| Abstrakt: |
The triruthenium cluster HRu3(CO)9(μ3,η2,η2,η1-C&tbd1;CPh) (1) reacts with the diphosphine ligand bpcd in the presence of Me3NO to afford the new cluster compounds HRu3(CO)7(bpcd)(μ3,η2,η2,η1-C&tbd1;CPh) (2) and HRu3(CO)7[μ3,η2,η2,η1,η1,η1-Ph2PC&dbd;CC(O)CH2C(O)PPh2C&dbd;CPh] (3). Cluster 2 is the sole product from the controlled thermolysis of 1 with bpcd. Both 2 and 3 have been isolated and characterized in solution by IR and NMR (1H and 31P) spectroscopies, and by X-ray crystallography in the case of the latter cluster. The bpcd ligand in 2 chelates to the ruthenium center that is σ bound by the acetylide ligand, and in the zwitterionic compound 3 one of the PPh2 moieties of the bpcd ligand coordinates to a hydride-bridged ruthenium atom while the other PPh2 group exists as a phosphonium center due to attack on the acetylide Cα carbon. Whereas 3 slowly decomposes in solution at elevated temperatures, cluster 2 was found to undergo a clean conversion to the new cluster Ru3(CO)7(μ,η2,η1-PhC&dbd;CHPh)[μ2,η2,η1-PPhC&dbd;CC(O)CH2C(O)PPh2] (4). The bridging alkenyl ligand in 4 results from the formal cleavage of one of the P−Ph bonds of the bpcd ligand, followed by the concomitant coupling of the phenyl and hydride groups with the acetylide ligand. Cluster 4 has been fully characterized in solution and the solid-state structure established by X-ray analysis. NMR data are presented from a labeling study employing HRu3(CO)7(bpcd)(μ3,η2,η2,η1-C&tbd1;Ctol-p) that shows that the hydrogen in the μ,η2,η1-RC&dbd;CHR moiety of Ru3(CO)7(μ,η2,η1-RC&dbd;CHR)[μ2,η2,η1-PPhC&dbd;CC(O)CH2C(O)PPh2] is distributed between both the phenyl and tol-p groups. The scrambling of the alkenyl hydrogen between the phenyl- and tol-p-substituted carbon atoms in the μ,η2,η1-RC&dbd;CHR moiety suggests that hydride transfer from the triruthenium frame occurs via a transient cluster compound that possesses a coordinated PhC&tbd1;Ctol-p ligand. |
