Konkurrierende Liganden: Theophyllin als nicht- und stark koordinierender Ligand in Quecksilber(II)-Komplexen / Competing Ligands: Theophylline as Non- and Strongly Coordinating Ligand in Mercury(II) Complexes

Abstract

[{Hg(CF3)2}(ThpH)(H2O)](H2O) (1), [{Hg4(Thp)4}(ClO4)4(H2O)8](H2O)4 (2), [{Hg(ThpH)2} (NO3)](NO3) (3) and {Hg(Thp)Cl}(H2O) (4) (ThpH = theophylline, C7H8N4O2) have been synthesized by slow evaporation of aqueous solutions of the mercuric salts Hg(CF3)2, Hg(ClO4)2, Hg(NO3)2, or HgCl2 and theophylline. Their crystal structures were determined on the basis of single crystal X-ray data. The coordination polymers 1 and 2 crystallize with triclinic symmetry, P1̅ (no. 2), with a = 468.8(2), b = 1256.4(5), c = 1445.5(6) pm, α = 67.15(3), β = 89.21(3), γ = 89.40(3)° and a = 833.6(1), b = 1862.7(2), c = 2182.9(2) pm, α = 111.61(1), β = 90.98(1), γ = 95.51(1)°, respectively. 3 and 4 crystallize with monoclinic symmetry, Pc (no. 7), a =1194.1(1), b=1258.8(2), c=735.5(2) pm, β =96.96(2)° and P21/n (no. 14), a=1069.0(2), b =911.6(1), c=1089.9(2) pm and β = 96.87(2)°. In 1 the theophylline molecules are non-coordinating to mercury and leave the Hg(CF3)2 molecule unchanged. Only weak electrostatic attractions to one keto-oxygen atom of theophylline and one water molecule hold this co-crystallisate together. In 2, the theophyllinate anion, Thp−, strongly coordinates with both N(7) and N(9) to HgII forming a large ring with eight Hg atoms that incorporates the water molecules. One sort of nitrate ions in 3 is weakly attached to HgII with the theophylline molecules still bound strongly through N(9). The chloride ligand and the theophyllinate ion seem to have the same strengths as ligands in 4 as they are both attached to HgII with the shortest distances possible