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 pyz(2)SO) and a series of its metal complexes including {[Ag(pyz(2)SO)](NO(3))center dot CH(3)CN}(infinity) (1), {[Ag(pyz(2)SO)](PF(6))}(infinity) (2), [Ag(3)(pyz(2)SO)(2)(ClO(4))(3)](infinity) (3), [Ag(pyz(2)SO)(CF(3)CO(2))](infinity) (4), {[Zn(pyz(2)SO)(H(2)O)(4)](NO(3))(2)center dot H(2)O}(infinity) (5), {[Zn(pyz(2)SO)(H(2)O)(2)](ClO(4))(2)}(infinity) (6), and {[Cd(pyz(2)SO)(2)(H(2)O)](ClO(4))(2)center dot H(2)O}(infinity) (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 pi-acidic heterocyclic rings via anion-pi interactions, which consequently affect the process of supramolecular assembly. Seven distinct ligation modes of pyz(2)SO 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 pyz(2)SO ligand exhibits unusual dipolar sulfinyl center dot center dot center dot sulfinyl and S=O center dot center dot center dot pi(pyrazinyl) intermolecular interactions in the supramolecular assemblies of neat Pyz(2)SO, 1, and 3-5.