Functional nickel complexes of N-heterocyclic carbeneligands in pre-organized and supported thin film materials

Abstract

Nickel(II) complexes with double alkyl chain functionalized N-heterocyclic carbene (NHC) ligands, [NiCl₂(C₁₂MIM)₂] and [NiCl₂(C₁₂C₁₂IM)₂], where C₁₂MIM = 1-dodecyl-3-methylimidazolin-2-ylidene (1) and C₁₂C₁₂IM = 1,3-didodecylimidazolin-2-ylidene (2), have been prepared and fully characterized by ¹H NMR, ¹³C NMR, and CHN elemental analyses. Furthermore, we have developed a system, in which double long alkyl chain derivatized Ni–NHC complexes are dissolved in the related ionic liquid crystalline 1,3-didodecylimidazolium tetrafluoroborate, [C₁₂C₁₂IM][BF₄], to form pre-organized structures for enhanced reactivity. Remarkably, differential scanning calorimetry, polarized optical microscopy, and temperature-programmed IR reflection absorption spectroscopy performed on a mixture of 10 wt% Ni complexes in [C₁₂C₁₂IM][BF₄] demonstrate that this system retains an ionic liquid crystalline phase; even after immobilization onto a silica-100 support with pore filling α = 1.