Electrochemical reduction of the unsaturated cyclic trinuclear Pd-3(dppm)(3)CO2+ cluster (dppm = ((C6H5)(2)P)(2)CH2)

Pd-3(dppm)(3)CO2+ exhibits a two-electron reduction process at similar to-0.5 V vs. SCE in 0.2 M Bu4NPF6 solutions of organic solvents such as dry acetonitrile, N,N-dimethylformamide (DMF), tetrahydrofuran (THF), and dichloromethane to reversibly produce the zero valent Pd-3(dppm)(3)CO, which exhibits a nu(CO) band in the 1761-1766 cm(-1) range in the IR spectra. The mechanistic aspects of this multistep two-electron process are discussed experimentally on the basis of r.d.e. (rotating disk electrode) voltammetry, cyclic voltammetry, and electrolysis results. Geometry optimizations using DFT (Density Functional Theory) predict that the Pd-Pd and C=O bond lengths are 3.008 and 1.182 Angstrom, respectively, which compare favorably with the experimental data for other zero valent polynuclear complexes.