Dipyrazinyl Sulfoxide Complexes of Silver(I), Zinc(II), and Cadmium(II): Ligation Modes and Anion Tuning

The new ligand dipyrazinyl sulfoxide (also named sulfinyldipyrazine and abbreviated as pyz2SO) and a series of its metal complexes including {[Ag(pyz2SO)](NO3)·CH3CN}∞ (1), {[Ag(pyz2SO)](PF6)}∞ (2), [Ag3(pyz2SO)2(ClO4)3]∞ (3), [Ag(pyz2SO)(CF3CO2)]∞ (4), {[Zn(pyz2SO)(H2O)4](NO3)2·H2O}∞ (5), {[Zn(pyz2SO)(H2O)2](ClO4)2}∞ (6), and {[Cd(pyz2SO)2(H2O)](ClO4)2·H2O}∞ (7) have been synthesized and characterized by single-crystal X-ray analysis. The counteranions in these complexes prefer to be embraced by a pair of π-acidic heterocyclic rings via anion−π interactions, which consequently affect the process of supramolecular assembly. Seven distinct ligation modes of pyz2SO involving various bonding combinations of the sulfoxide oxygen and/or pyrazinyl nitrogen atoms (labeled A−G) are observed. Diverse coordination motifs such as (4,4) network, ladder-type, necklace-like, linear, and zigzag-chain structures are found in 1−7. Interestingly, the sulfoxide group of the pyz2SO ligand exhibits unusual dipolar sulfinyl···sulfinyl and SO···π(pyrazinyl) intermolecular interactions in the supramolecular assemblies of neat pyz2SO, 1, and 3−5.