UltimSMM project proposes original synthetic pathways to generate ideal lanthanide-based sandwich metallocene complexes towards ground-breaking insights into the field of lanthanide Single Molecule Magnets (SMMs). Bulky cyclopentadienyl-based trivalent dysprosium complexes have recently led to impressive progress in the field of lanthanide SMMs, however, so far the perfect geometry has not been obtained in these sandwich complexes (Cp-Dy-Cp angle of 180°). This project aims to synthesize such unprecedented linear trivalent complexes based on pentaarylcyclopentadienyl ligands starting from zero-valent lanthanides and exploring straightforward C-FG bond cleavage (FG = P, Si, halides) routes driven by prospective quantum chemical calculations. The reactions will be performed in solution or, for the first time, under solvent-free ball-milling techniques. Variation of the aryl groups, introduction of heteroelements in the cyclopentadienyl ring and employing lanthanide metals beyond dysprosium are among the target modifications, providing complexes designed to lead the race in the field of high-temperature nanomagnets.