Synthesis of N-Heterocyclic Olefin Capped Copper Nanoparticles

Abstract

N-heterocyclic olefins (NHOs) are alkylidene counterparts of N-heterocyclic carbenes (NHCs) where a = CR2 (R: H, alkyl, aryl) group is attached to carbene carbon. Compared to NHCs, NHOs are stronger Lewis base and softer. NHC stabilized nanoparticles are synthesized mainly by reducing the NHC-metal halide complex (bottom-up) or exchanging the preformed nanoparticle's ligand with NHCs (top-down). Surprisingly, synthesis of NHC stabilized copper nanoparticles has been reported via reduction of mesitylcopper(I) with NHC-borane complex. The complex plays the role of reducing agent and as well as it provides the surface ligand, NHC, to stabilize the copper nanoparticles. In this work, we have explored the possibility of forming NHO-capped copper nanoparticles using the NHO-AlH3 complex as a reducing agent. For that, the complexation ability of IPr=CH2 with CuCl and CuBr was investigated. We have synthesized and characterized the IPr=CH2 coordinated AlH3 complex as a reagent that can generate NHO-capped copper nanoparticles by reducing mesitylcopper(I). The synthesized NHO capped copper nanoparticles were characterized using NMR, XPS, IR and DLS methods