Bridging vs. Chelating Coordination Modes of Vinylsilanes in CuI π-Complexes: Structure and Stability


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Two new copper(I) olefin complexes, [Cu6Cl6(MTrVS)2] (1) and [Cu2Cl2(DMVSP)2] (2), of tridentate bridging methyltrivinylsilane (MTrVS) and bidentate chelating 2-[dimethyl(vinyl)silyl]pyridine (DMVSP) have been synthesized and characterized by single-crystal X-ray structure analysis, IR and 1H NMR spectroscopy. It has been shown that using the alkenylsilanes with required electronic properties, molecular symmetry and conformational flexibility, it is possible to control the formation of optimal copper(I) halide oligomers. The obtained results, together with relevant literature data, also illustrate how the coordination mode of vinylsilanes is related to Cu–(C=C) bond strengthening and, consequently, to stability of the organometallic compounds. In particular, we suggest that, together with Cu–Cα distance shortening accompanied by a segmentation of π-conjugated chelate ring, complex shows an increased lability to form probably an alkenylcopper intermediate in the homocoupling reaction of alkenyl(2-pyridyl)silanes. At the same time, no appreciable reduction of thermal stability of π-conjugated chelate complex 2 with respect to bridged compound 1 emerges.