Rare earth metalbis(trimethylsilyl)amido complexes bearing pyrrolyl-methylamide ligand. Synthesis, structure, and catalytic activity towards guanylation of amines

Abstract

The N-arylaminomethyl substituted pyrrolyl ligand 2-[(2,4,6-Me₃C₆H₂)NHCH₂](C₄H₃NH) (1) was synthesized by reduction of 2-[(2,4,6-Me₃C₆H₂)NCH](C₄H₃NH) using NaBH₄. Treatment of [(Me₃Si)₂N]₃Ln(μ-Cl)Li(THF)₃ with 1 equiv. of 1 in reflux toluene for 24 h, afforded the corresponding trivalent rare earth metal amides with formula {(μ-η⁵:η¹):η¹-2-[(2,4,6-Me₃C₆H₂)NCH₂]C₄H₃N]LnN(SiMe₃)₂}₂ (Ln = Y(2), Nd(3), Sm(4), Dy(5), Er(6)). All compounds were fully characterised by spectroscopic methods and elemental analyses. The structures of complexes 2, 4 and 6 were determined by single-crystal X-ray analyses. X-Ray analyses discovered that two rare-earth metal ions were bridged by dianion ligand with the pyrrolyl ring which coordinated to one rare earth metal in an η⁵ mode, the tethered nitrogen anion and nitrogen atom of the pyrrolyl ring coordinated to another rare earth metal in η¹ modes forming the centrosymmetric dinuclear structures. The rare earth metal complexes as catalysts for the guanylation of aromatic amines were studied. Results showed all rare earth metal complexes exhibited a high catalytic activity on the guanylation of aromatic amines.