The dysprosium bis(amide) alkene complex 1-Dy and its diamagnetic yttrium analogue 1-Y were synthesised in 8-13% yields by protonation of the respective lanthanide bis(amide) allyl precursors [Ln{N(Si i Pr2Et)[Si( i Pr)2C(CH3)CHCH2]}2] (2-Ln; Ln = Dy, Y) with [HNEt3][Al{OC(CF3)3}4] in benzene at 40 °C for 18 h, and isolated by repeat fractional recrystallizations from fluorobenzene solutions layered with hexane (Figure ). A doped sample 5%Dy@1-Y was prepared by cocrystallisation of a mixture of 1-Dy and 1-Y. The allyl precursors (2-Ln) are synthesised in 15-17% yields via the reactions of parent LnI3 with [K{N(Si i Pr3)2}] in benzene at 100 °C (Figure ) as the sole benzene-soluble Ln-containing reaction products, by adapting literature protocols (see Supporting Information for further details). In these reactions, an in situ dehydrogenative C-C bond rearrangement of the ligand scaffold has occurred under the forcing conditions necessary for these salt metatheses.