Organolanthanide η1- and η5-pyrrolyl half-sandwich compounds: synthesis, structures, and magnetic properties

Abstract

The utilization of the di-pyrrolyl Schiff base ligand H₂L (H₂L = N-((1H-pyrrol-2-yl)methyl)-1-(1H-pyrrol-2-yl)methanimine) in organolanthanide chemistry is presented. The 1 : 2 reaction of [Ln(N(SiMe₃)₂)₃] (Ln = Dy, Ho, Er, and Gd) with H₂L in THF followed by recrystallization in THF/Tol or Tol generated complexes [Dy₂(HL)₂(L)₂(THF)₂]·2THF (1·2THF), [Ho₂(HL)₂(L)₂(THF)₂] (2), [Er₂(HL)₂(L)₂(THF)₂]·4Tol (3·4Tol), and [Gd₂(HL)₂(L)₂(THF)₂] (4). In the doubly deprotonated ligand [L]²⁻, one pyrrolyl ring adopts the η⁵ coordination mode, and the other pyrrolyl moiety behaves as an η¹ ligand. The deprotonated pyrrolyl scaffold of the [HL]⁻ ligand exhibits the η¹ coordination mode. Thus, the two metal centers both display a half-sandwich configuration. Studies of the dc magnetic susceptibility of 1-4 at variable temperatures showed that weak antiferromagnetic interactions exist in these compounds. The ac magnetic susceptibility measurements for 1 and 2 indicated that they did not display single-molecule magnetic (SMM) properties. The magnetic properties of 1 and 2 were further explained by DFT calculations.