Abstract
The reaction of the hexa-thia-pyrazino-phane ligand, 2,5,8,11,14,17-hexa-thia-[9.9](2,6,3,5)-pyrazino-phane (L1), with copper(II) dibromide led to the formation of a binuclear complex, [μ2-2,5,8,11,14,17-hexa-thia-[9.9](2,6,3,5)-pyrazino-phane]bis-[bromi-docopper(II)] dibromide, [Cu2Br2(C16H24N2S6)]Br2, (I). The complex possesses inversion symmetry with the pyrazine ring being situated about a center of symmetry. The ligand coordinates to the copper(II) atom in a bis-tetra-dentate manner and the copper atom has a fivefold NS3Br coordination environment with a distorted shape. The reaction of ligand L1 with copper(I) iodide also gave a binuclear complex, which is bridged by a Cu2I2 unit to form a two-dimensional coordination polymer, poly[[μ2-2,5,8,11,14,17-hexa-thia-[9.9](2,6,3,5)-pyrazino-phane]tetra-μ-iodido-tetra-copper(I)], [Cu4I4(C16H24N2S6)] n , (II). The binuclear unit possesses inversion symmetry with the pyrazine ring being located about a center of symmetry. The Cu2I2 unit is also located about an inversion center. The two independent copper(I) atoms are both fourfold coordinate. That coordinating to the ligand L1 in a bis-tridentate manner has an NS2I coordination environment and an irregular shape, while the second copper(I) atom, where L1 coordinates in a bis-monodentate manner, has an SI3 coordination environment with an almost perfect tetra-hedral geometry. In the crystal of I, the cations and Br- anions are linked by a number of C-H⋯S and C-H⋯Br hydrogen bonds, forming a supra-molecular network. In the crystal of II, the two-dimensional coordination polymers lie parallel to the ab plane and there are no significant inter-layer contacts present.
Highlights
The reaction of the hexathiapyrazinophane ligand, 2,5,8,11,14,17-hexathia[9.9](2,6,3,5)-pyrazinophane (L1), with copper(II) dibromide led to the formation of a binuclear complex, [2-2,5,8,11,14,17-hexathia-[9.9](2,6,3,5)pyrazinophane]bis[bromidocopper(II)] dibromide, [Cu2Br2(C16H24N2S6)]Br2, (I)
The complex possesses inversion symmetry with the pyrazine ring being situated about a center of symmetry
The reaction of ligand L1 with copper(I) iodide gave a binuclear complex, which is bridged by a Cu2I2 unit to form a two-dimensional coordination polymer, poly[[2-2,5,8,11,14,17hexathia-[9.9](2,6,3,5)-pyrazinophane]tetra--iodido-tetracopper(I)], [Cu4I4(C16H24N2S6)]n, (II)
Summary
Tetrasubstituted pyrazines are interesting ligands for the formation of multi-dimensional coordination polymers and metal-organic frameworks: for example, tetra-2-pyridylpyrazine (Ouellette et al, 2004; Nawrot et al, 2015) and pyrazinetetracarboxylic acid (Masci & Thuery, 2008; Zhang et al, 2014). A number of such ligands involving Npyrazine and S coordination sites have been synthesized and their coordination behaviour with transition metals investigated (Assoumatine, 1999). Ligand L2, 3,4,8,10,11,13-hexahydro-1H,6H-bis([1,4]dithiocino)[6,7-b:60,70-e]pyrazine, when reacted with CuI formed a two-dimensional coordination polymer, poly[[4-3,4,8,10,11,13-hexahydro-1H,6H-bis([1,4]dithiocino)[6,7-b:60,70-e]pyrazine]di-iodido-dicopper(I)] (Fig. 1a; Assoumatine & Stoeckli-Evans, 2020b). Ligand L3, 5,7-dihydro-1H,3H-dithieno[3,4-b:30,40-e]pyrazine, when reacted with CuI formed a three-dimensional coordination polymer, poly[(4-5,7-dihydro-1H,3H-dithieno[3,4-b:30,40-e]pyrazine-4N:N0:S:S0)tetra-3-iodidotetracopper] (Fig. 1b; Assoumatine & Stoeckli-Evans, 2020c).
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