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).