Nucleophilic Aromatic Substitution at Benzene with Powerful Strontium Hydride and Alkyl Complexes

Key to the isolation of the first alkyl strontium complex was the synthesis of a strontium hydride complex that is stable towards ligand exchange reactions. This goal was achieved by using the super bulky beta-diketiminate ligand (BDI)-B-DIPeP (CH[C(Me)N-DIPeP](2), DIPeP = 2,6-diisopentylphenyl). Reaction of (BDI)-B-DIPeP-H with Sr[N(SiMe3)(2)](2) gave ((BDI)-B-DIPeP)SrN(SiMe3)(3) which was converted with PhSiH3 into [((BDI)-B-DIPeP)SrH2]. Dissolved in C6D6, the strontium hydride complex is stable up to 70 degrees C At 60 degrees C, H-D isotope exchange gave full conversion into ([(BDI)-B-DIPeP)SrD](2) and C6D5H. Since H-D exchange with D-2 is facile, the strontium hydride complex served as a catalyst for the deuteration of C6H6 by D-2. Reaction of [( (BDI)-B-DIPeP)SrH](2) with ethylene gave [( (BDI)-B-DIPeP)SrEt](2). The high reactivity of this alkyl strontium complex is demonstrated by facile ethylene polymerization and nucleophilic aromatic substitution with C6D6, giving alkylated aromatic products and [((BDI)-B-DIPeP)SrD](2).