Argentophilic interactions in mono- and poly-nuclear Ag(I) complexes with N,N’-dimethyl-piperazine-2,3-dithione and iodide

A variety of silver(I) neutral complexes differing in stoichiometries and/or crystallographic arrangements have been obtained by reacting [HMe 2pipdt]I3 (1) (Me2pipdt = N,N′-dimethyl- piperazine-2,3-dithione) with silver as a metal powder and as 1+ metal ion. Once dissolved in THF, 1 reacts with silver powder, affording complexes of different ligand/metal ratios: [Ag(Me2pipdt)2]I3 (2a) and [Ag(Me2pipdt)I]2(3) (in the two different crystallographic arrangements 3a and 3b). The polymer [Ag2(Me 2pipdt)I2]n (4) and the monomer [Ag(Me 2pipdt)2]I3 (2b) are instead obtained when 1 reacts with AgSbF6 in CH3CN. The short intermetallic distances found in the dimeric and polymeric structures [d Ag-Ag(Å) = 3.3267(9) (3a), 3.0873(5) (3b), 2.8139(9)/3.1460(9)/ 3.2420(8) (4)] suggested possible argentophilic interactions in the complexes. These interactions have been investigated applying density functional theory (DFT) calculations and the atoms-in-molecules (AIM) analysis on 3a and 3b, on a fragment of 4, and on a Ag2I2 model. This model mimics the rhomboidal fragment which occurs in most of the described structures and provides the tools to ascertain the occurrence and the strength of the argentophilicity as a function of the intermetallic distance (2.7-3.5 Å) for the isolated Ag2I2 moiety. The obtained results highlight argentophilicity in 3b and 4.(Figure Presented) © 2011 American Chemical Society.