The compound [Ru₃(CO)₁₂] reacts at room temperature in tetrahydrofuran with tri(2-pyridyl)phosphine, P(2-C₅H₄N)_3′ when catalysed by [N(PPh₃)₂]Cl, to give a product derived by cleavage of a phosphorus-2-pyridyl bond, [Ru₃(µ-2-C₅H₄N){µ₃-P(2-C₅H₄N)₂}(CO)₉]1. No simple substitution compounds could be isolated. The likely intermediates [Ru₃(CO)_n{P(2-C₅H₄N)₃}](n= 10 and/or 11) spontaneously decarbonylate while a 2-pyridyl group migrates from phosphorus to ruthenium atoms. A similar reaction using phenyldi(2-pyridyl) phosphine, PPh(2-C₅H₄N)_2′ leads to the competitive transfer of 2-pyridyl and pheyl groups to give almost equal quantities of two products, [Ru₃(µ-2-C₅H₄N){µ₃-PPh(2-C₅H₄N)}-(CO)₉] and [Ru₃(µ-PhCO){µ₃-P(2-C₅H₄N)₂}(CO)₉]. The crystal structure of 1 shows that the 2-pyridyl group that has migrated bridges two ruthenium atoms with no Ru-Ru bond between them and that the di(2-pyridyl) phosphido ligand is triply bridging with one nitrogen co-ordinated and one free. As in the reported reaction of [Ru₃(CO)₁₂] with PPh₂(2-C₅H₄N) to give [Ru₃(µ-PhCO){µ₃-PPh(2-C₅H₄N)}(CO)₉], the reason why P-C bond cleavage occurs under remarkably mild conditions and the mechanism of the processes have still to be determined.