Reactivity of Organolanthanide and Organolithium Complexes Containing the Guanidinate Ligands toward Isocyanate or Carbodiimide: Synthesis and Crystal Structures

The direct reactions of (C5H5)2LnCl with LiNC(NMe2)2 proceeded at room temperature in THF under pure nitrogen
to yield the lanthanocene guanidinate complexes [(C5H5)2Ln(μ-η1:η2-NC(NMe2)2)]2 (Ln = Gd (1), Er (2)). Treatment
of phenyl isocyanate with complexes 1 and 2 results in monoinsertion of phenyl isocyanate into the Ln−N(μ-Gua)
bond to yield the corresponding insertion products [(C5H5)2Ln(μ-η1:η2-OC(NC(NMe2)2)NPh)]2 (Ln = Gd (3), Er
(4)), presenting the first example of unsaturated organic small molecule insertion into the metal−guanidinate ligand
bond. Further investigations indicate that N,N‘-diisopropylcarbodiimide does not react with complexes 1 and 2
under the same conditions; however, it readily inserts into the lithium−guanidinate ligand bond of LiNC(NMe2)2.
As a synthon of the insertion product Li[(iPrN)2C(NC(NMe2)2)], its reaction with (C5H5)2LnCl gives the novel
organolanthanide complexes containing the guanidinoacetamidinate ligand, (C5H5)2Ln[(iPrN)2C(NC(NMe2)2)] (Ln
= Yb (5), Er (6), Dy (7)). All complexes were characterized by elemental analysis and spectroscopic properties.
The structures of complexes 1, 3, 5 and 7 were determined through X-ray single-crystal diffraction analysis.