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Abstract The study of actinide electronic structure and bonding within rigorously controlled environments is fundamental to advancing nuclear applications. Here, we report a new set of isostructural actinide organometallics; An(COT^big)₂, (An = Th, U, Np, and Pu), where COT^bigis the bulky 1,4-bis(triphenylsilyl)-substituted cyclooctatetraenyl dianion (1,4-(Ph₃Si)₂C₈H₆)^2-. The actinide(IV) metallocene sandwiches have a clam-shell structure, offering a new molecular symmetry to exploref-orbital contributions in bonding. Combined experimental and computational studies reveal that An(COT^big)₂complexes strongly differ from the previously published coplanar An(COT)₂sandwiches due to the bent geometry and electron-withdrawing nature of the substituents. While COT^bigdisplays comparatively weaker electron donation, the low-energyf-ftransitions in An(COT^big)₂have increased molar absorptivity consistent with the removal of the parity selection rule and better energetic matching between ligand and actinide 5forbitals as the series is traversed. For Pu(COT^big)₂, covalent mixing of donor 5fmetal orbitals and the ligand-π orbitals is especially strong.