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We conducted a joint synthetic, spectroscopic and computational study to explore the reactivity towards cyanide (from Bu₄NCN) of a series of dinuclear complexes based on the M₂Cp₂(CO)₃ scaffold (M = Fe, Ru; Cp = η⁵-C₅H₅), namely [M₂Cp₂(CO)₂(µ-CO){µ,η¹:η²-CH=C=CMe₂}]BF₄ (<b>1Fe-Ru</b>), [Ru₂Cp₂(CO)₂(µ-CO){µ,η¹:η²-C(Ph)=CHPh}]BF₄ (<b>2Ru</b>) and [M₂Cp₂(CO)₂(µ-CO){µ-CN(Me)(R)}]CF₃SO₃ (<b>3Fe-Ru</b>). While the reaction of <b>1Fe</b> with Bu₄NCN resulted in prevalent allenyl deprotonation, preliminary CO-NCMe substitution in <b>1Ru</b> enabled cyanide addition to both the allenyl ligand (resulting in the formation of a h¹:h²-allene derivative, <b>5A</b>) and the two metal centers (affording <b>5B1</b> and <b>5B2</b>). The mixture of <b>5B1-2</b> was rapidly converted into <b>5A</b> in heptane solution at 100 °C, with <b>5A</b> being isolated with a total yield of 60%. Following carbonyl-chloride substitution in <b>2Ru</b>, CN⁻ was incorporated as a terminal ligand upon Cl⁻ displacement, to give the alkenyl complex <b>6</b> (84%). The reactivity of <b>3Fe</b> and <b>3Ru</b> is strongly influenced by both the metal element, M, and the aminocarbyne substituent, R. Thus, <b>7aRu</b> was obtained with a 74% yield from cyanide attack on the carbyne in <b>3aRu</b> (R = Cy, cyclohexyl), whereas the reaction involving the diiron counterpart <b>3aFe</b> yielded an unclean mixture of the metastable <b>7aFe</b> and the CO/CN⁻ substitution product <b>8aFe</b>. The cyano-alkylidene complexes <b>7aRu</b> (R = Cy) and <b>7bFe</b> (R = Me) underwent CO loss and carbene to carbyne conversion in isopropanol at 60–80 °C, giving <b>8aRu</b> (48%) and <b>8bFe</b> (71%), respectively. The novel compounds <b>5A</b>, <b>5B1-2</b>, <b>6</b> and <b>7aRu</b> were characterized by IR and NMR spectroscopy, with the structure of <b>7aRu</b> further elucidated by single crystal X-ray diffraction analysis. Additionally, the DFT-optimized structures of potential isomers of <b>5A</b>, <b>5B1-2</b> and <b>6</b> were calculated.