Rare earth metal bis(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-Me(3)C(6)H(2))NHCH(2)](C(4)H(3)NH) (1) was synthesized by reduction of 2-[(2,4,6-Me(3)C(6)H(2))N=CH](C(4)H(3)NH) using NaBH(4). Treatment of [(Me(3)Si)(2)N](3)Ln(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-η(5):η(1)):η(1)-2-[(2,4,6-Me(3)C(6)H(2))NCH(2)]C(4)H(3)N]LnN(SiMe(3))(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 η(5) mode, the tethered nitrogen anion and nitrogen atom of the pyrrolyl ring coordinated to another rare earth metal in η(1) 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.