Synthesis and properties of IrRe2(mu-H)(2)(CO)(9)(eta(5)-C9H7)

The slow addition of Re-2(mu-H)(2)(CO)(8) to a solution of Ir(CO)(eta(2)-C8H14)(eta(5)-C9H7) in hexane at reflux provides IrRe2(mu-H)(2)(CO)(9)(eta(5)-C9H7) (1) in 80% yield. The molecular structure of 1 shows an IrRe2 triangle incorporating one Ir(CO)(eta(5)-C9H7) and two Re(CO)(4) fragments. The strongly different Ir-Re distances suggest that one hydride ligand bridges one IT-Re edge and the other hydride bridges the Re-Re edge, Low-temperature H-1 and C-13 NMR spectra are consistent with this structure; at higher temperatures a dynamic process involving migration of one hydride ligand between the two Ir-Re edges is observed. Cluster 1 is readily deprotonated with KOH/EtOH, and the resulting anion has been isolated as the PPN salt, [PPN][IrRe2(mu-H)(CO)(9)(eta(5)-C9H7)] (2) Both the H-1 and low temperature C-13 NMR spectra of 2 are consistent with a structure in which the remaining hydride ligand bridges the Re-Re edge. Variable-temperature C-13 NMR spectra indicate that 2 undergoes CO scrambling localized on the Ir-Re edges. The reaction of 1 with PPh3 leads to IrRe2(mu-H)(2)(CO)(8)(PPh3)(eta(5)-C9H7) (3), which contains the phosphine on a rhenium atom, as well as to cluster fragmentation.