Syntheses, crystal structures, and some spectrochemical properties of S-bridged tetranuclear complexes with stacking arrangements composed of planar palladium(II) units

The reaction of [Pd(aet)(2)] (aet = 2-aminoethanethiolate) with [Pd(NO3)(2)(diimine)] (diimine = 2,2'-bipyridine (bpy), 4,4'-dimethyl-2,2'-bipyridine (dmbpy), 1,10-phenanthroline (phen), 4,7-dimethyl-1,10-phenanthroline (dmphen)) gave a new type of S-bridged tetranuclear complex [{Pd(diimine)}(2){Pd(aet)(2)}(2)](4+). The crystal structures of these complexes were determined by X-ray crystallography. In these complexes, the two intramolecular diimine moieties are aligned so as to overlap each other and the PdN2S2 planes in the {Pd(aet)(2)} units are almost perpendicular to those in the {Pd(diimine)} moieties. In the case of diimine = bpy and dmbpy, furthermore, the complex cations exist in the dimeric structure with a coplanar stacking arrangement, in which the diimine moieties of the two distinct complex cations are antiparallel to each other. In the case of diimine = phen and dmphen, on the other hand, the complex cations exist in the linear-chainlike structure with an alternate coplanar stacking arrangement, in which the diimine moieties of the neighboring complex cations are antiparallel to each other. All of the complexes were characterized on the basis of the electronic absorption, diffuse reflection, and C-13 NMR spectra.