SYNTHESIS AND REACTIONS OF DIRECTLY BONDED ZIRCONIUM-RUTHENIUM HETEROBIMETALLIC COMPLEXES

The directly bonded zirconium-ruthenium heterobimetallic compounds Cp2(X)ZrRu(CO)2Cp (X = Cl, OCMe3, CH3, CH2CH3) were synthesized by reaction of Cp2(X)ZrCl with K+ Cp(CO)2Ru-. The zirconium-diruthenium compound Cp2Zr[Ru(CO)2Cp]2 (21) was synthesized by reaction of Cp2ZrI2 with K+ Cp(CO)2Ru-. Reaction of 21 with a variety of ligands led to expulsion of Cp(CO)2RuH and formation of C5H4-Zr products or intermidiates. Reaction of 21 with CO produced Cp2(CO)Zr(mu-eta-1,eta-5-C5H4)Ru(CO)2 (22), with PMe3 produced Cp2Zr(mu-CO)(mu-eta-1,eta-5-C5H4)Ru(CO)(PMe3) (23), and with CH2 = CH2 produced Cp2Zr(mu-CH2CH2C5H4)Ru(CO)2 (26). All three these reactions are 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 Cp2Zr(mu-eta-1,eta-5-C5H4)Ru(CO)2 (I). The reaction of the CO adduct 22 with H-2 led to hydrogenolysis of the Zr-C5H4 bond and to the formation of Cp2Zr(mu-CO)(mu-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.