Ruthenium−aminoallenylidene complexes trans-[Cl(L2)2RuCCC(NR2)CH2R‘]+EF6- (4a−f; E = P, Sb, L2 = chelating diphosphine) are accessible from the respective dichloro precursors, NaEF6, butadiyne, and an allylic amine in a one-pot procedure. The reactions proceed via the primary butatrienylidene intermediate trans-[Cl(L2)2RuCCCCH2]+ and the initial addition products trans-[Cl(L2)2Ru−C⋮CC(NR2R‘)CH2]+ via an Aza-Cope type rearrangement. Amine adducts have been isolated for (dimethylamino)-2-pentyne (3f) and 1-methyl-1,2,5,6-tetrahydropyridine (3g). The former cleanly converts to its aminoallenylidene isomer upon warming. All products have been characterized by various spectroscopic techniques, including NMR, IR, and UV/vis spectroscopy and cyclic voltammetry; complex 4b was also characterized by X-ray crystallography. Most notable are the considerable bond length alternations along the unsaturated C3 ligand and the trigonal-planar nitrogen, indicative of its sp2 character. Aminoallenylidene complexes of this t...