An Actinide Metallacyclopropene Complex: Synthesis, Structure, Reactivity, and Computational Studies

The
synthesis, structure, and reactivity of an actinide metallacyclopropene
were comprehensively studied. The reduction of [η5-1,2,4-(Me3C)3C5H2]2ThCl2 (1) with potassium graphite
(KC8) in the presence of diphenylacetylene (PhCCPh)
yields the first stable actinide metallacyclopropene [η5-1,2,4-(Me3C)3C5H2]2Th­(η2-C2Ph2)
(2). The magnetic susceptibility data show that 2 is indeed a diamagnetic Th­(IV) complex, and density functional
theory (DFT) studies suggest that the 5f orbitals contribute to the
bonding of the metallacyclopropene Th(η2-CC)
moiety. Complex 2 shows no reactivity toward alkynes,
but it reacts with a variety of heterounsaturated molecules such as
aldehyde, ketone, carbodiimide, nitrile, organic azide, and diazoalkane
derivatives. DFT studies complement the experimental observations
and provide additional insights. Furthermore, a comparison between
Th and group 4 metals reveals that Th4+ shows unique reactivity
patterns.