Methane and Benzene Activation via Transient (t-Bu3SiNH)2Zr=NSi-t-BU3

摘要

Over the past decade, the activation of carbon-hydrogen bonds by transition-metal complexes has undergone intense investigation. Alkane dehydrogenations, discrete RH oxidative additions, free-radical processes, and Sigma-bond metatheses comprise most of the reactivity investigated. Reactions of alkanes with multiply bonded functionalities are rare yet constitute an important class of transformations related to the partial oxidation or functionalization of unactivated C-H bonds. During the course of assessing the utility of t-Bu3SiNH- as an ancillary ligand related to t-Bu3SiO- (Silox), a mode of intermolecular C-H activation involving addition across a transient zirconium imide was discovered. Treatment of Zirconium tetrachloride with 3 equiv of t-Bi3SiNHLi, prepared from n-BuLi and t-Bu3SiNH2, resulted in the formation of (t-Bu3SiNH)3ZrCl (1, eq 1) in 88% yield. Alkylation of 1 with appropriate Grignard reagents yielded white crystals of the methyl, phenyl, and cyclohexyl (Cy) derivatives, (t-Bu3SiNH)3ZrR ( R = Me. Reprints. (aw)