Neutral and Cationic Silicon Species Containing Aryl-OCO- or Aryl-SCS-Type Pincer Ligands: Synthesis, Structure, Bonding, and Comparison with Aryl-NCN Systems

The reaction of dichloro(methyl)silane, dichloro(phenyl)silane or dichloro(dimethyl)silane with one equivalent of the lithiated aryl pincer ligands [2,6-(DoCH(2))(2)H3C6]Li leads to the chlorosilanes [2,6-(DoCH(2))(2)H3C6]SiRR'Cl 1-6, respectively, as thermolabile oily compounds. Treatment of 1-6 with trimethylsilyl triflate leads to the crystalline ionic silicon triflates [2,6-(DoCH(2))(2)H3C6SiRR'](+)center dot X- 7-12, respectively [(X = OSO2CF3), 1, 7: Do = OMe, 2, 8: Do = SMe, 1, 2, 7, 8: R = Me, R' = H; 3, 9: Do = OMe, 4, 10: Do = SMe, 3, 4, 9, 10: R = Ph, R' = H; 5, 11: Do = OMe, 6, 12 = SMe, 5, 6, 11, 12: R R' = Me]. The compounds 1-12 are characterized by NMR spectroscopy, by conductivity measurements, and by X-ray crystallography (8-12). The NMR parameters delta Si, (1)J(SiH) and delta H(SiH) and some structural data are compared with those of known compounds containing one NCN-pincer aryl ligand or two aryl substituents of the type [2-(DoCH(2))(2)H4C6]. Differences in bonding depending on the type of the donor Do (NMe2, OMe, SMe) are discussed.