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

The Si-H bond addition to a terminal actinide imido complex was comprehensively studied. The base-free thorium imido [eta(5)-1,2,4-(Me3C)(3)C5H2](2)Th = N(p-tolyl) (1) activates Si-H bonds in PhSiH3 or Ph2SiH2 to give the thorium amido hydrido metallocenes [eta(5)-1,2,4(Me3C)(3)C5H2](2)Th(H)[N(p-tolyl) SiH2Ph] (2) and [eta(5)-1,2,4-(Me3C)(3)C5H2] Th-2(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 [eta(5)-1,2,4-(Me3C) 3C5H2](2)Th[eta(2)-N,C-{N(p-MeC6H3)(SiHPh2)}] (4) and H-2. 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.