Lewis-base adducts of Group 1B metal(I) compounds. Part 5. Synthesis and crystal structures of adducts of silver(I) thiocyanate with 2- and 3-methylpyridine, 2,6-dimethylpyridine, and quinoline

Abstract

The crystal structures of the title compounds [{Ag(SCN)L}_n][L = 2-methylpyridine (1), 3-methylpyridine (2), or 2,6-dimethylpyridine (3)] and [{Ag(SCN)L₂}_n][L = quinoline (4)] have been established by single-crystal X-ray diffraction methods at 295(1) K and refined by least squares to residuals of 0.061, 0.046, 0.055, and 0.031 for 1 139, 1 478, 956, and 2 399 independent ‘observed’ reflections respectively. Crystals of (1) are orthorhombic, space group Pn2₁a, with a= 18.350(5), b= 11.209(3), c= 4.180(1)Å, and Z= 4; the structure is an infinite two-dimensional polymer parallel to bc, with silver atoms pseudo-tetrahedrally four-co-ordinated by the sulphur and nitrogen atoms of bridging thiocyanate groups [Ag–S, 2.552(3) and 2.637(3); Ag–N, 2.27(1)Å] and by the 2-methylpyridine [Ag–N, 2.34(1)Å]. There is some disorder. Crystals of (2) are orthorhombic, space group Pbca, with a= 18.055(8), b= 11.385(5), c= 8.404(4)Å, and Z= 8. The structure is an infinite two-dimensional polymer parallel to bc with silver atoms pseudo-tetrahedrally four-co-ordinated by the sulphur and nitrogen atoms of the bridging thiocyanate groups [Ag–S, 2.578(2) and 2.615(2); Ag–N, 2.293(5)Å] and by the 3-methylpyridine [Ag–N, 2.331(5)Å]. Crystals of (3) are monoclinic, space group P2₁/c, with a= 8.481(3), b= 8.102(2), c= 13.676(7)Å, β= 97.41 (3)°, and Z= 4. The structure is a one-dimensional polymer generated by the 2₁ screw along b; the silver atom is three-co-ordinated by sulphur and nitrogen atoms of the bridging thiocyanate ligand [Ag–S, 2.474(3); Ag–N, 2.28(1)Å] and by the 2,6-dimethylpyridine ligand [Ag–N, 2.275(8)Å]. The change in co-ordination number in the latter complex is attributable to the increased steric bulk of the 2,6-dimethylpyridine ligand compared to the monosubstituted analogues. Crystals of (4) are orthorhombic, space group P2₁2₁2₁, with a= 15.977(4), b= 13.544(4), c= 8.009(2)Å, and Z= 4. The structure is the first established for a silver halide/pseudo-halide–nitrogen base complex with 1 : 2 stoicheiometry. It is a one-dimensional polymer generated by the 2₁screw along c, with four-co-ordinate pseudo-tetrahedral silver atoms linked by S, N-bridging thiocyanate groups [Ag–S, 2.495(1); Ag–N, 2.332(5)Å]. The remaining two co-ordination sites of the silver are filled by quinoline nitrogen atoms [Ag–N, 2.364(3) and 2.361 (4)Å].