Insertion Reaction of Phenyl Isocyanate into the Ln−C σ-Bond of Organolanthanide Complexes: Synthesis, Characterization, and Crystal Structures of {(C₅H₄CH₃)₂Ln[μ-η¹:η³-OC(R)NPh]}₂ (Ln = Sm, Dy, Er, Ho; R = <i>n</i>-butyl, α-naphthyl)

Abstract

Cp‘2LnR(THF) (Cp‘ = C5H4CH3) reacted with phenyl isocyanate to form the PhNCO insertion products [Cp‘2Ln(OC(R)NPh)]2 [R = n-butyl, Ln = Sm (1), Dy (2), Er (3); R = α-naphthyl, Ln = Dy (4)]. It was found that an excess of PhNCO did not affect the nature of the final complexes, a single insertion only being observed and excess PhNCO forming a cyclotrimer (5). The reaction of Cp‘HoCl2(THF)3 with BunLi and subsequently with 2 equiv of PhNCO in THF gave Ho[OC(Bun)NPh)]3 (6) and [Cp‘2Ho(OC(Bun)NPh)]2 (7), which can be rationalized by the rearrangement reaction of the di-insertion product Cp‘Ho[OC(Bun)NPh]2(THF)x. The structures of 1, 4·THF, 5·THF and 7 were determined by X-ray diffraction, revealing an unusual bonding mode of the amido groups arising from the insertion of PhNCO into the Ln−C σ-bonds and that the OCN fragment of the OC(R)NPh ligand acts as both a bridging and side-on chelating group.