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Solid state structures of 2, 4, 5b, and 6. Thermal ellipsoids set at 50%. For clarity, hydrogen atoms as well as the [Na(12-crown-4)2]+ counterion and an unbound diethylether molecule in structure 5b are omitted. Only the main component of a disordered isopropyl group in 2 and only one of the two independent molecules of 6 are plotted.
