The directly bonded zirconiumruthenium heterobimetallic compounds Cp 2(X)ZrRu(CO) 2Cp ( X = Cl, OCMe 3, CH 3, CH 2CH 3) were synthesized by reaction of Cp 2(X)ZrCl with K + Cp(CO) 2Ru −. The zirconiumdiruthenium compound Cp 2Zr[Ru(CO) 2Cp] 2 ( 21) was synthesized by reaction of Cp 2ZrI 2 with K +Cp(CO) 2Ru −. Reaction of 21 with a variety of ligands led to expulsion of Cp(CO) 2RuH and formation of C 5H 4-Zr products or intermediates. Reaction of 21 with CO produced Cp 2(CO)Zr(μ-η 1,η 5- C 5H 4)Ru(CO) 2 ( 22), with PMe 3 produced Cp 2Zr(μ-CO)(μ-η 1,η 5-C 5H 4)Ru(CO)(PMe 3) ( 23), and with CH 2CH 2 produced Cp 2Zr(μ-CH 2CH 2C 5H 4)Ru(CO) 2 ( 26). All three of these reactions proceeded at the same rate which was independent of incoming ligand concentration. All three reactions are proposed to involve rate determining formation of the reactive intermediate Cp 2Zr(μ-η 1,η 5-C 5H 4)Ru(CO) 2 ( I). The reaction of CO adduct 22 and H 2 led to hydrogenolysis of the ZrC 5H 4 bond and to the formation of Cp 2Zr(μ-CO)(μ-OCH)Ru(CO)Cp ( 32). Labelling studies demonstrated that reversible formation of both zirconium formyl and ruthenium formyl intermediates occurs during the reduction of 22 to 32.