Contrasting Reactions of Carbodiimides with Divalent Lanthanoid Species

Reactions of lanthanoid species with carbodiimides (RN ═ C ═ NR') show considerable variety. Thus, treatment of the divalent 2,6-di-tert-butyl-4-ethylphenolatosamarium complex, [Sm(OAr^Et)₂(thf)₃]·PhMe with N,N'-diisopropylcarbodiimide (iPrNCNiPr) resulted in the formation of the oxalamidinatosamarium(III) complex [(OArEt)₂Sm(μ-C₂N₄iPr₄)Sm(OAr^Et)₂]·2PhMe (1). In contrast, the use of the bulkier N,N'-dicyclohexylcarbodiimide (CyNCNCy) led to the formation of a formamidinatosamarium(III) complex [Sm(OAr^Et)₂(CyNC(H)NCy)(thf)₂]⋅2thf (2). Reactions between rare earth metals (RE = Yb, Eu) with one molar equivalent of bis(phenylethynyl)mercury (Hg(PhCC)₂) and two molar equivalents of N,N'-dicyclohexylcarbodiimide (CyNCNCy) in tetrahydrofuran (thf) at room temperature yielded lanthanoid C-phenylethynylamidinate complexes, trivalent [Yb^III{CyNC(C≡CPh)NCy}₃]·2thf (3) and divalent [Eu{CyNC(C≡CPh)NCy}₂(thf)₂] (4). [Sm(OAr^Et)₂(thf)₃].PhMe was obtained from SmI₂(thf)₂ and the in situ generated potassium aryl oxide and is a five-coordinate monomer with a stereochemistry between trigonal bipyramidal and square pyramidal.