Thorium Mono- and Bis(imido) Complexes Made by Reprotonation of cyclo-Metalated Amides.

Molecules containing actinide-nitrogen multiple bonds are of current interest as simple models for new actinide nitride nuclear fuels, and for their potential for the catalytic activation of inert hydrocarbon C-H bonds. Complexes with up to three uranium-nitrogen double bonds are now being widely studied, yet those with one thorium-nitrogen double bond are rare, and those with two are unknown. A new, simple mono(imido) thorium complex and the first bis(imido) thorium complex, K[Th(═NAr)N″3] and K2[Th(═NAr)2N″2], are readily made from insertion reactions (Ar = aryl, N″ = N(SiMe3)2) into the Th-C bond of the cyclometalated thorium amides [ThN″2(N(SiMe3)(SiMe2CH2))] and K[ThN″(N(SiMe3)(SiMe2CH2))2]. X-ray and computational structural analyses show a "transition-metal-like" cis-bis(imido) geometry and polarized Th═N bonds with twice the Wiberg bond order of the formally single Th-N bond in the same molecule.