The first structurally confirmed paddlewheel compound with an M(2)(7+) core: [Os(2)(hpp)(4)Cl(2)](PF(6))

Area of Science:

• Inorganic Chemistry
• Materials Science
• Coordination Chemistry

Background:

• Paddlewheel complexes are crucial in coordination chemistry.
• Understanding metal-metal bonding in osmium compounds is an active research area.
• The hexahydropyrimidopyrimidine (hpp) ligand offers unique electronic and steric properties.

Purpose of the Study:

• To synthesize and characterize a novel osmium paddlewheel complex.
• To investigate the electronic structure and properties of a metal-metal bonded M(2)(7+) core.
• To explore higher oxidation states of dinuclear osmium complexes.

Main Methods:

• Oxidation of Os(2)(hpp)(4)Cl(2) using (FeCp(2))PF(6).
• X-ray crystallography to determine Os-Os bond distances in different crystalline forms.
• Electron Paramagnetic Resonance (EPR), proton Nuclear Magnetic Resonance ((1)H NMR), and magnetization studies.
• Electrochemical analysis to probe oxidation states.

Main Results:

• Synthesis of air-stable [Os(2)(hpp)(4)Cl(2)]PF(6) (2), the first structurally confirmed M(2)(7+) paddlewheel compound.
• Os-Os distances of 2.3309(4) Å (2•2acetone) and 2.3290(6) Å (2•hexane).
• EPR, (1)H NMR, and magnetization data confirm an unpaired electron and a low g value (0.791 ± 0.037).
• Electrochemical study revealed a quasireversible wave indicating an Os(2)(8+) core.

Conclusions:

• The study reports the first structurally confirmed dinuclear osmium paddlewheel complex with an M(2)(7+) core.
• The compound exhibits unique electronic properties, including an unpaired electron and an exceptionally low g value.
• The electrochemical data suggest the accessibility of an unprecedented Os(2)(8+) oxidation state, opening avenues for further redox studies.