Silver(I) and Mercury(II) Complexes with 1-Methyl-1,2,4-triazole as Models for Metal-Mediated Base Pairs - Formation of Discrete Complexes in Solution vs. One- and Two-Dimensional Coordination Polymers in the Solid State

The coordination chemistry of 1-methyl-1H-1,2,4-triazole (1-mtri) with respect to the linearly coordinating metal ions silver(1) and mercury(II) has been established. The ligand serves as a model nucleobase for the artificial 1,2,4-triazole nucleoside. Solution studies show that 2:1 complexes are formed with both metal ions in water. Mercury(II) forms more stable complexes than silver(I), with a stability constant of log beta(2) of 10.5 +/- 2.5 vs. 4.3 +/- 0.4 for the silver(I) complex. In the solid state, different types of cationic coordination polymars are formed. The silver complex [Ag(1-mtri)](ClO4) (1) comprises a one-dimensional coordination polymer [Ag-2-(1-mtri)(2)](n)(2n+), showing a 1:1 ratio of ligand to metal. By contrast, the mercury complex [Hg(1-mtri)(2)](ClO4)(2) (2) retains a 2:1 stoichiometry while forming a two-dimensional coordination polymer. In compound 2, mercury(II) is coordinated in a distorted octahedral fashion, with two normal and four long bonds, resulting in a compressed octahedron.