Tricarbonyl[9-(triphenylphosphonio)fluorenylidene]ruthenium, [Ru(C31H21P)(CO)3], (I), is mononuclear, consisting of a single Ru centre, to which three carbonyl units and a chelating μ3-9-(triphenylphosphonio)fluorenide ylide bind to generate a distorted octahedral RuC6 core. Nonacarbonyl-μ3-fluorenylidene-μ2-hydrido-triangulo-triosmium(III), [Os3H(C13H7)(CO)9], (II), is trinuclear and presents a triangular triosmium core, nine carbonyl ligands and one fluorenylidene ligand. Two of the Os(III) centres present a highly distorted hexacoordinated Os(Os2C4) core and are in turn bridged by a hydride ligand. The remaining Os(III) cation is octacoordinated, with an Os(Os2C6) nucleus. The crystal structures of both compounds are the result of nondirectional forces, much resembling the packing of weakly interacting quasi-spherical units, viz. the molecules themselves in (I) and centrosymmetric π-π-bonded dimers in (II).