Complexes 1-Ln were prepared by adapting literature procedures for the salt metathesis reactions of [LnI3(THF)x] (Ln = La, Ce, Pr, x = 4; Ln = Nd, Sm, x = 3.5) with 3 eq. KP(SiMe3)2 in diethyl ether (Scheme 1). We were not able to isolate significant quantities of 1-Ln by following the previously reported conditions for the synthesis of 1-Nd using THF as the reaction solvent. Upon noting that reaction mixtures tended to darken over time at room temperature we hypothesized that decomposition pathways involving THF (e.g. ring opening) were occurring. We therefore changed the reaction solvent to diethyl ether and maintained reaction mixtures at -78 ℃ for 1 hour before briefly allowing to return to room temperature with stirring; all volatiles were then removed under vacuum and products were extracted into hexane. Filtration and concentration of hexane extracts and storage at -30 °C overnight reproducibly gave 1-Ln in low crystalline yields (14-50%) under these optimized conditions. Overlapping absorption features were observed in the ATR-IR spectra of microcrystalline 1-Ln (see Supporting Information Figures ), indicating that they exhibit similar bulk structural features. Elemental analyses performed on 1-Ln reproducibly gave carbon values that were lower than those predicted. This observation was previously made for 1-Nd even when combustion agents were added, and was attributed to carbide formation. Whilst this could be interpreted as an intrinsic feature for the 1-Ln family, we note that low carbon values were also obtained for [M{Si(SiMe3)3}3(THF)2], and this can be a general feature depending on experimental set-up. However, all other analytical data collected for 1-Ln are in accord with their bulk purities (see below).