Abstract:

The highly reactive palladium-centered radical cluster [Pd-3(dpPM)(3)(CO)](center dot+) exhibits only a limited stability in solution at room temperature (about an hour). This stability can be extended significantly to several hours by adding organic substrates such as the symmetric and asymmetric alkynes Ph-C C-H and MeO2C-C C-CO2Me, which reversibly bind to the Pd-3 triangle. The presence of the substrate inside the cavity protects the palladium centers from reacting with the "outside world", hence enhancing the stability. Both adducts are stable as the cluster is always totally recovered. The paramagnetic complexes along with their corresponding dications were characterized by EPR, variable-temperature P-31 NMR, UV-vis and MALDI-TOF spectroscopy, and electrochemistry. For the MeO2C-C C-CO2Me/[Pd-3-(dppm)(3)(CO)](2+) complex, the analysis of the low-temperature P-31 NMR spectra strongly suggests a major structure modification of the ligand and substrate with respect to the starting materials.

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Times Cited: 4Dal Molin, Sophie Cugnet, Cyril Brevet, David Lucas, Dominique Mugnier, Yves Fortin, Daniel Boere, Rene T. Harvey, Pierre D.

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