“Click” Immobilization of Organometallic Pincer Catalysts for C−C Coupling Reactions

Abstract

Model systems for the simple, high-yielding, efficient “click” immobilization of homogeneous pincer catalysts are demonstrated. We present the synthesis of azide- and isocyanate-functionalized high pore volume, low surface area silica materials. Both para-ethynyl-functionalized palladium and platinum pincer organometallics (pincer = [C6H3(CH2NMe2)2-2,6]−) were coupled with azido-functionalized silica material, yielding the corresponding tethered complexes in high yields with no complex degradation. Analogous para-alcohol-functionalized palladium and platinum pincer complexes were coupled with isocyanate-functionalized silica material to yield immobilized organometallics in high yields. The acquired immobilized organometallic pincer complexes were characterized using various techniques (solid-state IR and NMR, elemental content analysis, surface area measurements). Palladium-containing materials were applied as Lewis acid catalysts in the double Michael addition reaction between ethyl cyanoacetate and meth...