Activation of Bis(guanidinate)lanthanide Alkyl and Aryl Complexes on Elemental Sulfur: Synthesis and Characterization of Bis(guanidinate)lanthanide Thiolates and Disulfides

The treatment of [(Me3Si)2NC(NCy)2]2Ln(μ-Cl)2Li(THF)2 with 1 equiv of BnK (Bn = benzyl) in toluene affords [(Me3Si)2NC(NCy)2]2LnBn [Ln = Er (1-Er), Y (1-Y)] in good yields. Similarly, [(Me3Si)2NC(NCy)2]2LntBu [Ln = Er (2-Er), Yb (2-Yb)] are obtained in satisfactory yields by the reaction of [(Me3Si)2NC(NCy)2]2Ln(μ-Cl)2Li(THF)2 with tBuLi in hexane. 1 reacts with 1/8 equiv of S8 in toluene to form the sulfur insertion products {[(Me3Si)2NC(NCy)2]2Ln(μ-SBn)}2 [Ln = Er (3-Er), Y (3-Y)], while the reaction of 2 with elemental sulfur under the same conditions affords the oxidation products {[(Me3Si)2NC(NCy)2]2Ln}2(μ-η2:η2-S2) [Ln = Er (4-Er), Yb (4-Yb)] regardless of the equivalency of S8 employed. Disulfide complexes 4 can also be obtained by the reaction of 3 with 1/4 equiv of S8. Furthermore, the treatment of [(Me3Si)2NC(NCy)2]2Ln(μ-Cl)2Li(THF)2 with 1 equiv of nBuLi in hexane, followed by reaction with 1/8 equiv of S8, affords the dinuclear thiolate complexes {[(Me3Si)2NC(NCy)2]2Ln(μ-SnBu)}2 [Ln = Y (5-Y), Er (5-Er)] in good yields. However, under the same conditions, [(Me3Si)2NC(NCy)2]2Yb(μ-Cl)2Li(THF)2 reacts with nBuLi and S8 to give {[(Me3Si)2NC(NCy)2]2Yb}2(μ-η2:η2-S2) (4-Yb) as the main metal-containing product. [(Me3Si)2NC(NCy)2]2LnPh (generated in situ from [(Me3Si)2NC(NCy)2]2Ln(μ-Cl)2Li(THF)2 and PhLi) also undergoes sulfur insertion, affording {[(Me3Si)2NC(NCy)2]2Ln(μ-SPh)}2 [Ln = Er (6-Er), Yb (6-Yb)] in good yields. All of the complexes were characterized by spectroscopic and elemental analyses. The structures of all of these compounds, except 3-Y, are also determined by single-crystal X-ray diffraction analysis. Surprisingly, 3, 5, and 6 bear the same space group and very similar cell parameters, despite the different thiolate ligands.