The ketimide ligand is not just an inert spectator: Heteroallene insertion reactivity of an actinide-ketimide linkage in a thorium carbene amide ketimide complex

Abstract

The ketimide anion R2C-N- is an important class of chemically robust ligand that binds strongly to metal ions and is considered ideal for supporting reactive metal fragments due to its inert spectator nature; this contrasts with R2N- amides that exhibit a wide range of reactivities. Here, we report the synthesis and characterization of a rare example of an actinide ketimide complex [Th(BIPMTMS){N(SiMe 3)2}(N-CPh2)] [2, BIPMTMS=C(PPh 2NSiMe3)2]. Complex 2 contains Th-C carbene, Th-Namide and Th-Nketimide linkages, thereby presenting the opportunity to probe the preferential reactivity of these linkages. Importantly, reactivity studies of 2 with unsaturated substrates shows that insertion reactions occur preferentially at the Th-N ketimide bond rather than at the Th-Ccarbene or Th-N amide bonds. This overturns the established view that metal-ketimide linkages are purely inert spectators. Inert no more: The thorium carbene amide ketimide complex [Th(BIPMTMS){N(SiMe3)2}(N- CPh2)] [BIPMTMS=C(PPh2NSiMe3) 2] features Th-C, Th-Namide, and Th-Nketimide bonds in one molecule. Reactivity studies show that reactions preferentially involve the traditionally inert Th-Nketimide linkage rather than the usually reactive Th-C or Th-Namide bonds, and overturn the established view of ketimides as purely inert spectator ligands. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.