Ureas react thermally with Ru3(CO)12 to give trinuclear complexes of the type (μ2-H)Ru3(CO)9(μ3- η2-R1NCONHR2) (1: R1 = R2 = H, 2: R1 = R2 = Me, 3: R1 = H, R2 = Ph, cis-4: R1 = H, R2 = cis-CHCHMe, trans-4: R1 = H, R2 = trans-CHCHMe). In the reaction of allylurea, the allylic double bond is displaced; the resulting complexes cis-4 and trans-4 contain a methylvinylurea ligand. The X-ray analysis of cis-4 shows the coordination of the urea moiety as a tripodal handle perpendicular to a nearly isosceles metal triangle. © 1992.