Lanthanoid-Carbodiimide Chemistry

Peter Courtney Junk, James Cook University, Townsville, Australia, and colleageus have investigated the reactions of unsaturated carbodiimide substrates (RN=C=NR’) with Ln^II aryloxides, providing a potential route to novel amidinatolanthanoid complexes. Additionally, they investigated how a carbodiimide reacts with organolanthanoid alkynyl complexes formed through redox transmetallation to evaluate its insertion into Ln–C sigma bonds.

Samarium

The team reaced the divalent samarium complex [Sm(OArEt)₂(thf)₃] with N,N’-diisopropylcarbodiimide (iPrNCNiPr) to produce the oxalamidinatosamarium(III) complex [(OArEt)₂Sm(μ-C₂N₄iPr₄)Sm(OArEt)₂]·2PhMe (1). Using the bulkier N,N’-dicyclohexylcarbodiimide (CyNCNCy) led to the mononuclear formamidinatosamarium(III) complex [Sm(OArEt)₂(CyNC(H)NCy)(thf)₂]×2thf (2).

Complex (1) crystallizes in the triclinic space group P-1. Each Sm atom is bound to one side of the tetraisopropyloxalamidinate ((iPr)₂N₂C-CN₂(iPr)₂²⁻) ligand, which functions as a bridging tetradentate ligand by chelating both Sm atoms through four nitrogen atoms. Complex (2) crystallizes in the monoclinic P2₁/c space group. The Sm atom is six-coordinate and the geometry around the Sm center is near pseudo square pyramidal.

Ytterbium and Europium

The team found that reactions between the rare earth metals ytterbium and europium 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).

The six coordinated complex (3) crystallizes in the triclinic P-1 space group, adopting a pseudotrigonal planar geometry if the phenylethynyl-substituted amidinate ligands are considered point donors located at the central carbon atoms. Complex (4) crystallizes in the monoclinic system, space group P2₁/c. In the monomeric complex, the Eu atom is six-coordinate, with four N atoms from chelating amidinates fragments.