Pyridine-2-thione and pyrimidine-2-thione derivatives of silver(I): Synthesis and structures of unusual dinuclear and polynuclear coordination compounds, [Ag2Cl2(pytH)2(dppm)], [Ag2Br2(pymtH)(PPh3)3] and {AgCl (pytH)2}n

The chemical reactivity of heterocyclic-2-thiones towards silver halides in presence of donor ligands, such as tertiary phosphines, is poorly explored relative to that with other anions (such as NO3, OAc etc). It was observed in a research report that chemical reactivity of silver(I) chloride/bromide with pyridine-2-thione (pytH) in the presence of a tertiary phosphine, was different in terms of nuclearity. In this manuscript some unusual products from reactions of silver(I) halides with pyridine-2-thione (pytH)/pyrimidine-2-thione (pymtH) in presence of tertiary phosphines are reported. In one case, reaction of a bis(diphenylphosphino)methane (dppm) with silver(I) chloride yielded a crystalline product of stoichiometry, [Ag2Cl2)(pytH)2(mu -P,P-Ph2PCH2PPh2)] 1. Silver(I) chloride with pytH in the presence of tri-p-tolylphosphine ligand did not form the expected, AgCl(pytH)(p-tolyl3P)2 complex, rather it has formed a compound of stoichiometry, {AgCl(pytH)2} 2. The crystal structures of these compounds revealed the formation of a triply bridged di-nuclear compound, [(x1Cl)Ag(mu -Cl)(mu -P,PPh2PCH2PPh2)(mu -S-pytH)Ag(x1S-pytH)] 1, and a polymeric product, {AgCl(x1S-pytH)(mu -S-pytH)-}n, 2, respectively. The chemical reactivity of pyrimidine-2-thione (pymtH) is found to be different. A reaction of silver(I) bromide with PPh3 and pymtH, yielded a bromo-bridged unsymmetrical dinuclear compound, [(PPh3)2Ag (mu -Br)2Ag(PPh3)(x1S-pymtH)] 3. Reaction of AgNO3 with pytH and PPh3 in the presence of Et3N base did not yield the expected [Ag(x1S-pyt)(PPh3)3] compound, rather it formed the ionic complex, [Ag(x1S-pytH)(PPh3)3] (NO3)& sdot;CH3OH & sdot;0.25H2O 4. In compound 1, there is a short Ag & sdot;& sdot;& sdot;Ag distance of 3.1127(3) & Aring;, suggesting possibility of argentophillic interaction.