, not to coordination of palladium to the olefin, but to deposition of crystals of the ternary molecular compound, Pd6Cl12·0.5((E)-stilbene)·2(benzene). In this solid, two Pd6Cl12 clusters make face-to-face contact with phenyl rings on opposite sides of the (E)-stilbene molecule, but the olefinic portion is far from the palladium cluster. Additionally, one of the two benzene rings abuts the Pd6Cl12 cluster in a face-to-face fashion.