Lanthanide(III)-bis(cyclopropylethinylamidinates): Synthesis, structure, and catalytic activity

•New lanthanide-bis(cyclopropylethinylamidinates) have been prepared.•The cerium and neodymium compounds are Cl-bridged dimers.•The complexes catalyze the addition of anilines to carbodiimides.

Reactions of anhydrous lanthanide trichlorides, LnCl3 (Ln = Ce, Nd, Ho), with 2 equiv. of lithium-cyclopropylethinylamidinates, Li[c-C3H5–CC–C(NR)2] (1a: R = iPr, 1b: R = cyclohexyl (Cy)), afforded a series of new lanthanide-bis(cyclopropylethinylamidinates). In the case of cerium and neodymium, the chloro-bridged dimers [{c-C3H5–CC–C(NR)2}2Ln(μ-Cl)(THF)]2 (2a: Ln = Ce, R = iPr; 2b: Ln = Ce, R = Cy; 2c: Ln = Nd, R = Cy) were isolated, whereas the smaller holmium afforded the “ate” complex [c-C3H5–CC–C(NCy)2]2Ho(μ-Cl)2Li(THF) (OEt2) (3). An initial study showed that these complexes effectively catalyze the addition of aniline derivatives to carbodiimides to give N-arylguanidines. The new complexes 2a–c and 3 as well as the N-arylguanidines o-C6H4(NH2)[-NC(NHiPr)2] (8) and p-C6H4Cl[-NC(NHiPr)2] (9) have been structurally characterized by X-ray diffraction.

Graphical abstractReactions of LnCl3 (Ln]Ce, Nd, Ho), with 2 equiv. of lithium-cyclopropylethinylamidinates, Li[c-C3H5–C C–C(NR)2] (R]iPr, Cy), afforded new lanthanide-bis(cyclopropylethinylamidinates). These complexes effectively catalyze the addition of aniline derivatives to carbodiimides to give N-arylguanidines. The new complexes as well as two N-arylguanidines have been structurally characterized by X-ray diffraction.Figure optionsDownload full-size imageDownload as PowerPoint slide