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

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.