Abstract
The reaction of the ligand 2,3,5,6-tetra-kis-[(methyl-sulfanyl)-meth-yl]pyrazine (L1) with silver(I) nitrate led to {[Ag(C12H20N2S4)](NO3)} n , (I), catena-poly[[silver(I)-μ-2,3,5,6-tetra-kis-[(methyl-sulfan-yl)meth-yl]pyrazine] nitrate], a compound with a metal-organic chain structure. The asymmetric unit is composed of two half ligands, located about inversion centres, with one ligand coordinating to the silver atoms in a bis-tridentate manner and the other in a bis-bidentate manner. The charge on the metal atom is compensated for by a free nitrate anion. Hence, the silver atom has a fivefold S3N2 coordination sphere. The reaction of the ligand 2,3,5,6-tetra-kis-[(phenyl-sulfanyl)-meth-yl]pyrazine (L2) with silver(I) nitrate, led to [Ag2(NO3)2(C32H28N2S4)] n , (II), poly[di-μ-nitrato-bis-{μ-2,3,5,6-tetra-kis-[(phenyl-sulfan-yl)meth-yl]pyrazine}disilver], a compound with a metal-organic network structure. The asymmetric unit is composed of half a ligand, located about an inversion centre, that coordinates to the silver atoms in a bis-tridentate manner. The nitrate anion coordinates to the silver atom in a bidentate/monodentate manner, bridging the silver atoms, which therefore have a sixfold S2NO3 coordination sphere. The reaction of the ligand 2,3,5,6-tetra-kis-[(pyridin-2-yl-sulfanyl)-meth-yl]pyrazine (L3) with silver(I) nitrate led to [Ag3(NO3)3(C28H24N6S4)] n , (III), poly[trinitrato{μ6-2,3,5,6-tetra-kis[(pyri-din-2-ylsulfan-yl)meth-yl]pyrazine}-trisilver(I)], a compound with a metal-organic framework structure. The asymmetric unit is composed of half a ligand, located about an inversion centre, that coordinates to the silver atoms in a bis-tridentate manner. One pyridine N atom bridges the monomeric units, so forming a chain structure. Two nitrate O atoms also coordinate to this silver atom, hence it has a sixfold S2N2O2 coordination sphere. The chains are linked via a second silver atom, located on a twofold rotation axis, coordinated by the second pyridine N atom. A second nitrate anion, also lying about the twofold rotation axis, coordinates to this silver atom via an Ag-O bond, hence this second silver atom has a threefold N2O coordination sphere. In the crystal of (I), the nitrate anion plays an essential role in forming C-H⋯O hydrogen bonds that link the metal-organic chains to form a three-dimensional supra-molecular structure. In the crystal of (II), the metal-organic networks (lying parallel to the bc plane) stack up the a-axis direction but there are no significant inter-molecular inter-actions present between the layers. In the crystal of (III), there are a number of C-H⋯O hydrogen bonds present within the metal-organic framework. The role of the nitrate anion in the formation of the coordination polymers is also examined.
Highlights
The reaction of the ligand 2,3,5,6-tetrakis[(methylsulfanyl)methyl]pyrazine (L1) with silver(I) nitrate led to {[Ag(C12H20N2S4)](NO3)}n, (I), catena-poly[[silver(I)--2,3,5,6-tetrakis[(methylsulfanyl)methyl]pyrazine] nitrate], a compound with a metal–organic chain structure
The asymmetric unit is composed of two half ligands, located about inversion centres, with one ligand coordinating to the silver atoms in a bis-tridentate manner and the other in a bis-bidentate manner
The asymmetric unit is composed of half a ligand, located about an inversion centre, that coordinates to the silver atoms in a bistridentate manner
Summary
A series of tetrakis-thioether pyrazine ligands have been prepared in order to study their coordination behaviour with various transition metals (Assoumatine, 1999). E73, 434–440 research communications tetrakis[(phenylsulfanyl)methyl]pyrazine (L2) and 2,3,5,6tetrakis[(pyridin-2-ylsulfanyl)methyl]pyrazine (L3), were synthesized by the reaction of 2,3,5,6-tetrakis(bromomethyl)pyrazine (Assoumatine & Stoeckli-Evans, 2014b), with the appropriate 2-mercapto derivative. Their crystal structures and syntheses have been reported previously: L1 (Assoumatine & Stoeckli-Evans, 2014a), L2 (Assoumatine et al, 2007) and L3 (Assoumatine & Stoeckli-Evans, 2016). The reaction of similar ligands with various silver(I) salts have resulted in the formation of coordination polymers. 2-{[(pyridin-4-ylmethyl)sulfanyl]methyl}pyrazine (Black & Hanton, 2007) led to metal–organic frameworks, while ligands 2,3-bis{[(pyridin-2-ylmethyl)sulfanyl]methyl}pyrazine (Caradoc-Davies & Hanton, 2001) and 2,5-bis{[(pyridin-2-ylmethyl)sulfanyl]methyl}pyrazine (Caradoc-Davies et al, 2001) both resulted in compounds with metal–organic chains
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