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

Article abstract of DOI:10.1039/b307306h

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, CH ₂[CH(pz^4Et)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-CH ₂[CH(pz^4Et)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(pz^4Et)]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(NO ₃)₄]^- anion in solution.