2,2′-Ethylenebis(1,3-dithiane) as a polydentate μ2-, μ4- and μ5-assembling ligand for the construction of sulphur-rich Cu(i), Hg(ii) and heterometallic Cu(i)/Hg(ii) coordination polymers featuring uncommon network architectures

Abstract

With the aim to elaborate novel and inexpensive sulphur-rich materials featuring unusual network architectures, the coordination chemistry of the tetradentate thiaheterocycle 1,2-di(1,3-dithian-2-yl)ethane L1 ligand toward CuX and HgX₂ salts was investigated. When L1 is reacted with CuI in a 1 : 1 ratio, a two-dimensional CP [{Cu(μ₂-I)₂Cu}(μ₂-L1)]_n (CP1) is formed, in which two out of four S atoms of L1 remain non-coordinated. Upon treatment of L1 with CuI in a 1 : 2 ratio, [{Cu(μ₂-I)₂Cu}(μ₄-L1)]_n (CP2) is obtained, in which each S atom of L1 coordinates to one copper centre forming a 2D layer. Raising the ligand-to-CuI ratio to 1 : 4 affords the 2D material [{Cu(μ₄-I)(μ₂-I)Cu}₂(μ₄-L1)]_n (CP3), in which [Cu(μ₄-I)(μ₂-I)Cu]_n ribbons are interconnected through μ₄-bridging L1 ligands. Upon the reaction of L1 with CuBr in a 1 : 2 ratio, a 2D CP [{Cu(μ₂-Br)}₂(μ₂-L1)(μ₄-L1)_0.5]_n (CP4) is formed at room temperature and a 2D CP [{Cu(μ₂-Br)}₂(μ₄-L1)]_n (CP5) is obtained in refluxing propionitrile. In CP4 and CP5 Cu atoms are bridged by a single μ₂-Br ligand giving rise to [Cu(μ₂-Br)Cu]_n ribbons but CP4 differs from CP5 from the metal to ligand ratio and the presence of non-coordinated S atoms. Employing a 1 : 3 ratio, a 1D ribbon [{Cu(μ₂-Br)}₃(MeCN)(μ₄-L1)]_n (CP6) is generated, that contains both tetrahedral and trigonal copper atoms. CP6 also presents two different L1 ligands that differ by the coordination mode of the sulphur atoms (S acting as 2 or as 4 electron-donor). With CuCl, a 2D network [{Cu(μ₂-Cl)₂Cu}(μ₄-L1)]_n (CP7) is generated. L1 coordinates also on HgX₂ salts to yield CPs whose architecture depends on the ligand-to-metal ratio. The meander-shaped 1D CP [(HgI₂)(μ₂-L1)]_n (CP8) and the linear 1D ribbons of CP9 and CP12 [(HgX₂)(μ₂-L1)]_n (X = Br, Cl) result from treatment with L1 in a 1 : 1 ratio. In the case of HgBr₂, using a 2 : 1 metal-to-ligand ratio, 1D polymeric [{BrHg(μ₂-Br)₂HgBr}(μ₂-L1)] (CP10) is produced. HgI₂ and HgBr₂ have also been reacted with 2-methyl-1,3-dithiane L2 yielding the molecular complexes [{IHg(μ₂-I)₂HgI}(κ¹-L2)₂] (D1) and [HgBr₂(κ¹-L2)₂] (M1). Two heterometallic 1D materials [{IHg(μ₂-I)₂HgI(μ₂-I)₂{Cu(RCN)₂}₂(μ₂-L1)]_n (CP13) and (CP14) result from the treatment of CP1 with HgI₂ in MeCN or EtCN. Performing the reaction of CP1 with HgBr₂ in acetonitrile produces the zwitterionic 2D material [Cu(MeCN)}(HgIBr₂)(μ₂-L1)_1.5]_n (CP15).