Lanthanides (Lns) have numerous applications due to their unique physicochemical properties. The textbook description of the electronic structure of Ln ions in the dominant 3+ oxidation state is that due to poor shielding the valence 4f orbitals are "core-like," and as a result chemical bonding involving Ln ions is predominantly ionic. In contrast to Ln, the early actinides (An) exhibit variable oxidation states and participation in metal-ligand multiple bonding, which indicates greater involvement of the 5f (and 6d) valence orbitals in bonding regimes. This is important because the extent of covalency in chemical bonding has direct impacts on electronic properties and chemical behavior of Ln and An, and such differences are exploited in, for example, separations technologies. The use of relatively soft donor ligands, such as substituted cyclopentadienyls (Cp R ), can introduce interesting bonding regimes, and [Ln/An(Cp)3] type complexes have long been used as a computational test-bed to investigate trends in the nature of f-element bonding. Since the majority of Ln and An 3+ ions are paramagnetic, electron paramagnetic resonance (EPR) spectroscopy should carry important information on metal-ligand bonding, particularly if resolution of ligand nuclear hyperfine interactions can be resolved. However, this is rarely the case in continuous wave (CW) EPR because of the intrinsically broad linewidths. This can in principle be addressed by pulsed EPR hyperfine methods. However, there are surprisingly few pulsed EPR studies on molecular Ln complexes, with the notable exception of those of the 8 S7/2 Gd 3+ ion, and even fewer for An complexes. Most Ln 3+ pulsed EPR studies have been performed on doped minerals or glasses, and have tended to focus on relaxation behaviour. In 2011 Denning and co-workers reported pulsed EPR measurements on [Yb(Cp)3], enabling quantification of the significant spin density at the C atoms of the Cp rings, which was discussed in terms of mixing of the 2 F7/2 ground term with low-lying charge-transfer states. More recently, some of us reported pulsed EPR studies of two An complexes, [An(Cp tt )3] (1-An; An = Th, U; Cp tt = C5H3 t Bu2-1,3), again showing significant spin density on the Cp tt ligands for both the U 3+ and Th 3+ analogues. Here we report pulsed EPR studies on a family of early Ln 3+ complexes [Ln(Cp tt )3] (1-Ln, Ln = La, Ce, Nd, Sm). This allows: (i) investigation of any trends across the series, from the "parent" diamagnetic, f 0 complex through the paramagnetic f 1,3,5 analogues. The latter are chosen because they are all Kramers ions and hence are expected to be EPR-active; (ii) comparison with the late Ln 3+ complex [Yb(Cp)3]; (iii) comparision of 1-Ln with the early An 3+ homologues 1-An. The latter includes direct comparison of the valence isoelectronic Nd 3+ (4f 3 ) and U 3+ (5f ) pair, which is the only comparison available between 4f and 5f M 3+ ions that does not require designated radiochemical laboratories (although Ce 3+ and Th 3+ have the same number of valence electrons, the Th 3+ ion favours the 6d 1 rather than 5f 1 configuration). Complexes 1-Ln are readily prepared by reacting LnCl3 with three equivalents of KCp tt ; 1-Ce and 1-Sm have been prepared previously by alternative synthetic routes, whilst 1-La and 1-Nd are structurally characterised here for the first time. We report the CW and pulsed EPR data for 1-Ce, 1-Nd and 1-Sm, along with the NMR data of diamagnetic 1-La. We quantify the hyperfine interaction in paramagnetic 1-Ln with ligand nuclei, originating from interaction with the Ln 3+ centres, and show that we can model these data using a simple point-dipole model. This is in agreement with fully-ab initio complete active space self-consistent field spin-orbit (CASSCF-SO) calculations that directly report hyperfine coupling parameters, as well as spin densities. We find, using either the simple or ab initio methods, that there is negligible spin density on the Cp tt ligands in 1-Ln, in contrast to unequivocal spin delocalisation in U 3+ and Th 3+ analogues [An(Cp tt )3], clearly highlighting the differences between early 4f and early 5f bonding in tris-Cp complexes. 9-13 Since the ability to perform such studies are limited by electron spin relaxation times, we also report relaxation data for 1-Ln by pulsed EPR methods. We find that 4f 1-Ln relax orders of magnitude faster than their 5f An analogues, despite preconceptions that relaxation rates increase for heavier elements due to increased spin-orbit coupling.