AbstractAlthough the nucleophilic alkylation of aromatics has recently been achieved with a variety of potent main group reagents, all of this reactivity is limited to a stoichiometric regime. We now report that the ytterbium(II) hydride, [BDI^DippYbH]₂ (BDI^Dipp = CH[C(CH₃)NDipp]₂, Dipp = 2,6-diisopropylphenyl), reacts with ethene and propene to provide the ytterbium(II) n-alkyls, [BDI^DippYbR]₂ (R = Et or Pr), both of which alkylate benzene at room temperature. Density functional theory (DFT) calculations indicate that this latter process operates through the nucleophilic (S_N2) displacement of hydride, while the resultant regeneration of [BDI^DippYbH]₂ facilitates further reaction with ethene or propene and enables the direct catalytic (anti-Markovnikov) hydroarylation of both alkenes with a benzene C-H bond.