Syntheses and structures of lithiated sulfones Li[CR(R′)SO2Ph] – C versus O bound lithium. [{Li{CH(Me)SO2Ph}(thf)}∞] – The structure of a C-bound derivative

Sulfones RCH(R′)SO2Ph were reacted with n-BuLi in thf/n-hexane (R/R′ = H/Me, Me/Et, H/CH2Ph) and toluene/n-hexane (R/R′ = Me/Ph) yielding under deprotonation Li[CR(R′)SO2Ph] which reacted with Me3SiCl and n-Bu3SnCl forming the requisite trimethylsilyl and tri(n  -butyl)tin substituted derivatives R3″E-C(R)R′SO2Ph(R3″E=Me3Si,n-Bu3Sn). Performing the reactions of RCH(R′)SO2Ph with n-BuLi in n-hexane (instead of thf/n-hexane) and toluene/n-hexane, respectively, resulted in the precipitation of the organo lithium compounds Li[CR(R′)SO2Ph] (1–4) which were isolated as strongly moisture-sensitive yellow powders in essentially quantitative yields. Their identities were confirmed by 1H and 13C NMR spectroscopic measurements in thf-d8. Solutions of each 1, 3, and 4 in thf/n-hexane and thf/n-pentane afforded crystals of each [{Li{CH(Me)SO2Ph}(thf)}∞] (1a), [{Li{CH(CH2Ph)SO2Ph}(thf)}∞] (3a), and [{Li{CMe(Ph)SO2Ph}(thf)2}2] (4a), respectively, whose structures were determined by single-crystal X-ray crystallography. The compounds 1a and 3a crystallize in 1D polymeric ladder-like structures. The strands of 1a are built-up by eight-membered Li2C2S2O2 rings having direct Li–C bonding interactions (Li–C 2.215(5) Å). The donor set of Li is completed by three oxygen atoms, one from the thf ligand and two from SO2 groups of neighboring Li{CH(Me)SO2Ph}(thf) entities. The strands of 3a are built-up of alternating Li2S2O4 eight- and Li2O2 four-membered rings. Each lithium atom is coordinated to three oxygen atoms, two from O2S(Ph)CHCH2Ph groups and one from thf oxygen atom. There is no Li–C bonding. Compound 4a crystallizes in dimers consisting of eight-membered Li2S2O4 rings in which the two lithium atoms are bridged by two O2S(Ph)CHMePh groups. The coordination sphere of lithium is completed by two oxygen atoms of the thf ligands.

Graphical abstractThe synthesis of solvate-free lithiated sulfones Li[CR(R′)SO2Ph] is described. Crystallization from thf/n-hexane or thf/n-pentane resulted in the formation of their tetrahydrofuran adducts in well-shaped crystals of [{Li{CH(Me)SO2Ph}(thf)}∞] (1a), [{Li{CH(CH2Ph)SO2Ph}(thf)}∞] (3a), and [{Li{CMe(Ph)SO2Ph}(thf)2}2] (4a), whose structures were determined by single-crystal X-ray crystallography. In the solid state, 1a and 3a exhibited 1D polymeric structures that are unprecedented so far. Compound 1a is one of the rare example of lithiated sulfones having a Li–C bond whereas in 3a and 4a the lithium adopts the usual O coordination.Figure optionsDownload full-size imageDownload as PowerPoint slide