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.