Multinuclear copper(I) and silver(I) pyrazolates decorated with adamantyl substituents

Abstract

The synthetic details, solid-state structures, and catalytic applications of copper(I) and silver(I) complexes supported by pyrazolate ligands decorated with adamantyl groups, and the isolation of four rare, homoleptic coinage metal pyrazolate tetramers are described. Reactions of [Cu(CH₃CN)₄][BF₄] or AgNO₃ with the pyrazole [3-(Ad)-5-(iPr)Pz]H in the present of Et₃N afforded the corresponding tetranuclear copper(I) complex {[3-(Ad)-5-(iPr)Pz]Cu}₄ and trinuclear silver(I) complex {[3-(Ad)-5-(iPr)Pz]Ag}₃. Solution studies using ¹H NMR and vapor pressure osmometry suggested the presence of multiple isomers and tetranuclear state for {[3-(Ad)-5-(iPr)Pz]Cu}₄, in contrast to the singular dominant species in {[3-(Ad)-5-(iPr)Pz]Ag}₃. Using a similar synthetic method with the bulkier pyrazole [3,5-(Ad)₂Pz]H, tetranuclear complexes {[3,5-(Ad)₂Pz]Cu}₄ and {[3,5-(Ad)₂Pz]Ag}₄ have been synthesized. While the Cu4 core in {[3-(Ad)-5-(iPr)Pz]Cu}₄ adopts an approximate rhombic arrangement, the Cu4 and Ag4 cores in {[3,5-(Ad)₂Pz]Cu}₄ and {[3,5-(Ad)₂Pz]Ag}₄ feature near-square arrangements. The {[3-(Ad)-5-(iPr)Pz]Cu}₄ also functions as an excellent catalyst for the reaction between p-tolyl azide or benzyl azide and 1-octyne or phenylacetylene, affording the respective 1,4-disubstituted 1,2,3-triazoles.