Halogen photoreductive elimination from gold(III) centers

Area of Science:

• Inorganic Chemistry
• Photochemistry
• Organometallic Chemistry

Background:

• Gold(III) complexes are known to undergo ligand-to-metal charge transfer (LMCT) excitation.
• Halogen elimination from transition metal centers is a key reaction in various chemical processes.

Purpose of the Study:

• To investigate the photoelimination of halogen (X2) from monomeric and bimetallic gold(III) complexes.
• To explore the mechanism of M-X bond activation and halogen elimination upon LMCT excitation.
• To characterize the unprecedented multi-electron photoelimination pathways.

Main Methods:

• Synthesis of monomeric Au(III)(PR3)X3 and bimetallic Au2(I,III)[μ-CH2(R2P)2]X4/Au2(III,III)[μ-CH2(R2P)2]X6 complexes.
• Photochemical experiments involving LMCT excitation of gold complexes in solution.
• Analysis of halogen photoproduction using quantum yield measurements and in the absence/presence of chemical traps.

Main Results:

• Facile photoelimination of halogen (X2) was observed for both monomeric and bimetallic gold complexes.
• Unprecedented two-electron photoelimination of X2 from monomeric centers and four-electron photoelimination from bimetallic centers were achieved.
• Quantum yields for X2 photoproduction were consistently between 10% and 20%, with minimal dependence on ligand or nuclearity.
• Efficient, trap-free halogen elimination was demonstrated, a rare phenomenon for transition metal centers.

Conclusions:

• LMCT photochemistry of gold(III) complexes enables novel multi-electron photoelimination pathways for halogen.
• The observed efficient and trap-free halogen elimination offers new possibilities for synthetic applications.
• This work expands the understanding of photochemical reactivity in organometallic gold chemistry.