Cyclisation of Allenylidene Ligands to Indenyl Groups on Ruthenium Clusters

Thermolysis of Ru-3 cluster complexes containing diarylallenylidene and dppm ligands results in phenyl migration from dppm to the allenylidene with concomitant H migration and C- C bond formation reactions to give several complexes each containing a cluster-bound indenyl group. In initially-formed complexes 3 or 6, the diarylindenyl group is attached to the cluster by two localized C=C double bonds of one aryl group and a benzylic interaction of the remaining C=C double bond combined with one carbon of the five-membered ring. Thermal rearrangement of these complexes with concomitant loss of CO gives 4 or 7, respectively, in which the indenyl group is more symmetrically bonded to the cluster by two C=C double bonds from the six-membered ring and an eta(5)-interaction from the five-membered ring, both of the indenyl ligand. The X-ray crystal structure determination of Ru-3(mu(3)-PPhCH2PPh2)(mu(3)-C9H5Ph2)(CO)(5) (4) is reported. A related reaction was found between Ru-3(mu-H)(mu-CCCPh2)(mu-OH)(CO)(9) and Co-2(CO)(8), which afforded CoRu3(mu(3)-C9H6Ph) (mu-CO)(4)(CO)(5) (8), also structurally characterized, in which the indenyl group caps the Ru-3 face of a CoRu3 tetrahedron; unusually, there are four CO groups bridging the three Co- Ru bonds.