Si–H addition followed by C–H bond activation induced by a terminal thorium imido metallocene: a combined experimental and computational study

Abstract

The Si–H bond addition to a terminal actinide imido complex was comprehensively studied. The base-free thorium imido [η⁵-1,2,4-(Me₃C)₃C₅H₂]₂ThN(p-tolyl) (1) activates Si–H bonds in PhSiH₃ or Ph₂SiH₂ to give the thorium amido hydrido metallocenes [η⁵-1,2,4-(Me₃C)₃C₅H₂]₂Th(H)[N(p-tolyl)SiH₂Ph] (2) and [η⁵-1,2,4-(Me₃C)₃C₅H₂]₂Th(H)[N(p-tolyl)SiHPh₂] (3), respectively. Complex 2 readily inserts unsaturated molecules into the Th–H bond, whereas complex 3 reversibly activates an intramolecular aromatic C–H bond to yield [η⁵-1,2,4-(Me₃C)₃C₅H₂]₂Th[η²-N,C-{N(p-MeC₆H₃)(SiHPh₂)}] (4) and H₂. The experimental results have been complemented by density functional theory (DFT) studies and provide a detailed understanding of the observed reactivity. In addition, a comparison between Th and early transition metals reveals that the Th⁴⁺ behaves more like an actinide than a transition metal.