The reaction mixture immediately turned dark green and was allowed to warm to room temperature. After 16 h, the volatiles were removed in vacuo and the product was redissolved in hexane (2 mL). C{ 1 H} or Si DEPT NMR spectra of 4-Yb that could be assigned to the complex due to paramagnetic broadening, and we could not fully interpret the 1 H NMR spectrum of this complex, though a broad a beam profile was applied. The structures were solved variously using SHELXT (2-Tm, 2-Yb, 4-Sm, 4-Tm) or by direct and heavy atom methods using SHELXS (4-Yb). The datasets were refined by full-matrix least-squares on all unique F 2 values, with anisotropic displacement parameters for all non-hydrogen atoms, and with constrained riding hydrogen geometries; Uiso(H) was set at 1.2 (1.5 for methyl groups) times Ueq of the parent atom. Significantly disordered solvent was observed in most structures (2-Tm, 2-Sm, 4-Tm, 4-Yb), which could not be modelled sensibly, and in some cases the solvent identity was unclear. Contributions from disordered solvent were removed using SQUEEZE in Platon 62 (2-Tm, 4-Sm) or OLEX2 63 (4-Tm, 4-Yb). This corresponded to one molecule of hexane per complex of 2-Tm, one molecule of DCM per complex of 4-Sm and half a molecule of DCM or benzene per complex of 4-Tm or 4-Yb. The largest features in final difference syntheses were close to heavy atoms and were of no chemical significance. CrysAlisPro 58 was used for control and integration, and SHELX was employed through OLEX2 for structure solution and refinement. ORTEP-3 and POV-Ray were employed for molecular graphics.