Cyclisation of Allenylidene Ligands to Indenyl Groups on Ruthenium Clusters

Abstract

Thermolysis of Ru3 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 η 5-interaction from the five-membered ring, both of the indenyl ligand. The X-ray crystal structure determination of Ru3(μ 3-PPhCH2PPh2)(μ 3-C9H5Ph2)(CO)5 (4) is reported. A related reaction was found between Ru3(μ-H)(μ-CCCPh2)(μ-OH)(CO)9 and Co2(CO)8, which afforded CoRu3(μ 3-C9H6Ph) (μ-CO)4(CO)5 (8), also structurally characterized, in which the indenyl group caps the Ru3 face of a CoRu3 tetrahedron; unusually, there are four CO groups bridging the three Co–Ru bonds.