Functionalization of the terminal ruthenium carbide ligand in (Cy3P)2Cl2Ru≡C: with platinum and a range of ligands provides {Ru≡C−Pt−L} fragments with trans geometries. The bridging carbide exhibits chemical shifts and coupling constants to platinum, which are highly responsive to the degree of weakening of the RuC−Pt linkage induced by the trans ligands, making the terminal ruthenium carbide complex a sensitive probe for the electron donating abilities of other ligands.