John C Johnson, Yuzhong Wang, Claire Buck, Pingrong Wei, Mitchell E Lahm, Henry F Schaefer, Gregory H Robinson
Room-temperature reaction of the imidazole-based dithiolate dimer (1) with hexachlorodisilane (Cl3Si-SiCl3) in toluene affords 2a chiral hexathiadisila[4.4.4]-propellene with a silicon-silicon bridgehead bond [dSi-Si = 2.2947(19) Å, av]. Compound 2 is the first dithiolene-based unsaturated propellane. X-ray structural analysis confirms that 2 exists in P- and M-helical forms in the solid state. Density functional theory (DFT) computations reveal that the helical chirality of 2 originates from steric interactions between the bulky substituents of the dithiolene ligands.