Complexes 1-Ln (Ln = La, Ce, Nd, Sm) were prepared from the parent LnCl3 and three equivalents of KCp tt (Scheme 1) by modification of the reported syntheses of 1-Sm using SmI3 and KCp tt , and 1-Ce from Ce(OTf)3 and LiCp tt . The crystalline yields for 1-La, 1-Ce, 1-Nd and 1-Sm were 41%, 54%, 34% and 52%, respectively. NMR spectroscopy was used to analyse C6D6 solutions of 1-Ln (Supporting Information Figures ). 1 H NMR spectra were fully assigned for all 1-Ln; in each case three signals were observed in a ratio of 54:6:3 that correspond to the t Bu groups and the two unique environments of the Cp tt ring protons, respectively. The paramagnetism of 1-Ce, 1-Nd and 1-Sm precluded assignment of their C{ 1 H} NMR spectra, however, for diamagnetic 1-La this could be interpreted, with the two t Bu group resonances seen at 32.77 and 33.75 ppm and the three Cp tt ring carbon environments found at 110.57 (CH-Cp), 110.69 (CH-Cp) and 143.45 (C-Cp) ppm. Although NMR spectroscopy showed few protic impurities, elemental analysis results for 1-Ln consistently gave low carbon values; this was previously seen for [An(Cp tt )3], and is ascribed to carbide formation leading to partial combustion, a common issue with these experiments. In the case of 1-Sm elemental analysis results were not in accord with expected values, but ATR-IR spectra of all complexes were essentially superimposable, giving confidence to their bulk purities (Supporting Information Figures ).