Hemilabile silver(i) complexes containing pyridyl chalcogenolate (S, Se) ligands and their utility as molecular precursors for silver chalcogenides

Abstract

A series of silver triphenylphosphine complexes containing pyridyl chacogenolate (S, Se) ligands has been synthesized by employing [AgCl(PPh₃)₃] and [Ag₂(μ-Cl)₂(PPh₃)₄]. The complexes [Ag(S-4-pyH_0.5)₂(PPh₃)₂] (1) and [Ag₂(μ-S-4-py)₂(PPh₃)₄] (2) were obtained by the reactions of [Ag₂(μ-Cl)₂(PPh₃)₄] with 4-pySH in the presence of Et₃N and NaOH, respectively. The former has a hydrogen-bonded chain-like structure, while the latter possesses a discrete binuclear structure. 2 on heating in methanol afforded a two-dimensional coordination polymer, [Ag₂(μ-S-4-py)₂(PPh₃)₂]_n (3). The reaction of [Ag₂(μ-Cl)₂(PPh₃)₄] with NaSe-4-py gave [Ag₃(μ-Se-4-py)₃(PPh₃)₄] (4) as the primary product together with a minor mononuclear complex, [Ag(Se-4-py)(PPh₃)₃] (5). The latter could be obtained in excellent yield under the same conditions utilising [AgCl(PPh₃)₃] as the starting material. Complex 5 on recrystallization afforded 4. The reaction of [AgCl(PPh₃)₃] with NaS-2-py yielded [Ag(S-2-py)(PPh₃)₃] (6). Complexes 2–6 on refluxing in chloroform gave insoluble polymeric complexes of composition [Ag(Epy)]_n (7) (Epy = 4-pyS (7a), 4-pySe (7b), 2-pyS (7c)) which on thermolysis yielded Ag₂E (E = S, Se). The molecular structures of these complexes (1–6) have been established unambiguously by single-crystal X-ray diffraction analyses. Non-bonding interactions in the molecular structures have been discussed.