Insertion of a Carbodiimide into the Ln−N σ-Bond of Organolanthanide Complexes. Isomerization and Rearrangement of Organolanthanides Containing Guanidinate Ligands

The reaction of (C5H5)YCl2(THF)3 with LiNiPr2 and subsequently with 2 equiv of N,N‘-diisopropylcarbodiimide (iPrNCNiPr) in THF gave the organoyttrium guanidinates
Y[iPrNC(NiPr2)NiPr]3 (1) and (C5H5)2Y[iPrNC(NiPr2)NiPr] (2), which may be rationalized by
the rearrangement reaction of the diinsertion product (C5H5)Y[iPrNC(NiPr2)NiPr]2. Treatment
of iPrNCNiPr with lanthanocene primary amides [(C5H5)2LnNHR]2 (R = tBu, Ln = Yb,
Er, Dy, Y; R = Ph, Ln = Yb) gave the unexpected products (C5H5)2Yb[RNC(NHiPr)NiPr] (R
= tBu, Ln = Yb (3), Er (4), Dy (5), Y(6); R = Ph, Ln = Yb (7)), indicating that a novel
isomerization reaction involving a 1,3-hydrogen shift takes place along with the insertion of
carbodiimide into the Ln−N σ-bond, which provides an efficient synthesis of organolanthanide
complexes with asymmetrical guanidinate ligands. All these complexes were characterized
by elemental analysis and spectroscopic properties. The structures of complexes 1−5 and 7
were also determined by X-ray diffraction analysis.