New Chelating Ligands Based on S-Organosulfurdiimides: Synthesis and Single Crystal X-ray Structures of their Lithium Complexes

Three new diimidosulfinates, [(TMSCHS)-S-2((NBu)-Bu-t)(2)Li](2)(1),[2-PyCH2S((NBU)-B-t)(2)Li](2)(2), and [fPhCH(2)S((NBU)-B-t)(2)Li)(2)-THF] (3) (TMS = trimethylsilyl; Py = 2-pyridyl), have been synthesized by the reaction of functionalized (alpha-CH2-organolithium compounds with bis-tert-butylsulfurdiimide. These new organolithium chelates are characterized by NMR (H-1, (13)c, Li-7, and Si-29) spectroscopy and single-crystal X-ray diffraction analyses. Compounds 1 and 2 crystallize as dimers without donor molecules, whereas one of the lithium atoms in 3 is coordinated by a single THF molecule. The crystal structure of 1 shows significant intramolecular proximity between one methyl group of the trimethylsilyl (TMS) and one lithium atom, which could be described as an electrostatic Li center dot center dot center dot C interaction, The coordination sphere of each lithium atom in 2 is completed by donation from the nitrogen atom of the pyridyl ring; however, one of the lithium atoms in 3 is coordinated by a THF molecule. In addition, the first mixed sulfurdiimide species containing a diimidosulfinate and a diimidosulfite fragment, [{PhCHS((NBU)-B-t)(2)Li-2(THF)(2)} MeS((NBU)-B-t)(2)Li(THF)}] (4), was isolated by deprotonation of the (alpha-CH2 group in 3. The single-crystal X-ray structure of 4 revealed two different S-bound substituents coexisting in one dimer and two asymmetrically coordinated lithium atoms.