Side-Arm Functionalized Silylene Copper(I) Complexes in Catalysis

Abstract

A convenient new method was added to the toolbox of the ligand design of N-heterocyclic silylenes and their transition-metal complexes. Herein we report on six novel compounds of two novel classes of copper(I) complexes based on the benzamidinate silylene (Cl)Si(PhC(N tBu)₂). By taming the high reactivity of the free electron pair of the Si(II) atom via a preset metalation with a desired metal precursor (in this case copper(I) halides) we can easily introduce novel pyridyl-based groups in the subsequent functionalization of the chloro group and undergo coordination of the metal atom at the same time. The resulting pseudocubane-like tetramer [XCu(I) ← (Cl)Si(PhC(N tBu)₂)]₄ 2a-2c and the trinuclear dimer [(XCu(I))₃(PyNMes)Si(PhC(N tBu)₂)] 3a-3c (with X = Cl (2a/3a), Br (2b/3b), I (2c/3c)) were fully characterized via X-ray diffraction analysis, NMR spectroscopy, mass spectrometry, and elemental analysis. Moreover, we took a look into the catalytic potential of the Cu(I) complexes 2b and 3b by testing them under the conditions of the renowned copper(I)-catalyzed alkyne-azide cycloaddition and observed an increased activity of the functionalized species.