Synthesis of the silver(i) complex of CH2[CH(pz4Et)2]2containing the unprecedented [Ag(NO3)4]3−anion: A general method for the preparation of 4-(alkyl)pyrazoles

Abstract

A general two-step method for the syntheses of 4-(alkyl)pyrazoles has been developed. The first step involves the reaction between organyl diethylacetals and the Vilsmeier reagent to give a mixture of ethoxy- and dimethylamino- acroleins. This mixture reacts directly with hydrazine monohydrogenchloride to yield the desired (4-substituted)pyrazoles. The 4-(phenyl)pyrazole derivative exhibited a markedly lower solubility in common organic solvents. In the solid state structure the phenyl and pyrazolyl groups are nearly coplanar and extensive intermolecular CH–π interactions organize the molecules in two-dimensional sheets that are held in a three dimensional arrangement by NH⋯N hydrogen bonds. Tetrakis[(4-ethyl)pyrazolyl]propane, CH2[CH(pz4Et)2]2, was prepared by a transamination reaction and reacts with Ag(NO3) to yield a compound with a 4 ∶ 3 metal ∶ ligand mole ratio that when crystallized by diffusion of Et2O into an acetone solution produced [Ag2{μ-CH2[CH(pz4Et)2]2}2]3[Ag(NO3)4]2 (1). This complex contains dimeric units in which two silver cations are sandwiched between two CH2[CH(pz4Et)]2 ligands and the counterion is the unprecedented tetra(nitrato)argentate anion. ESI mass spectral data support the existence of both the cationic dimeric units and the [Ag(NO3)4]− anion in solution.