Synthesis and Characterization of the Monomeric Vicinal Dianion Li2(THF)3[ArNC(SiMe3)2] and the Aluminum and Lithium Derivatives of the Amido Ligand [ArNCH(SiMe3)2]−
摘要:
Reaction of the imine ArNC(SiMe3)(2) (1; Ar = 2,6-iPr(2)C(6)H(3)) with LiAlH4 in THF resulted in the formation of the dimeric hydroaluminate [(THF)(2)LiH3AlL](2) (2; L = [ArNCH(SiMe3)(2)](-)). 2 reacted with CH3I to give the monomeric aluminum dihydride LAlH2(THF) (3), which can be converted to the diiodide LAlI2(THF) (4) upon treatment with 2 equiv of Me3SiI. The quasi two-coordinate lithium amide Li(OEt2)L (8) with an intramolecular CH-Li interaction was obtained by the deprotonation of the corresponding amine LH (5) generated from hydrolysis of 2. Reduction of 1 with lithium in THF resulted in the first structurally characterized monomeric C-N vicinal dianion, Li-2(THF)(3)[ArNC(SiMe3)(2)] (6), and the monomeric lithium amide Li(THF)(2)L (7).
Palladium-catalyzed insertion of isocyanides into the silicon-silicon linkages of oligosilanes
摘要:
Full details of a study on the reactions of oligosilanes with isocyanides promoted by a palladium catalyst are described. Heating a mixture of oligosilanes and excess 2,6-disubstituted aryl isocyanide in the presence of palladium(II) acetate led to the complete insertion of isocyanide into all silicon-silicon linkages, giving oligo(silylimine) derivatives. The oligo(silylimine)s have been isolated and characterized so far in the complete insertion reaction with oligosilanes up to a hexasilane. Use of the limiting amount of isocyanide permitted insertion of isocyanide into predominantly the terminal silicon-silicon linkages. The mode of the insertion reaction depends on the substituent at the silicon, e.g., tetrasilanes with phenyl groups on the internal silicon atoms favorably underwent the insertion reaction at the terminal silicon-silicon linkages, resulting in the partial insertion. The bulkiness of the ortho substituents on the aromatic isocyanide was also found to have much influence on the insertion; hence, 2,6-diisopropylphenyl isocyanide favored the partial insertion. New skeletal rearrangement of oligosilanes took place in a palladium-catalyzed reaction of substituted aryl isocyanide with tetra- and hexasilanes, forming 3,3-bis(silyl)-l-aza-2, 4-disilacyclobutane derivatives. The rearrangement, which is unique and intriguing in that the product is properly reconstituted from four fragments of the tetrasilane and two fragments of the isocyanide, was promoted in the copresence of a tert-alkyl isocyanide.