Palladium Acetate Revisited: Unusual Ring-Current Effects, One-Electron Reduction, and Metal-Metal Bonding.

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Electrochemistry

Background:

• Palladium(II) acetate is a common precursor.
• New complexes of α,α,α',α'-tetramethyl-1,3-benzenedipropionate (esp^2-) were synthesized.

Purpose of the Study:

• To characterize novel palladium complexes (C_s-Pd₃(esp)₃ and C_3h-Pd₃(esp)₃) in solid and solution states.
• To investigate their electronic structure and electrochemical behavior.

Main Methods:

• Variable-temperature Nuclear Magnetic Resonance (NMR) spectroscopy
• Density Functional Theory (DFT) calculations
• Electrochemical reduction studies
• Electron Paramagnetic Resonance (EPR) spectroscopy

Main Results:

• NMR and DFT studies of C_s-2 revealed an unusual shielding region above palladium atoms.
• Compounds exhibited quasi-reversible reduction between -880 and -1200 mV versus Fc/Fc⁺.
• Electrochemical reduction yielded unprecedented, isostructural Pd₃⁵⁺ species.

Conclusions:

• The reduced palladium complexes possess a valence-trapped Pd^II-Pd^II-Pd^I electronic structure.
• EPR spectra with ¹⁰⁵Pd hyperfine coupling confirmed the proposed electronic configuration.
• These findings represent a novel electronic state in palladium cluster chemistry.