Non‐Classical Early Lanthanide(II) Tris(di‐tert‐butylcyclopentadienyl) Complexes**

Abstract

AbstractWe report the synthesis of a series of temperature‐sensitive non‐classical early Ln(II) (Ln=lanthanide) complexes, [K(2.2.2‐cryptand)][Ln(Cptt)3] (Cptt=C5H3tBu2‐1,3; 1‐Ln; Ln=La−Nd). Complexes 1‐Ln were typically prepared using Schlenk line techniques rather than more common glove box protocols, by the reduction of the parent Ln(III) complexes [Ln(Cptt)3] (2‐Ln) with KC8 in THF in the presence of 2.2.2‐cryptand at −30 °C. The majority of the 2‐Ln series have been reported previously by the salt metathesis reactions of 3 eq. KCptt with parent LnCl3, and these methods were adapted here to afford 2‐Pr. Complexes 1‐Ln and 2‐Pr were characterized by single crystal XRD, elemental analysis, ATR‐IR and UV‐Vis‐NIR spectroscopy; 1‐La and 2‐Pr were additionally characterized by c.w. EPR spectroscopy, and variable temperature magnetic susceptibility measurements were performed on 2‐Pr. During attempts to synthesize 2‐Nd and 2‐Sm we also obtained small crops of crystals of [Nd(Cptt)2(μ‐I)]2 (3) and [Sm(Cptt)2(μ‐Cl)]2 ⋅ C7H8 (4 ⋅ C7H8), respectively; these complexes were also structurally authenticated, and magnetic data was collected for 4 ⋅ C7H8. The combination of data obtained indicate that the Ln(II) centers in 1‐Ln adopt 4fn5d1 electron configurations, in common with other literature examples of [Ln(CpR)3]− anions (CpR=substituted cyclopentadienyl) for these metals.