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 = n-butyl, α-naphthyl)

Cp'2LnR(THF) (Cp' = C5H4CH3) reacted with phenyl isocyanate to form the PhNCO insertion products [CP'(2)Ln(OC(R)NPh)](2) [R = n-butyl, Ln = Sm (1), Dy (2), Er (3); R = alpha -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 (BuLi)-Li-n and subsequently with 2 equiv of PhNCO in THF gave Ho[OC(Bu-n)NPh)](3) (6) and [CP'Ho-2(OC(Bu-n)NPh](2) (7), which can be rationalized by the rearrangement reaction of the di-insertion product Cp'Ho[OC(Bu-n)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 sigma -bonds and that the O-C-N fragment of the OC(R)NPh ligand acts as both a bridging and side-on chelating group.