Unfortunately, fluorobenzene solutions of the hydrocarbon-insoluble components layered with n-hexane consistently gave crystals of 1-Ln contaminated with [HNEt3][Al{OC(CF3)3}4], even when the ammonium salt was used sub-stoichiometrically. As such, pure samples of 1-Ln were prepared in 73-79% crystalline yields by a hydride abstraction strategy via the reaction of isolated 4-Ln with 0.9 eq. of in fluorobenzene at 20 °C for 18 h, followed by slow diffusion of n-hexane into the resulting solutions. Treating a mixture of 1-Y and [HNEt3][Al{OC(CF3)3}4] with excess [K{N(Si i Pr3)2}] gives 1 H, C{ 1 H} DEPTQ, Si{ 1 H} DEPT90, and each contain a single resonance (δB/ppm = -18.1, 2-Dy; -9.9, 3-Dy; -14.1, 4-Dy). Additionally, the solution magnetic susceptibilities of these complexes were determined at 298 K by the Evans method; 36 all values obtained (range χT = 12.5-14.2 cm 3 K mol -1 ) are in line with that expected for a Dy(III) free ion (χT = 14.17 cm 3 K mol -1 ). The species assigned as the cyclometalate 5-Y exhibits three signals in the Si{ 1 H} DEPT90 NMR spectrum at -3.2, -5.8 and -7.6 ppm. Three magnetically inequivalent silyl groups are also seen in the corresponding 1 H and 13 C{ 1 H} DEPTQ NMR spectra; the latter spectrum contains a doublet resonance at δC = 55.3 ppm; 1 JYC = 47.4 Hz with the correct phase for a methylene group, which was assigned to the Ybound carbon atom. Due to the presence of multiple coincident resonances in 1 H- C HSQC and 1 H- C HMBC NMR spectra we were unable to assign the associated 1 H resonances, precluding a definitive assignment of molecular connectivity. The resonances assigned to 5-Y in the 1 H, The ATR-IR spectra of each Dy/Y pair in 1-Ln, 2-Ln, 3-Ln and 4-Ln overlap with each other, and show a number of red-shifted C-H stretching bands that are diagnostic of some methine and methyl groups being in close proximity to the Ln centers (see Supporting Information Figures ). These ). For 1-Ln these features extend down to 2560 cm -1 , with the lowest energy modes computationally assigned to the methine C-H group that is closest to the Ln center; the corresponding resonance for 3-Ln is at 2745 cm -1 , and for 4-Ln there are two bands at 2756 cm -1 and 2729 cm -1 . Characteristic borohydride vibrations were also observed for 2-Ln, 3-Ln and 4-Ln; the apical B-H stretch of the terminal borohydrides correspond to sharp features at 2486 cm -1 , 2519 cm -1 , and 2495 cm -1 for 2-Ln, 3-Ln and 4-Ln respectively, whilst the stretching modes of the B-H bonds that are proximal to the metal give broad, convoluted bands between 2360 and 2060 cm -1 for all complexes. The [Dy{N(Si i Pr3)2}2] + cation exhibits a bent geometry, with a N-Dy-N angle that deviates significantly from linearity (128.7(2)°), with the NSi2 fragments in a staggered conformation (twist angle: 63.12(6)°), and mean Dy-N distances of 2.206(7) Å. The structure of this cation is similar to the previously reported Sm, Tm and Yb congeners, with deviations in metrical parameters expected on the basis of variation of Ln(III) cation size and Lewis acidity. In common with the previously reported heavy the electron density of the Si-C/C-H bonds of the silyl groups, as previously described for Sm, Tm and Yb congeners. Powder XRD was performed on a sample of microcrystalline 1-Dy (see Supporting Information Figure and Table ), confirming that the single crystal structure obtained is representative of the bulk crystalline material used for magnetic characterization.