Reactivityof Bestmann’s Ylide, Ph3PCOO, with the Actinides:Observation of An–C Bond Insertionor κ-O Coordination

Reaction of 2 equiv of Bestmann’s ylide, Ph3PCCO, with the Th(IV) metallacycle, [Th{N(R)(SiMe2CH2)}(NR2)2] (R = SiMe3), results in formation of [Th{N(R)(SiMe2CHC(C(H)PPh3)O}(NR2)2(OCCPPh3)] (1). The first equivalent of phosphoranylideneketene inserts into the Th–C bond, which is accompanied by a 1,3-H shift to form an η3-oxy-allyl fragment. The second equivalent of Ph3PCCO coordinates to the metal center in a κ-O fashion. Reaction of [AnCl(NR2)3] (An = U, Th) with 1 equiv of Ph3PCCO results in the formation of [AnCl(NR2)3(OCCPPh3)] (An = U, 2; Th, 3) in good yields. In both cases, the phosphoranylideneketene coordinates to the metal center in a κ-O fashion. Complexes 1, 2, and 3 were characterized by NMR and IR spectroscopies and X-ray crystallography. They represent the first reported actinide phosphoranylideneketene complexes.